فهرست مطالب

  • سال پانزدهم شماره 2 (پیاپی 56، خرداد و تیر 1398)
  • تاریخ انتشار: 1398/03/19
  • تعداد عناوین: 12
|
  • فاطمه حبیبی نوده، رضا فرهوش*، علی شریف صفحات 235-243
    در این تحقیق، شاخص پایداری اکسایشی روغن (OSI) و دوره القا ترکیبات کربونیلی (IPCV) و زمان پایداری سرخ کردن(tf cv =47) (زمان مورد نیاز جهت رسیدن به حد بحرانی 47 میکرومول بر گرم ترکیبات کربونیلی) یک مجموعه ای از روغن های زیتون به ترتیب در دو شرایط فرآیند حرارتی (آزمون رنسیمت در دماهای 110 تا140 درجه سانتی گراد) و فرآیند سرخ کردن در 180 درجه سانتی گراد بررسی گردید. همبستگی خوبی               (R2= 0.9963) بین شاخص پایداری اکسایشی (OSI) و دوره القا ترکیبات کربونیلی (IPCV) در آزمون حرارتی رنسیمت، مشاهده گردید. در دماهای مشابه آزمون رنسیمت، شاخص پایداری اکسایشی نمونه های روغن تفاوت معنی داری را نشان داد. بیشترین و کمترین OSI و IPcv به ترتیب در نمونه های 6 و 1 مشاهده گردید. با بالا رفتن درجه حرارت، سرعت اکسایش نمونه های مورد مطالعه افزایش و شاخص های پایداری اکسایشی کاهش یافت. بیشترین همبستگی (R2= 0.9985) از رسم زمان های پایداری سرخ کردن (tfcv=47) در مقابل IPcv در 110 درجه سانتی گراد به دست آمد و با افزایش دما تا 140 درجه سانتی گراد میزان این همبستگی کاهش یافت که این مسئله می تواند به تفاوت مکانیسم های اکسایش لیپیدی در دمای بالا و پائین مرتبط باشد.
    کلیدواژگان: سرخ کردن، روغن زیتون، پایداری اکسایشی، رنسیمت
  • مریم عین علی افجه، رضوان پوراحمد*، بهروز اکبری آدرگانی، مهرداد آذین صفحات 245-255
    هدف از این تحقیق بررسی اثر افزودن گلوکز اکسیداز تثبیت شده بر روی نانوذرات مغناطیسی کیتوزان بر مقدار اسیدهای آلی (اسید لاکتیک و اسید استیک)، زنده مانی باکتری های پروبیوتیک و ویژگی های حسی ماست نوشیدنی پروبیوتیک بود. مقادیر مختلف (صفر، 250، 500، 750 و1000 میلی گرم بر کیلوگرم) گلوکز اکسیداز آزاد و تثبیت شده در ماست نوشیدنی پروبیوتیک استفاده شد. نمونه ها به مدت سه هفته در دمای 4 درجه سلسیوس نگهداری شدند. طی زمان نگهداری مقدار اسید استیک، جمعیت لاکتوباسیلوس اسیدوفیلوس و بیفیدوباکتریوم لاکتیس به طور معنی داری کاهش یافت ولی مقدار اسید لاکتیک افزایش معنی داری داشت (05/0>p). افزودن آنزیم باعث افزایش زنده مانی باکتری های پروبیوتیک در نمونه های تست در مقایسه با نمونه شاهد (فاقد آنزیم) شد. زنده مانی بیفیدوباکتریوم لاکتیس در نمونه های حاوی سطوح بالای آنزیم (750 و 1000 میلی گرم بر کیلوگرم) کمتر از سایر سطوح بود. نمونه های حاوی 500 میلی گرم برکیلوگرم آنزیم آزاد و تثبیت شده بالاترین تعداد بیفیدوباکتریوم لاکتیس (log CFU/mL88/7) را داشتند و مقدار اسید استیک در این نمونه ها بیشتر بود (به ترتیب 82/0 و g/L 87/0). تفاوت معنی داری در ویژگی های حسی نمونه ها مشاهده نشد. بنابراین افزودن گلوکزاکسیداز تثبیت شده بر روی نانو ذرات مغناطیسی کیتوزان می تواند با کاهش فشار اکسیداتیو شرایط مطلوب تری را برای بقای باکتری های پروبیوتیک در ماست نوشیدنی پدید آورد و پذیرش کلی حسی محصول را حفظ نماید ضمن اینکه از نظر اقتصادی نیز مقرون به صرفه است.
    کلیدواژگان: کیتوزان، گلوکز اکسیدازتثبیت شده، ماست نوشیدنی پروبیوتیک، نانوذرات مغناطیسی
  • زهره دیدار* صفحات 257-266
    در این تحقیق، سنتز نانوذرات ترکیبی منگنز- اکسید روی، آهن- اکسید روی به روش رسوب همزمان و بررسی ویژگی های ساختاری و مورفولوژیکی نانوذرات حاصله با استفاده از طیف مادون قرمز فوریه، پراش اشعه X و میکروسکوپ الکترونی عبوری صورت گرفت. بررسی ها نشان داد که عمل ترکیب عناصر منگنز و آهن توسط روش رسوب همزمان بر روی نانوذرات اکسید روی به خوبی توسط روش رسوب همزمان صورت می گیرد. به منظور بررسی اثرات ضدمیکروبی نانوذرات ترکیبی مورد نظر، از روش قطر هاله عدم رشد و حداقل غلظت بازدارندگی در برابر باکتری باسیلوس سرئوس (PTCC 1665) استفاده شد. نتایج آزمون های اثرات ضدمیکروبی نشان داد که نانوذرات ترکیبی منگنز- اکسید روی اثرات ضدمیکروبی بیشتری بر روی باسیلوس سرئوس نسبت به آهن- اکسید روی دارد و ایجاد قطر هاله عدم رشد برابر با 32 میلی متری ایجاد می کند در حالی که آهن- اکسید روی، قطر هاله عدم رشد 12 میلی متر است. بعلاوه هر دو نانوذره ترکیبی اثرات ضدمیکروبی بیشتری نسبت به نانوذرات اکسید روی به تنهایی ایجاد می کنند و در نتیجه عمل ترکیب این عناصر در ساختار اکسید روی سبب بهبود خاصیت ضدمیکروبی آن می گردد. در مقایسه اثرات سینرژیست نانوذرات ترکیبی با دو ماده ضدمیکروبی متداول شامل پراکسید هیدروژن و هیپوکلریت سدیم مشخص گردید که هر دو این نانوذرات با این ترکیبات ضد میکروبی اثر هم افزایی و سینرژیست دارند(به خصوص در غلظت های بالا).
    کلیدواژگان: نانوذرات ترکیبی، اکسید روی، سینرژیست، باسیلوس سرئوس
  • ادریس آرژه، میرخلیل پیروزی فرد*، سجاد پیرسا صفحات 267-279
    شربت خام به عنوان یک محصول حد واسط در فرآوری چغندرقند حاوی ناخالصی های مختلفی (مانند پروتئین، ساپونین، ترکیبات رنگی، ترکیبات فنلی، پکتین و...) است که بایستی جداسازی یا به یک سطح قابل قبول کاهش داده شوند تا شربت برای مراحل بعد آماده سازی گردد. در این پژوهش از چهار ماده مختلف شفاف کننده (بنتونیت، سیلیکا سل، ژلاتین و زغال فعال) برای حذف ناخالصی شربت خام چغندر استفاده گردید. از مقایسه بنتونیت با سیلیکا سل به عنوان دو ترکیب با بار سطحی منفی مشخص شد که توانایی بنتونیت در حذف ناخالصی های عامل فلوک (پروتئین، ساپونین و ترکیبات فنولی) و بهبود شاخص های تصفیه ای (خاکستر و درجه خلوص) به مراتب بالاتر از سیلیکا سل است. به طوری که تیمار بنتونیتی توانست میزان پروتئین، ترکیبات فنولی و ساپونین ها در شربت را به ترتیب 68، 61 و 40 درصد کاهش دهد. ترکیب ژلاتین و زغال فعال به عنوان شفاف کننده های مکمل با بنتونیت و سیلیکا سل هم موجب بهبود پارامترهای مورد اندازگیری شد. به طور کلی تیمار بنتونیت- زغال فعال بهترین نتیجه را در بر داشت و به ترتیب موجب کاهش 73، 87 و 85 درصدی در میزان پروتئین، ترکیبات فنولی و ساپونین ها شد. در این پژوهش همچنین تیمارهای پیشنهاد شده با تیمار متداول (آهک-دی اکسید کربن) مورد مقایسه قرار گرفتند و مشخص شد که این تیمارها توانایی بهتری جهت حذف حداکثری ناخالصی ها دارند.
    کلیدواژگان: شربت خام چغندر، تصفیه شیمیایی، بنتونیت، سیلیکا سل، ژلاتین، زغال فعال
  • آتوسا عصارزادگان، محمد فاضل* صفحات 281-296
    عوامل مخرب میکروبی، شیمیایی و مکانیکی منجر به کاهش عمر مفید برش های میوه به می گردد. بدین منظور از پوشش کیتوزان، عصاره علف لیمو و پیش تیمار بلانچینگ و آبگیری اسمزی استفاده شد.هدف از این مطالعه بررسی تاثیر پوشش کیتوزان حاوی عصاره علف لیمو بر روی ماندگاری برش های میوه به آبگیری شده است. پس از بلانچ کردن نمونه، به ترتیب فرآیند آبگیری اسمزی و پوشش دهی انجام شد و تیمارها در دمای یخچال (1±4 درجه سانتی گراد) به مدت 4 هفته نگهداری شدند. آزمایش به صورت فاکتوریل بر پایه طرح کاملا تصادفی در 3 تکرار انجام شد. متغیرها شامل نوع محلول اسمزی (ساکارز، سوربیتول) و تیمارهای پوششی (پوشش کیتوزان حاوی صفر، 5/0، 1 و 2 درصد عصاره علف لیمو) است. ویژگی های مورد بررسی شامل کاهش وزن (%)، اسیدیته، pH، غلظت اسید آسکوربیک، خواص رنگی (مولفه های L*، a* وb*)، بافت، فنول کل، فعالیت آنتی اکسیدانی کل بود که در هفته اول، دوم، سوم و چهارم بررسی شد. در این مطالعه بالاترین میزان فعالیت آنتی اکسیدانی کل، اسید آسکوربیک، فنول کل، اسیدیته و کمترین میزان افت وزن مربوط به پوشش کیتوزان حاوی 2 درصد عصاره علف لیمو بود. افزایش غلظت عصاره موجب کاهش a* (قرمزی) و L* (روشنایی) میوه به شد. در به پوشش داده شده با کیتوزان میزان نرم شدگی به دلیل تنفس و فعالیت آنزیمی کمتر میوه محسوس نبوده است. بر اساس نتایج حاصله از این مطالعه، پوشش خوراکی حاوی 2 درصد عصاره علف لیمو به عنوان بهترین فرمول حاصله پیشنهاد می شود.
    کلیدواژگان: عصاره علف لیمو، کیتوزان، برشهای میوه به، آبگیری اسمزی، پوششهای خوراکی
  • سارا آقاجان زاده سورکی، امان محمد ضیایی فر*، مهدی کاشانی نژاد، عباس رضایی اصل صفحات 297-307
    امروزه، میدان الکتریکی پالسی (PEF) به عنوان روشی نوین جهت سالم سازی و افزایش مدت زمان ماندگاری آب میوه ها مورد استفاده قرار می گیرد. آنزیم پکتین متیل استراز (PME) به دلیل دارا بودن مقاومت حرارتی بالا به عنوان شاخص کفایت فرآوری آب میوه ها با اسیدیته بالا، مانند آب گوجه فرنگی، شناخته می شود. با توجه به ساختار پروتئینی این آنزیم، افزایش دمای اولیه آب میوه قبل از فرآوری PEF، به غیرفعال سازی بیش تر آن و در نتیجه افزایش کارایی این روش کمک می کند. روش  نوین حرارت دهی سریع مواد غذایی با استفاده از امواج مادون قرمز (IR) در کاهش میزان افت مواد مغذی موثر شناخته می شود. از این رو، در این پژوهش به تاثیر همزمان دو فرایند حرارتی (IR) و غیرحرارتی (PEF) بر برخی از ویژگی های فیزیکوشیمیایی آب گوجه فرنگی پرداخته شد. برای این منظور، ابتدا آب گوجه فرنگی با استفاده از امواج IR تا دماهای 40، 45 و 50 درجه سانتی گراد حرارت دهی شد. سپس، نمونه تحت فرایند PEF مداوم (73/22، 27/27، 82/31 و 36/36 کیلوولت بر سانتی متر به مدت 3520 میکروثانیه) قرار گرفت. میزان تغییرات اسید اسکوربیک، آنزیم پکتین متیل استراز (PME)، کدورت و رنگ آب گوجه فرآوری شده به ترتیب با استفاده از روش های یدومتری، کیم بال، اسپکتوفوتومتری و پردازش تصویر تعیین گردید. نتایج نشان داد که پیش حرارت دهی آب میوه در کنار وقوع پدیده حرارت دهی اهمیک طی فرایند PEF، به دلیل افزایش بسیار سریع دمای آب گوجه فرنگی موجب کاهش بیش تر میزان فعالیت آنزیم و افزایش کدورت محصول شد. همچنین، مشاهده شد که با ترکیب PEF و حرارت دهی ملایم و سریع محصول می توان موجب کاهش میزان افت محتوای اسید اسکوربیک و جلوگیری از بروز تغییرات نامطلوب رنگ نمونه شد.
    کلیدواژگان: امواج مادون قرمز، میدان الکتریکی پالسی، آب گوجهفرنگی، اسید اسکوربیک، آنزیم پکتین متیلاستراز، خصوصیات رنگی
  • حسام عمرانی فرد، مهدی خجسته پور*، علی دشتی، محمدحسین عباس پور فرد صفحات 309-322
    در این مطالعه، سینتیک تخریب حرارتی دینامیکی بیوپلاستیک تهیه شده از آمیخته ژلاتین پای مرغ- آرد کامل سیب زمینی و نمونه شاهد که متشکل از آرد کامل سیب زمینی بود، مورد بررسی و مقایسه قرار گرفتند. ژلاتین استفاده شده در این مطالعه از نوع مرغی بود که با استفاده از روش های شیمیایی از پای مرغ استخراج شد. در این پژوهش دو مدل ایزوکانورژنال انتگرالی شامل مدل فلین- وال- اوزاوا (FWO) و کیسینجر- آکاهیرا- سانوز (KAS) در نظر گرفته شد که با استفاده از هر کدام از این مدل ها، پارامتر های سینتیک تخریب حرارتی شامل انرژی فعال سازی و ضریب بسامد برای نمونه های بیوپلاستیک محاسبه گردید. نتایج نشان داد که بیشینه ی انرژی فعال سازی محاسبه شده برای بیوپلاستیک آمیخته (GC) به روش FWO در نسبت تبدیل 9/0 و برابر kJ/mol162 و پس از آن در نسبت تبدیل 5/0 و برابر kJ/mol150 است، در حالی که بیشینه انرژی فعال سازی بیوپلاستیک شاهد (P) در نسبت تبدیل 6/0 و برابر kJ/mol217 مشاهده شد. مقادیر بدست آمده برای ضریب بسامد نیز نشان داد این پارامتر بین 1/min1014×27/1 تا 1/min104×25/1 برای بیوپلاستیک آمیخته و برای بیوپلاستیک شاهد بین 1/min1014×94/1 تا 1/min104×82/1 بسته به تغییرات نسبت تبدیل و نرخ های مختلف گرمادهی، تغییر می کند.
    کلیدواژگان: انرژی فعالسازی، بیوپلاستیک، ژلاتین، سیبزمینی، سینتیک تخریب حرارتی
  • محمد ابراهیم گوهرجو، محمدرضا عدالتیان دوم*، فخری شهیدی، فریده طباطبایی یزدی، محمد جواد وریدی صفحات 323-339
    هویج تخمیری نوعی شوری تهیه شده از هویج و نمک است که سرشار از ویتامین ها می باشد. هدف از این پژوهش، بررسی تنوع زیستی باکتری های اسید لاکتیک فرآورده طی دوره نگهداری و رسیدگی بود. بدین منظور پس از تولید هویج تخمیری، تنوع باکتری های اسید لاکتیک موجود در فرآورده در شش تناوب زمانی بررسی گردید. 144 جدایه گرم مثبت و کاتالاز منفی، جداسازی شده که از میان آنها، 48 جدایه گرم مثبت و کاتالاز منفی انتخاب شدند. آزمون های فیزیولوژیکی و بیوشیمیایی شامل رشد در دماهای 10 و 45 درجه سانتی گراد، در 5/6 درصد نمک طعام، در 4/4 =pH و 6/9 pH=، وتولید گاز دی اکسیدکربن از قند گلوکز انجام پذیرفت. در مرحله بعد، شناسایی بر اساس پروفایل تخمیر کربوهیدرات (ده قند)، منجر به شناسایی جنس های پدیوکوکوس (2 مورد)، لویکونوستوک (10 مورد)، لاکتوباسیلوس (33 مورد) و انتروکوکوس (2 مورد) و یک مورد هم شناسایی نگردید و در مجموع 19 گونه مختلف گردید. در پایان، 26 جدایه از مجموع 48 جدایه توسط تعیین توالی ژن 16S rDNA تا سطح جنس و گونه شناسایی شدند. نتایج توالی یابی منجر به شناسایی گونه های ذیل گردید: Lactobacillus plantarum (34/33%)، Leuconostoc mesenteroides (85/14%) ،Lactobacillus.brevis (63/29%)، Lactobacillus.casei (7/3%)، Lactobacillus.pantheris (7/3%)، Lactobacillus paracasei (7/3%) و سه ایزوله تا مرحله جنس به عنوان لاکتوباسیلوس شناسایی شدند. لویکونوستوک مزنترویدس در مراحل اولیه تخمیر با توجه به نتایج توالی یابی و مولکولی غالب بوده که به تدریج در مراحل پایانی توسط لاکتوباسیلوس برویس جایگزین گردید. آنالیز فیلوژنتیک وجود سه خوشه را نشان داد، به طوریکه خوشه اول شامل دو جنس لوکونستوک و لاکتوباسیلوس، خوشه دوم شامل لاکتوباسیلوس برویس و خوشه سوم شامل لاکتوباسیلوس پلانتاروم بوده است.
    کلیدواژگان: تنوع زیستی، باکتریهای اسید لاکتیک، هویج، تخمیر، فیلوژنی
  • محسن آزادبخت*، محمد جواد محمودی، محمد واحدی ترشیزی صفحات 341-353
    ارزیابی کیفیت میوه ها و سبزیجات با استفاده از روش های غیرمخربی نظیر سی تی اسکن از جمله پرکاربردترین روش های ارزیابی می باشد. لذا در این پژوهش، مقدار کوفتگی گلابی در اثر بارگذاری دینامیکی و ارتباط آن با حجم و وزن گلابی طی دوره انبارمانی با استفاده از روش غیرمخرب سی تی اسکن مورد بررسی قرار گرفت. قبل از بارگذاری تعداد 50 گلابی با استفاده از سی تی اسکن بررسی شده و تعداد 27 گلابی با درصد پوسیدگی صفر انتخاب شدند. تحت بارگذاری دینامیکی با استفاده از یک آونگ با سه وزنه 300، 350 و 400 گرمی قرار داده شد و به منظور بررسی حجم کل و حجم پوسیدگی نمونه ها، در دوره های انبارمانی 5، 10 و 15 روز، تصویرگیری با استفاده از سی تی اسکن نیز انجام شد. نتایج حاکی از آن بود که با افزایش حجم گلابی، درصد پوسیدگی کاهش پیدا کرد و برخلاف آن با افزایش وزن گلابی، مقدار درصد پوسیدگی نیز افزایش یافت. همچنین بین درصد کاهش حجم و وزن با درصد پوسیدگی یک رابطه مستقیم وجود داشت بدین صورت که با افزایش درصد کاهش حجم و وزن درصد پوسیدگی افزایش پیدا کرد. بنابراین می توان نتیجه گرفت هرچه تغییرات حجم و وزن قبل و بعد از ضربه کمتر باشد میوه سالم تر بوده و درصد پوسیدگی کمتر خواهد بود.
    کلیدواژگان: گلابی، سیتیاسکن، غیرمخرب، کوفتگی، حجم
  • ناهید جعفری، سید حمیدرضا ضیاءالحق*، عبدالرضا محمدی نافچی صفحات 355-367
    در این تحقیق، تاثیر پیش تیمار اسمزی بر ویژگی های کیفی و خصوصیات حسی خلال های سیب زمینی خشک شده مورد بررسی قرار گرفت. محتوای رطوبت، ظرفیت بازجذب آب، چروکیدگی، قهوه ای شدن، شاخص های رنگی و خصوصیات حسی (طعم، رنگ، شکل ظاهری، استحکام و پذیرش کلی) نمونه های سیب زمینی پس از فرآیند خشک کردن ارزیابی شده و از روش سطح پاسخ (RSM) جهت تعیین شرایط بهینه پیش تیمارهای آبگیری اسمزی، با هدف بالاترین امتیازات خواص فیزیکوشیمیایی و حسی، استفاده شد. نتایج نشان داد که با افزایش زمان پیش تیمار اسمزی، محتوای رطوبت، قهوه ای شدن و امتیازطعم به تدریج افزایش یافت، در حالی که بازجذب آب کاهش پیدا کرد (p<0.05). زمان پیش تیمار اسمزی اثر معنی داری بر شاخص های رنگی نمونه های سیب زمینی نداشت (p>0.05). با افزایش غلظت محلول اسمزی، میزان رطوبت، چروکیدگی، بازجذب آب، قهوه ای شدن و شاخص زردی (b*) کاهش یافت (p<0.05). با افزایش دمای محلول اسمزی میزان چروکیدگی، روشنایی و امتیاز طعم نمونه ها افزایش و میزان قرمزی و تغییر رنگ کلی خلال های سیب زمینی کاهش یافت (p<0.05). نتایج ارزیابی حسی نشان داد که تغییرات غلظت، زمان و درجه حرارت محلول اسمزی، به جز در مورد امتیاز طعم، اثر معنی داری بر خصوصیات حسی خلال های سیب زمینی نداشت (p>0.05). بر طبق نتایج حاصل از بهینه سازی توسط روش سطح پاسخ می توان، غلظت 2 درصد، دمای 46 درجه سانتی گراد و زمان 173 دقیقه را برای پیش تیمار اسمزی به عنوان شرایط مطلوب معرفی کرد.
    کلیدواژگان: پیشتیمار اسمزی، خشککردن، فرآورده های سیبزمینی، روش سطح پاسخ
  • نرگس هادی گل، مریم فهیم دانش*، سپیده حسینی صفحات 369-380
    پوست انار یکی از منابع مهم ترکیبات زیست فعال بوده که توانایی بالایی در جایگزینی منبع زغال فعال مناسب برای جذب فلزات سنگین و رنگ بری در محیط مایع دارد. هدف از این تحقیق بررسی توانایی پوست انار در کاهش غلظت فلزات سنگین موجود در آب و روغن و همچنین ارزیابی عملکرد رنگ بری روغن آن است. در مرحله اول تحقیق شرایط جذب یون های فلزی در محیط آبی بهینه سازی گردید به این ترتیب که سه متغیر مستقل pH (X1)، زمان مجاورت ماده جاذب و فلزات (X2)  و غلظت ماده جاذب در محیط آبی (X3) بر درصد جذب یون های آهن و کروم (متغیرهای وابسته) بر اساس طرح باکس- بانکن بررسی شد. نتایج نشان داد که بیشترین جذب فلزات در شرایط 3/5=pH، در زمان 200 دقیقه و غلظت ماده جاذب 5/2 گرم در لیتر روی می دهد. در شرایط بهینه جذب فلزات سنگین سرب، جیوه و آرسنیک نیز مورد ارزیابی قرار گرفت و نتایج نشان داد که جاذب باعث کاهش 80 درصدی این یون ها می شود. در مرحله بعد توانایی رنگ بری و کاهش فلزات سنگین زغال فعال تولیدی در محیط روغن موردبررسی قرار گرفت. نتایج نشان داد این جاذب توانایی خوبی برای رنگ بری و پایداری اکسیداسیون روغن دارد. در رابطه با کاهش فلزات سنگین روغن نیز ماده جاذب تولیدشده از پوست انار عملکرد بهتری نسبت به خاک رنگ بر تجاری نشان داد.
    کلیدواژگان: پوست انار، جاذب، رنگبری، فلزات سنگین، روغن کنجد
  • فهیمه توریان*، مریم عزیزخانی صفحات 381-394
    تمایل به استفاده از نگهدارنده های طبیعی و جایگزین کردن آنها به جای نگهدارنده های شیمیایی سبب گردیده است مطالعات مختلفی در مورد ترکیبات طبیعی دارای خواص آنتی اکسیدانی و میکروبی مانند اسانس ها صورت پذیرد. در پژوهش حاضر اثرات کنسانتره آب نارنج و پوشش کیتوزان حاوی اسانس فلفل سیاه بر فساد شیمیایی فیله ماهی قزل آلای رنگین کمان نگهداری شده در یخچال مورد سنجش قرار گرفت. نمونه ها به 8 گروه تقسیم شدند و در دوره زمانی 12 روزه شاخص های pH، بازهای نیتروژنی فرار، تیوباربیتوریک اسید، میزان پراکسید، اسیدهای چرب آزاد و ارزیابی حسی مورد بررسی قرار گرفتند. همچنین نمونه ها از نظر فعالیت آنتی اکسیدانی به روش DPPH (دی فنیل پیکریل هیدرازیل) و RP (قدرت احیاکنندگی) ارزیابی گردیدند. با بررسی نتایج مشخص گردید که نمونه شاهد نسبت به سایر تیمارها به صورت معناداری افزایش روند شاخص های اکسایشی و حسی را نشان داد و در نمونه های پوشش داده شده نیز نمونه ماهی دارای کیتوزان، کنسانتره آب نارنج و اسانس فلفل سیاه کمترین میزان شاخص ها را نسبت به بقیه به خود اختصاص داد. از نظر مهار رادیکال DPPH، کنسانتره آب نارنج با بریکس39/1 و درصد مهار 9/66% و اسانس فلفل2% با درصد مهار 1/64% توانایی بیشتری داشته اند. در بررسی فساد اکسایشی و ارزیابی حسی در تمامی آزمون ها نمونه کیتوزان به همراه اسانس فلفل و کنسانتره آب نارنج با کسب امتیاز 2/7 از پانل ارزیابی حسی بهتر از سایر تیمارها ارزیابی شد. نتایج حاصله نشان دهنده تاثیر مثبت کنسانتره آب نارنج و پوشش کیتوزان دارای اسانس فلفل سیاه در مدت زمان نگهداری بر کیفیت فیله ماهی قزل آلای رنگین کمان می باشد.
    کلیدواژگان: ارزیابی حسی، فلفل سیاه، کیتوزان، ماهی قزلآلا، نارنج
|
  • Reza Farhoosh Pages 235-243
    Introduction
    Frying is one of the oldest and popular preparation techniques broadly used at home and food industry. High temperatures plus the presence of air as well as the water from the food being fried cause many destructive reactions. Therefore, thermal stability and performance of oil during frying is considered as one of the important criteria in the selection of frying oil. In this regard, balanced chemical composition, presents it as a valuable option for frying purposes. Studies show lipid autoxidation considered as the most important deteriorative reaction in the olive oil. This reaction leads to the formation of a series of primary and secondary oxidation products. Hydroperoxides are the primary oxidation products of lipid oxidation. Carbonyl value (CV) does measure secondary decomposition products are more stable than peroxides and the CV seems to be a good index of oxidative changes in lipids. Therefore, the determination of carbonyl compounds in frying oils is very important for evaluating the quality of frying fats and oils. Several studies have been carried out on the oxidative stability of edible oil during frying. Rancimat test has also been considered among the accelerated methods of lipid oxidation measurement due to ease of use and reproducibility. However, although estimate of oxidative stability of edible oil according to accelerated methods, is used widely but there is always worries about accordance the results of such tests with the results found under real frying conditions and Presence of food. Therefore, necessity of simultaneous study oxidative stability is essential in order to justify and extension of result together during heating and frying.
    Materials and methods
    Six refined olive oil samples of different brands in 1 lit glass bottles were purchased from local shops and were stored at 4 ºC for further analysis. Fatty acid methyl ester (FAME) standards, and all chemicals and solvents used in this study were of analytical reagent grade and supplied by Merck and Sigma Chemical Companies. The ratio between monounsaturated and polyunsaturated fatty acids (M/P) was determined by gas–liquid chromatography. The spectrophotometric method was used to determine the PV. The AV was determined according to the AOCS. The TT content was determined according to the colorimetric method. The TP content was determined spectrophotometrically using Folin–Ciocalteau’s reagent. The CV of the oils was measured using 2-propanol and 2,4-decadienal as solvent and standard, respectively. A Metrohm Rancimat model 743 (Herisau, Switzerland) was used to measure the OSI and IPCV of olive oil samples. Frying process was performed in bench- top deep- fryer at 180ºC. ANOVA and regression analyses were performed according to the MATLAB and Excel software. Significant differences between means were determined by Duncan’s multiple range tests.
    Results and discussion
    There was good correlation between the OSI and induction period (IPcv) at the temperature range studied with a high determination coefficient (R2>0.99) in the Rancimat test. Generally, the results of the present study showed that the Rancimat method at 110 ºC correlated well with stability under frying condition and this correlation decreased as temperature increased in the Rancimat test. These observations can be explained by the fact that steps or pathway of chemical reactions that take place at low and high temperatures are different. Thus, choosing the right levels of operational parameters in the Rancimat method can produce the least possible difference between frying and the OSI test.
    Keywords: Frying, olive oil, oxidative stability, Rancimat
  • Rezvan Pourahmad* Pages 245-255
    Introduction
    The aim of this study was to investigate the effect of immobilized glucose oxidase on magnetic chitosan nanoparticles on the content of organic acids (lactic acid and acetic acid), viability of probiotic bacteria and sensory properties of probiotic drinking yogurt.
    Materials and methods
    Different concentrations (0, 250, 500, 750 and 1000 mg/kg) of free and immobilized glucose oxidase were used in probiotic drinking yogurt. The samples were stored at 4˚C for three weeks.
    Results and discussion
    During storage, the content of acetic acid, counts of Lactobacillus acidophilus and Bifidobacterium lactis decreased and the content of lactic acid increased significantly (p<0.05). Addition of enzyme increased the viability of probiotic bacteria in test samples as compared to control sample (without enzyme). The viability of Bifidobacterium lactis in the samples containing high levels of enzyme (750 and 1000 mg/kg) was higher than other levels. The samples containing 500 mg/kg of free and immobilized enzyme had the highest count of Bifidobacterium lactis (7.88 log CFU/mL) and the amount of acetic acid in these samples (0.82 and 0.87 g/L, respectively) was more than other samples. There was no significant difference between the samples in regards to sensory properties. Therefore, addition of glucose oxidase immobilized on magnetic chitosan nanoparticles can decrease oxidative pressure and create suitable condition for the viability of probiotic bacteria in drinking yogurt and maintain overall acceptability. Moreover, it is economically feasible.
    Keywords: Chitosan, Immobilized glucose oxidase, Magnetic nanoparticles, Probiotic drinking yogurt1
  • Zohreh Didar Pages 257-266
    Introduction
    Metal oxide nanoparticles have unique physical and chemical properties. These components have shown antimicrobial effects against a wide range of microorganisms. In order to improve the physical properties of metal oxide nanoparticles, doping other elements with metal oxide nanoparticles is an effective way. Bacillus cereus is a gram-positive bacteria causing food-borne diseases. In this study, the antimicrobial effects of doped zinc oxide nanoparticles with manganese or iron on Bacillus cereus have been studied. To investigate the synergistic effects of the combined nanoparticles with two common biocides, including hydrogen peroxide and sodium hypochlorite, have been used.
    Materials and methods
    Co- precipitation method was used to prepare nanoparticles of manganese-zinc oxide and iron-zinc oxide. In this method, zinc sulfate and manganese sulfate were used to prepare manganese-zinc oxide  and iron sulfate and zinc sulfate are used for Zn- Fe doped nanoparticles. After preparing the sulfate solutions, the sulfate solutions were mixed and placed in an ultrasonic apparatus at a frequency of 57 kHz for 2 hours at 50ºC. Then, it was stirred at 80°C. A solution of NaOH was added until the pH of the solution reached 12. In these conditions, the mixing was done for 30 minutes. The solution was placed at ambient temperature for 18 hours. Then the centrifuge was performed to separate the sediment. Purification was done through washing with distilled water and ethanol. The precipitates were dried in the vacuum oven. In this way, the doped nanoparticles of manganese-zinc oxide and iron-zinc oxide were obtained. The Fourier transform infrared spectrum (FTIR) was carried out by the Perkin-Elmer apparatus of the Spectroma2 model, using a dry potassium bromide tablet at a frequency range of 4500-4000 cm-1. The X-ray diffraction was tested using the Phillips PW1820 from 2º to 80º. Structure of produced nanoparticles was assessed by the HITACHI electron microscope, the H-7500 model, by placing a drop of nanoparticles dissolved in methanol on a special lining with carbon coating and air drying, and performing microscopic images using an electron microscope in 100kv. The bacteria used in this study included Bacillus cereus (PTCC 1665) was purchased from the Iranian Scientific and Industrial Research Center and was transferred to the BHI medium in sterile condition and incubated for 32 hours at a temperature of 32°C. Microbial cells were isolated by centrifugation at 4000 rpm. McFarland's method was used for determining the bacterial population. Dilution was carried out to reach a population of about 106 CFU/ml. Agar disc diffusion method was used for assessing the antimicrobial effect of the doped nanoparticles alone or in combination with tested biocides (hydrogen peroxide, sodium hypochlorite). At first, 106 CFU/ml of Bacillus cereus were inoculated on the surface of Blood Agar. Then, 5, 10, 20, 30, 50, 100 and 200 mg/L of each of the nanoparticles were placed on the surface of the culture medium and then the plates was incubated at 37°C for 24 hours. Inhibition zone was considered as antibacterial activity. In order to investigate synergistic effects, inhibitory fraction index test was calculated. All experiments were performed in three replications. Statistical analyzes were performed using STATISTICA software.
    Results and discussion
    Results obtained from X-ray and FTIR analysis of doped nanoparticles confirmed that co- precipitation is a suitable method for producing doped nanoparticles of zinc oxide. TEM analysis of produced nanoparticles also affirm formation of doped nanoparticles of zinc oxide with manganese and iron. The results of antimicrobial tests showed that Mn-Zn oxide nanoparticles have more antimicrobial effects on Bacillus cereus than zinc oxide (32mm inhibition zone) whereas Fe- Zn oxide nanoparticles cause inhibition zone about 12 mm. In addition, both doped nanoparticles have more antimicrobial effects than zinc oxide nanoparticles alone, resulted in doping process improves antimicrobial properties of zinc oxide. The synergistic effects of synthetic nanoparticles in the combination of two common antimicrobial agents, including hydrogen peroxide and sodium hypochlorite, have been identified. Both nanoparticles show synergistic effects in combination with two tested biocides (especially in high concentrations). A mixture of two biocides with nanoparticles increases their antimicrobial properties. Manganese-zinc oxide nanoparticles with hydrogen peroxide and sodium hypochlorite showed a partial synergistic effect at low concentrations (5 + 20) and a complete synergistic effect at higher concentrations. In the case of iron-zinc oxide, combination of this nanoparticle with hydrogen peroxide and sodium hypochlorite, has complete synergistic effects at high concentration (100 + 200) and at other conditions, shows partial synergistic effects.
    Keywords: Doped nanoparticles, Zinc oxide, synergistic, Bacillus cereus
  • Mirkhalil Pirozifard Pages 267-279
    Introduction
     Raw sugar beet juice (RSBJ) is an intermediate of sugar beet processing obtaining by diffusion process. The RSBJ contains approximately 85% water, 13% sucrose, and 2% non-sugar compounds (impurities) and its purity ranges from 85 to 88%. Due to the low purity, the RSBJ should be subjected to purification process. The conventional purification occurs in a complex multistage process including pre-liming, main liming, first carbonation, and second carbonation. In liming step, lime milk (Ca(OH)2) is added to destabilize and precipitate the non-sugar compounds. Then the CO2 gas is added to precipitate the lime (as calcium carbonate). Although the application of lime is very well known but some impurities, including phenolic compounds, saponins, proteins and lipids pass through purification processing into the white sugar and cause serious difficulties. Due to the variety of compounds (dissolved or suspended) present in RSBJ and this fact that different processes may remove different types of compounds, various fining agents are required to clarification of raw juices. Bentonite, silica sol, gelatin and activated carbon are four types of natural adsorbents, which have been used in many applications, in different fields and processes, including the food industry. Differences in the nature of ionic charges of juice compounds and the fining agents induce neutralization, and flocculation and result in the removal of them from the juice. Therefore, the purpose of this study was to investigate the efficiency of bentonite, silica sol, gelatin and activated carbon in the removal of impurities (protein, saponin and phenolic compounds) causing floc in acidic beverage and improving the purification indexes of RSBJ (turbidity, color, ash and purity). Floc refers to the cloudy and turbid precipitate that forms in some sugar-sweetened carbonated soft drinks after standing for several days. While flocs are harmless, they are a visible defect and consumers don’t accept the soft drink product for aesthetic reasons. Currently, most researchers assume that saponins are primarily responsible for floc formation. However, there are some studies indicating that protein, phenolic compounds and lipids also play a role in floc formation.
    Materials and methods
    The RSBJ was regularly obtained from the sugar factory of Piranshahr, Iran. The RSBJ was sampled at the point just before the purification step and immediately transferred to the lab. Fining agents used for clarification including bentonite (Na–Ca Bentonite ERBSLÖH, Geisenheim, Germany), silica sol 15% (Baykisol 15%), Gelatin (type-A; 100 bloom, Erbigel, Germany) and activated carbon (CS-2000, Gostar Ghoumes CO. Iran) was provided by Azar kam Co. Urmia. Iran. For each experiment, 200 ml of the raw juice was subjected to various refining treatments. The RSBJ were refined at 75 °C for 100 min by fining agents. Fining agents were added to beet juice samples according to the preliminary experiments. After the completion of the clarifying process, juice samples were passed through a microfilter (45 µm) to removing formed floc. In order to compare the mentioned treatments (bentonite, silica sol, gelatin and activated carbon) with the conventional method, the RSBJ was also treated with lime-carbon dioxide in four stages (pre-liming (15 minutes at 85 ° C), main liming (15 min at 88 ° C), first carbonation (up to pH 11, 90 ° C) and second carbonation (up to pH 9, 92 ° C)). After applying the treatments, purity and ash content (by conductimetry method) was measured as the main purification indexes for assessing the quality of the juice samples. The total protein (by dye-binding method), total phenolic compound (by Folin-Ciocalteu reagent) and total saponin content (by vanillin-sulfuric acid method) was also determined as the compounds have a key role in formation of acid beverage floc.
    Results and discussion
    In this study, four refining agents of bentonite, silica sol, gelatin and activated carbon were used to improve the purification indexes of RSBJ and to remove non-sugar impurities causing floc in acidic beverage (such as carbonated beverages). Based on the ash and purity, it was showed that the applied adsorbents (bentonite, silica, gelatin and active charcoal) significantly improved the purification indexes of RSBJ. The results also showed that the ability of bentonite as a negative charged adsorbent was considerably higher than silica-sol in removing impurities (protein, saponin and phenolic compounds) causing floc, and improving the purification indexes (turbidity, color, ash and purity). So, the bentonite treatment reduced protein, phenolic compounds and saponin content of juice by 68, 61 and 40 %, respectively. The combination of gelatin and activated carbon as supplemental clarifiers with bentonite and silica also improved the parameters measured. In general, Bentonite-Activated carbon treatment had the best results, resulting in a reduction of 73, 87 and 85 % in protein, phenolic compounds and saponin, respectively. In this study, mentioned treatments were also compared with conventional treatment (lime-carbon dioxide) and it was observed that new treatments can be a good choice to combine or replace with conventional treatment.
    Keywords: Sugar beet juice, Chemical purification, Bentonite, Silica sol, Gelatin, Activated carbon
  • Mohammad Fazel Pages 281-296
    Introduction
    The fruit, with the scientific name of Cydonia oblonga comes from apple family, has a dry and fluffy flesh that, due to high vitamin C, Potassium and fiber has commercial and nutritional value. However, this fruit is as corruptible as other fruits and destructive microbial, chemical and mechanical factors that reduce its effective longevity. Enzymatic browning is a major problem for reducing the shelf life of freshly chopped fruits and vegetables. This reaction often occurs due to the activity of polyphenol oxidase (PPO) and peroxidase (POD) enzymes. Blanching is used to deactivate the relevant enzymes. Blanching is done before such processes as drying, canning, and freezing and somewhat determines the quality of the product. Sulfites are multi-functional compounds that inhibit enzymatic and non-enzymatic browning. Dehydration is one of the oldest techniques for keeping food products. Osmotic dehydration process has been emphasized in recent years due to the negative effects of conventional drying procedures, this process is done to partially remove the water from the plant tissue by immersion in a salt or salt solution. Chitosan is non-toxic, biodegradable substance that can be used as an edible coating to maintain the quality and increase the life after the fruits and vegetables harvest. This protective performance improves by adding antimicrobial, antioxidant. The lemongrass extract was added to the chitosan coating as antimicrobial. The purpose of this study is to investigate the effect of chitosan coating containing lemongrass extract on the shelf life of dehydrated quince fruit slices.
    Materials and methods
    Metabisulfite was used in order to prevent the browning reactions of slices prepared from blanching, water vapor and chemical solution of sodium. Then, quince slices are dehydrated with osmotic solutions of sorbitol, sucrose by immersion with chitosan containing (0, 0/5, 1 and 2 % lemongrass extract) coated and kept in sterile plates at refrigeration temperature (4±1˚C) for 4 weeks. The experiment was carried out in factorial method based on a completely randomized design with three iterations. Variables include the type of osmotic solution (sucrose, sorbitol) and coating treatments (chitosan coating containing 0, 0/5, 1 and 2% lemongrass extract). The studied characteristics included weight loss (%), acidity, pH, ascorbic acid concentration, total phenol, inhibitory activity of free radical (RSA), color properties (components L*, a*, b*, BI) of tissue that was investigated in the first, second, third and fourth week.Results &
    discussion
    Fruits coated with chitosan containing 2% lemongrass extract had less weight loss changes than other treatments. This can be due to the role of the extract in preventing decay, its antimicrobial properties and the formation of the semipermeable membrane by coating, which prevents weight loss. Edible coatings containing extract, by changing the internal atmosphere and reducing the respiration rate of the fruit, help to maintain better organic acids .Lemongrasses extract causes the delay in the consumption of organic acids in metabolic reactions, including respiration, due to its antioxidant properties. It seems increasing the pH of the fruit is the result of biochemical changes in the fruit during storage time, such as the decomposition of organic acids into sugars and participating the respiratory cycle in which the coating of chitosan containing extract can reduce the breakdown of organic acids by reducing respiration rate. The decrease in the drop of Vitamin C and phenolic compounds of the coated sample is due to oxygen permeation reduction and the creation of adapted atmosphere by coating. The high level of antioxidant activity of lemongrass extract is because of high phenolic compounds of which the highest amount was observed in treatment coated with chitosan containing 2% lemongrass extract. By increasing the concentration of the extract, its phenolic compounds increases which preserve more vitamin C and phenolic compounds and consequently antioxidant properties. Free radical inhibition activity was preserved due to better preservation of phenolic compounds, ascorbic acid and increasing the antioxidant capacity of fruit by chitosan coating containing lemongrass extract. The product brightness decreases during storage. Before the hot-water blanching coating process, sodium metabisulfite and osmotic dehydration have inactivated browning enzymes. Therefore, in quince coated with chitosan, the amount of color changes was not tangible due to the less respiration and as a result, less enzymatic activity of fruit. Coating containing lemongrass extract has created due to the color of coating extract with the green-tinted color. The increase in the extract concentration reduces the redness and increases the greenness of fruit, which is because of the extract color and as the effect increases, the concentration increases. By decreasing the brightness, increasing the greenness and yellowness during storage time and the browning increased. In quince coated with chitosan, the amount of softening wasn’t tangible due to less respiration and as a result, less enzymatic activity of fruit. As the concentration of lemongrass increases the stiffness of the tissue is reduced due to the effect of lemongrass on the fruit tissue cells that cause structural changes. Based on the results, the edible coating containing 2% lemongrass extract is suggested as the best formulation.
    Keywords: Lemongrass Extract, Chitosan, Quince fruit slices, Osmotic Dehydration, Edible coatings
  • Mohammad Ziyayefar Pages 297-307
    Introduction
    Tomato consumption is recommended due to its brilliant color, amazing taste, high antioxidants and vitamins content. Pectin methylesterase (PME) is known as a pasteurization index in tomato juice. This enzyme plays important roles in cloud stability, color, viscosity and organoleptic properties of the juice. PME induces the cloud loss in the juice due to the formation of the insoluble calcium pectate; its inactivation is therefore needed to maintain the juice stability. Degradation of ascorbic acid (AA) in the juice is considered as a major challenge during thermal food processing procedures. Furthermore, during its degradation non enzymatic browning occurs, affecting the taste and color. Novel juice processing methods such as infrared (IR) heating and pulsed electric field (PEF) reduce the adverse effects of the conventional thermal method. Quick IR heating produces a juice having higher nutritional value and better quality. During PEF processing, the juice is subjected to high voltage electric pulses for a few microseconds to inactivate target microorganisms and enzymes. Considering the protein structure of the PME, PEF processing at a higher temperature can be effective in this enzyme inactivation. A quick pre-heating of the juice using IR heating was therefore applied in this study. Furthermore, the ohmic heating, occurring during PEF treatment, was not prevented. The synergistic effect of thermal treatment and a non-thermal one (continuous PEF system) on some physicochemical properties of tomato juice were investigated.
    Materials and methods
    Tomato juice, with an initial temperature of 30℃, was firstly preheated using a continuous IR heating system. During the IR treatment, a temperature controller was applied to set the outlet temperature of the juice to 40, 45 and 50℃. The preheated juice was then passed through a continuous PEF system. The process chamber of the PEF system consists of two parallel stainless steel electrodes with 0.55 mm distance. The length and width of the exposed electrode surface were 10 mm and 0.5 mm, respectively. A square-wave bipolar pulse with a width of 1 ms was selected to perform the treatment within the range of 22.73 to 36.36 kV/cm at 32 Hz. The outlet temperature of the juice was recorded using a data acquisition system during 3.52 s PEF treatment. The treated juice was cooled in an ice-water bath to minimize the effect of cooling period on PME inactivation. AA content, PME activity, cloud value and color of the juice were measured using iodine titration, Kimball, spectroscopy and image processing, respectively.
    Results and discussion
    Results showed that higher PME inactivation was observed in the juices treated at higher IR pre-heating temperature in combination to higher PEF intensity, resulting in higher cloud stability of the juice. While preheating of the juice decreased the AA content, PEF treatment has no significant effect reflecting the heat sensitivity of this vitamin. Furthermore, color aspects of the juice were more affected by heating treatment in comparison to the PEF processing. Browning index (BI) increased as the AA content decreased. By measuring the total color difference (TCD) it was shown that the PEF had no impact on color properties of the juice. Therefore, the synergistic effect between the IR heating and PEF treatment was also effective in producing the juice having the high nutritional value and better appearance.
    Keywords: Infrared, Pulsed electric field, Tomato juice, Ascorbic acid, Pectin methylesterase, Color aspects
  • Mehdi Khojastehpour Pages 309-322
    Introduction
    One of the new methods for improving the mechanical properties of bioplastics is the production of blending based bioplastics. Recent studies show that proteins, in combination with starch, form a strong network of hydrogen bonds and intermolecular interactions that resulted stable 3-D materials. The big problem in the commercialization of blending based bioplastics is the lack of industrial machinery for the continuous production of bioplastics with the direct use of biopolymers. Industrial production of bioplastics is accompanied by increasing heat along with applying the pressure. It is necessary to know the kinetics of thermal degradation of bioplastics to study thermal behavior at different temperatures in order to design bioplastics processing devices and molding machines, software modeling of processes, mass and energy equilibrium, and optimizing energy consumption in the production process along with improving the thermal properties of the bioplastics.
    Materials and methods
    In this study, the dynamics thermal decomposition of bioplastics prepared from a mixture of potato whole flour-gelatin and glycerol with a control sample consisting of potato whole flour and glycerol was investigated and compared. The gelatin was extracted from chicken feet using chemical methods. In this research, two isoconversional models including Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models were considered. Using each of these models, thermal decomposition kinetic parameters were calculated for bioplastic samples.
    Result and discussion
    The results showed that the maximum activation energy of the mixed bioplastics determined 162 and 150 kJ/mol by FWO method at the conversion ratio of 0.9 and 0.5 respectively, while it was 217 kJ/mol at the ratio of 0.6 for control bioplastics. The amounts of kinetic parameters calculated in this study, were able to determine the thermal behavior at different temperatures and the thermal decomposition process. Also, it can help to redesign and optimize the methods of molding and shaping of potato-gelatin based bioplastics by the use of existing machinery in the industry.
    Keywords: Activation energy, bioplastic, gelatin, potato, thermal decomposition kinetics
  • Mohammadreza Edalatian Pages 323-339
    Introduction
    Carrot products such as carrot juice and fermented carrot products possess high nutritional value and they are considered as a major source of β-carotene. Carotenoids because of containing conjugated double bonds, have antioxidant properties and provide the natural yellow, orange and red colors in fruits and vegetables. Due to the outbreak of some problems such as lactose-intolerance and high blood cholesterol especially in dairy products’ consumption, great attention has been drawn toward fermented vegetable products. Lactic acid bacteria (LAB) including important genera: leuconostocs, lactobacilli, streptococci and pediococci are wide-spread and have been divided according to morphological features and fermentation pathway, which utilize glucose. Current knowledge regarding involved microorganisms in vegetable fermentation is still dependent on biochemical and classical data. Nowadays, application of molecular methods in the field of microbial identification has been provided better understanding from fermented foods ecology. Since local starter cultures are considered as precious genetic resources in each country and also they play an important role in production and creation of organoleptic characteristics in fermented products, therefore, the objective of present study was the isolation and identification of lactic flora from fermented carrot with the help of conventional (biochemical) and molecular methods and determination of phylogenetic relationships.
    Materials and methods
    Following the production of fermented carrot samples, they were packed in plastic container and stored at ambient temperatures (25-27°C). In the next step, total LAB count was performed according to Iranian standard of 5484. Isolation and selection of LAB was done during 32 days with the intervals of 0, 4, 8, 16, 24 and 32. For initial identification of LAB, isolated were subjected to gram staining and catalase tests. Also biochemical tests including growth at 15 and 45C, at NaCl 6.5% and 18%, pH=4.4 and 9.6, were done in order to identify   and classify at genus level. Carbohydrate fermentation profiles were obtained for isolates with the aid of 10 sugars. Molecular identification was done with DNA extraction followed by amplification of 16S gene with universal primers (27 F and 1492 R). For sequencing of resulted PCR-products, they were sent to Macrogen Company, South Korea. Phylogenetic tree was plotted with Clustal Omega and Fig. Tree soft wares.
    Results and discussion
    In the first step, 144 gram positive, catalase negative isolates were screened and selected as presumptive LAB according to gram staining and catalase test and morphological characteristics. Among them, 48 representative isolates were chosen and identified up to genus level according to biochemical tests. Five distinct genera were identified as Pediococci (4.08%), homofermentative lactobacilli (34.69%), hetero fermentative lactobacilli (36.74%), Leuoconostocs (20.41%) and enterococci (4.08%). Carbohydrate fermentation profiles revealed Lactobacilli constitute the highest percent among other genera and also some species like Lb. kimchi and Lb. parakefiri were detected. Growth of lactic acid bacteria experienced increasing trend up to day-16 but thereafter showed decline trend until the end of storage time (day-32). 26 out of 48 isolates were subjected to molecular analysis. Results of sequencing revealed following species: Lb.plantarum (9), Lb. brevis (8), Leu. mesenteroides (4), Lb. casei (1), Lb. paracasei (1), and Lb, pantheris (1). Changes and variation of lactic flora during fermentation stages revealed that at initial stages of fermentation  (0- day-8) Leuconostocs sp. were predominant species but disappeared then. In the next stages of fermentation Leuconostocs sp. were replaced by homo-fermentative strains such as Lb. plantarum which was present from the first day up to day-24 but constituted the majority of species on day-16. In the final stage, Lb. brevis dominated the others due to better survival and resistance of this bacterium at the increased acidity level. Phylogenetic tree results revealed three clusters including cluster I (composed of three sub-clusters), cluster II (three sub-clusters) and cluster III (two sub-clusters). Cluster I included two genera: Leuconostocs sp. (mesenteroides) and Lactobacillus (pantheris, casei and paracasei). Cluster II included Lb. brevis and finally cluster III composed of Lb. plantarum.
    Keywords: Biodiversity, Lactic acid Bacteria, Carrot, Fermentation, Phylogeny
  • Mohsen Azadbakht Pages 341-353
    Introduction
    The study of relationship between physical properties such as mass and volume and other physical properties, such as geometric dimensions, has been the subject of numerous studies by researchers. The fruit size, shape and mass are important in sorting and measuring fruits, and it determines that the fruits can be put in boxes of transport or plastic bags by a specific size. Damage to the fruit may be due to various causes, including Impact, pressure and vibration, all of which cause physical damage at moment or at storage time, the amount of damages depends on location of impact, the size and volume. Also, the volume and physical properties of agricultural products are very important for storage. On the other hand, cell damage and forces involved in fruits reason bruising in fruits, which can be controlled by physical properties. Quality assessment is usually carried out using a combination of destructive and non-destructive methods, generally done by the product manufacturers or the first purchasers, and includes the separation of materials based on specific size and weight. Among non-destructive methods used, the use of CT and X-rays, which allow a person to examine bruises at different times in the fruit, is increasing. Due to the fact that mass and volume of fruits for storage, transportation, packaging and etc are of great importance, in this research, the relationship between pear fruit volume and mass with bruise percentage during the storage period was studied using non-destructive CT scan tests due to dynamic loads.
    Materials and methods
    Firstly, the pendulum and the required masses were made in a workshop. The fruits were placed in the desired position and then the device arm was raised to the desired angle (90°), and in the controlled state of the arm impact the pear. The pendulum had a 200 g and three different attachment masses of 100, 150, and 200 g for knocking. It should be noted that air resistance and friction were neglected through this procedure. In this research, via CT scan, the relationship between mass and volume of pears (Before and after the impact) due impact loading and storage times with bruise was investigated. Before loading and storing, 50 pears were examined using Scan CT and 27 pears with zero bruise percentage were selected, the next chosen pears were subjected to impact loading with a pendulum with three weight of 300, 350 and 400 g and 5, 10 and 15 days storage was used to investigate the effect of impact on pears. Then, after impact and storing, with the use of CT scan in each period of storage, the rate of pear bruise was calculated.
    Results and Discussion
    The pears volume before impact with the bruise percentage for all three weights had a negative and non-significant correlation and the decrease pear mass percentage with the bruise percentage for all three weights has a positive correlation and pears mass before impact with the bruise percentage for all three weights had a positive and non-significant correlation. Any decrease in pear mass percentage had a positive correlation with caries percentage for all three weights. The correlation test showed that with the increase in pear volume, the bruise percentage was decreased and a direct correlation was found between the decreasing percentage volume and the bruise percentage. –also The effect of 5-day storage duration was found considerable on the bruise percentage subject to the exertion of 350 g and higher impact  rates
    Keywords: Pear, CT scan, Non-destructive, bruise, volume
  • Seyed Hamidreza Ziaolhagh Pages 355-367
    Introduction
    Potato is the fourth most important agricultural product after rice, wheat, and corn. Potato produces more dry matter, protein, and minerals per unit area in comparison with other crops. Many of the ingredients in potato are important, due to their beneficial effects on health. Hence, this product is very suitable for human consumption. Osmotic dehydration is used to remove a portion of water from foods such as fruits and vegetables, by immersion in high osmotic solutions such as sugars and salts.  Osmotic dehydration is a relatively simple and economical process that improves the texture and rehydration properties of the products and prevents enzymatic browning by preventing the activity of polyphenol oxidases. In this process, the acid is removed and the sugar is absorbed, thus the composition of the fruits is changed and the taste and total acceptance of the product are improved. Osmotic dehydrating method has been used for drying various products such as carrots, mangoes, pineapples, strawberries, bananas, apples, apricots, and many other fruits. In this research, the effects of osmotic pre-treatment on qualitative and sensory properties of dried potatoes were investigated.
    Materials and methods
    In this study, Agria cv. potato samples were used and after washing, were completely peeled and cut into pieces of 3.5 × 0.5 × 0.5 cm. The treatments used in this study included osmotic solution concentration (at 0, 10 and 20% sodium chloride levels), osmotic solution temperature (30, 45 and 60°C), and immersion time in osmotic solution (at three levels 60, 240 and 720 minutes). The proportion of potato sticks to osmotic solution in all experiments was 1:6. After applying osmotic pre-treatment, samples were dried in an oven with a temperature of 60°C and a flow rate of 1.5 m/s to reach a moisture content of 8-10%. The moisture content, rehydration capacity, shrinkage, browning, color indices, and sensory properties (taste, color, shape, strength, and total acceptance) of potato samples were evaluated after the drying process and the response surface methodology (RSM) based on central composite design (CCD) were used to determine the optimal conditions for osmotic pre-treatment.
    Results and discussion
    The results of statistical analysis of the data showed that osmotic time and osmotic solution concentration had a significant effect on moisture content of potato slices. By increasing the time and decreasing the concentration of osmotic solution, moisture content of dried potato samples increased. The immersion time and osmotic solution temperature did not have any significant effect on the rehydration of potato slices, but the effect of osmotic solution’s concentration was statistically significant. By increasing the concentration of osmotic solution, the rehydration rate of potato samples decreased. The results showed that the interaction of temperature and concentration of osmotic solution had a significant effect on the degree of shrinkage of potato slices. Osmotic time and osmotic solution concentration had statistically significant effects on the browning index of potato slices, in a way that by increasing the concentration of osmotic solution, the browning index of potato samples decreased initially and then increased. The results of statistical analysis of the color indices showed that the osmotic solution temperature had a significant effect on the brightness (L*) of the potato slices, while the concentration of osmotic solution significantly affected their yellowness (b*) and the temperature and concentration of osmotic solution had a significant effect on the redness (a*) of the potato slices. By increasing the concentration of osmotic solution, the overall change in the color (E) of potato samples at high temperatures of osmotic solution first increased and then decreased. Sensory evaluation results showed that concentration, time, and temperature of osmotic solution had no significant effect on the sensory properties of potato sticks, except for taste. By increasing the temperature and time of immersion in osmotic solution, the taste scores of the samples increased.  According to the results of optimization by the surface response method, the concentration of 2%, temperature of 46° C and dipping time of 173 min was introduced as favorable conditions.
    Keywords: air drying, dried foods, osmotic dehydration, potato products, Response surface methodology
  • Maryam Fahim Danesh Pages 369-380
    Introduction
    Pomegranate peel is an important source of bioactive compounds which have high potential of alternative source of activated carbon for bleaching and the removal of heavy metal from liquid media. The present study was undertaken to evaluate the feasibility of pomegranate peel carbon for the removal of heavy metal from oil and aqueous solution and then to investigate its activity in the bleaching of sesame oil.
    Materials and methods
    Response surface methodology and Box-Behnken design were applied to study and optimize the adsorption condition to remove metal ions on prepared pomegranate peel adsorbent. For this purpose, the effects of three independent variable pH(X1), contact time (X2) and adsorbent dose (X3) on metal ions concentration (dependent variable) were studied using a three-level three-factor Box–Behnken design. In addition, different types of adsorbents (pomegranate peel carbon and activated earth) were tested for adsorption of pigment, peroxides and heavy metals of sesame oil.
    Results and discussion
    Results showed that optimum condition required for maximum adsorption were found to pH= 5.3, equilibrium time 200 min and adsorbent concentration 2.5 g/L. Under the optimal conditions the removal of heavy metals i.e. Fe, Cr, Pb, as and Hg from aqueous solution by activated carbon developed from pomegranate peel are more than 80%. Results of sesame oil bleaching with pomegranate peel carbon showed good bleaching efficiency and oxidative stability. Furthermore, pomegranate peel carbon comparing with bleaching earth showed better ability to decrease heavy metal content of oil.
    Keywords: Adsorbent, Heavy metals, Pomegranate peel, Sesame oil
  • Fahimeh Tourian Pages 381-394
    Introduction
    Nowadays, consumers are applicant to usage of natural replacements causing to side effects of synthetic preservatives such as carcinogenicity and teratogenicity. The tendency to use natural preservatives and replacing them with chemical preservatives has led to various studies of natural compounds with antioxidant properties such as essential oils. Considering the environmental problems raised from current plastic packaging, edible and biodegradable coating could be developed and also be effective in controlling the chemical and microbial properties of food; especially if their effect be strengthened by adding natural antioxidant and antimicrobial agents like herbal essential oils. Various herbal compounds such as black pepper essential oils with antioxidant properties can be effective in combining with natural biodegradable coatings such as chitosan in oxidation control and enhance the effects or prevent or delay the chemical spoil. Safety and shelf-life of foods can be improved by using this technologies such as using natural preservatives. Adding essential oil, as a suitable source of antioxidant, for improvement the quality of the fish is the main purpose. Many fruits, especially orange, are rich in polyphenols. These materials are the most commonly existing phytochemicals in most fruits. Orange juice concentrate can be a good source of antioxidant and can be employed as a preservative in food products. Omega-3 fatty acid is used in daily healthy diet and plays an important role in prevention of disease. Being a considerably main source of Omega-3 fatty acid groups, fish preservation against oil oxidation and any other similar causatives seems quite necessary. In the present study, the effects of orange juice concentrate and chitosan coating enriched with black pepper essential oil on the chemical degradation of rainbow trout fillet stored in a refrigerator investigated.
    Materials and methods
    The chemical composition of black pepper essential oils were determined using a gas chromatography equipped with mass spectroscopy (GC/MS). GC-MS analysis of the essential oil was performed using Agilent-Technologies 6890N Network gas chromatographic (GC) system, equipped with Agilent Technologies 5975 inert XL Mass selective detector and Agilent-Technologies 7683 B series auto injector (Agilent-Technologies, Little Falls, CA, USA). Samples were stored at 4 ± 1 C° up to 12 days and evaluated periodically ( on days 0, 4, 8 and 12) for chemical and sensory characteristics. The samples were divided into 8 groups and assessed for PH-values, total volatile nitrogen (TVN), thiobarbituric acid (TBA), peroxide value (PV), free fatty acids (FFA) and sensory evaluation .The samples were also evaluated for antioxidant activity by measuring their scavenging abilities to DPPH radical (2,2 diphenyl-1-picril hydrazyl) and RP (Reducing power). Statistical analysis was performed using SPSS 20 software.Results &
    Discussion
    Results showed that More than 21 compounds were identified in oil, representing 97.75% of the total oil. The major constituents of essential oils obtained from the black pepper were β-caryophyllene (25.56%), Limonene (15.19%), Sabinene(12.2) , α-copaene(8.5) and beta –bisabolene (7.81) respectively. Results revealed that in comparison to the other treatments the control showed a significant increase in the trend of oxidative and sensory indexes and In the coated samples, the sample of fish coated with orange juice concentrate ,chitosan, and black pepper essential oil was the least amount of indexes than the rest (p<0/05) and showed lower indexes during the storage time .The radical scavenging DPPH, orange juice concentrate with a Brix 1/39 (66/9 %)and pepper essential oil 2% (64/1%) have more ability and had a greater antioxidant activity. In investigating corruption oxidation and sensory evaluation in all samples,chitosan coating with pepper essential oil and orange juice concentrate was higher(score:7/2) than other treatments and there were significant differences between treatment and control (p<0/05). Final peroxide value (meq O2/Kg oil) and tiobarbituric acid (m gr/kg oil MD) number using chitosan coating with pepper essential oil and orange juice concentrate in sample was 0.14 and 0.015, respectively. This significant deference was also observed when comparing to control sample (p<0.05)Minimum oxidative changes were observed in samples treated with orange juice concentrate,chitosan, and black pepper essential oil and had the best conditions in reduction of oxidative rancidity. The results obtained in this study showed that the chitosan coating enriched with black pepper essential oil with orange juice concentrate has a good potential to being employed as an active packaging to preserve food products. Overall, this study demonstrated that using concentrated juice incorporated with chitosan coating with pepper essential oil has a good effect on the quality of rainbow trout fillets and can keep on the sensorial attributes acceptably during 12 days storage time and present a good potential for their application in the food industry.
    Keywords: orange, black pepper, chitosan, Oncorhynchus mykiss, sensory properties