نشریه فرآوری و نگهداری مواد غذایی
سال هفتم شماره 1 (پیاپی 17، بهار و تابستان 1394)

The traditional methods used to produce concentrated yoghurt are Tuluq and Torba bags. In this study, nutrients losses during the production of traditional concentrated Tuluq and Torba yoghurts were evaluated. Firstly control yoghurt was produced by standard method. Then, concentration processing was carried out in Tuluq and Torba bags at 4 ℃. Finally, losses content were evaluated based on chemical compounds with standard methods and mineral with flame photometer, atomic absorption and micro kjeldahl apparatus. The results showed that in Tuluq and Torba yoghurts the losses were solid content (41.04, 81.04%), protein (5.05, 10.64%), fat (0.32, 3.85%), lactose (68.19, 144.78%), ash (131.57, 230.40%) and salt (35.6, 73.80%), respectively. Among the essential mineral, potassium (72.52%) and sodium (70.25%) had the highest losses amount but calcium (17.83%) had the lowest losses. Since Tuluq yoghurt has high content of pH, protein, fat, and ash whilst include low content of lactose and salt, therefore manufacturing of Tuluq yoghurt is proposed as a valuable dairy product with high nutritional quality and low losses.

Thermal treatments were effective on rheological and textural properties of hydrocolloid solution and can change functional and color properties. In this study, under optimum conditions, Balangu seed gum were extracted and dried. Then, concentration of 0.2% (w/w) of gum were prepared for determine rheological and color Characteristics and concentrations of 3, 4% (w/w) for of textural properties, and then subjected to freezing treatments (-18 and -25°C for 24 h). Apparent viscosity and flow behavior were measured at 25°C by Brookfield rotational viscometer and fitted with power law, casson and bingham models. Compression tests were conducted by using a texture analyzer and characteristics like hardness, consistency and adhesiveness were measured. Power law model well described non-newtonian pseudo plastic behavior of the highest hardness; value of Balangu seed gum gels (3%) was observed in sample treated at -25ºC for 24 h, 8.5gr. Therefore, Balangu seed gums can be suggested as a textural and rheological modifier in formulation of foods exposed to freezing treatments.

It is well known that lipid peroxidation is a major course of quality changes which affect the flavor, texture and appearance in foods. In addition, it has been recognized that oxidative stress plays a significant role in a number of age specific diseases. The factors involved in these diseases are the lipid peroxides and low molecular weight compounds produced during the late stage of the oxidative reaction. Hence, to prevent foods from undergoing deterioration and to provide protection against various diseases, it is important to inhibit the peroxidation of lipids and formation of free radicals occurring in the living body and food stuffs. Due to safety concerns and health aspects over the use of synthetic antioxidants, the natural antioxidant compounds are considered by researchers. Protein hydrolysates are the source of natural antioxidant. The need for natural antioxidants in food and pharmaceutical resulted in extensive scientific research, in recent decades. antioxidant activity of whey protein hydrolysates on oxidative stability of soybean oil were studied and compared with synthetic antioxidants, by measuring their peroxide and thiobarbituric acid values during accelerated storage. Protein hydrolysate and synthetic antioxidant at four different concentrations (100, 300, 500 and 700 ppm) were added to soybean oil. Protein hydrolysate and antioxidant BHT were retarded oil oxidationat 70°c. The peroxide and thiobarbitoric acid values of control samples were 85.08 (meq peroxide/ kg oil) and 0.22 (mg malon aldehyde/kg oil) after fifteen days storage while this values were 45.05 and 0.082 for oil sample contain 700 ppm BHT and for oil sample contain 700 ppm protein hydrolysate were 49.75 and 0.094, respectively. That the antioxidant peptides can be used as anatural antioxidant in food formulations.

In recent years, application of biodegradable films for coating has been taken into account for better preservation and increase the visual appearance of food products has been. The purpose of this study was to investigate the effects of nano-clay and -Carrageenan on the mechanical properties, permeability to water vapor and oxygen of gelatin cold water fish films. In this study, films of cold water fish gelatin and -Carrageenan (0.5%) and nano clay (zero, 0.5, 0.75 and 1%) were prepared by using casting. Mechanical tests of bio-nanocomposite films increased tensile strength and percent elongation decreases due to the increased concentration of nanoparticles. Permeability to water vapor and oxygen, with increasing nanoparticles significantly reduced (P<0.05). According to investigations, nano-clay had the ability to improve the basic properties of gelatin films of cold water fish and so, can be used as edible coatings for food packaging and agricultural products.

Economic benefits of lactic acid bacteria have encouraged microbiologist to identify local bacteria for industrial use. In this study Lactobacillus spp. were isolated from raw milk that had been collected from two domestic milk collection centers, Sarab and Ardebil, Iran. These isolates were characterized by phenotypic methods and their ability to reduce pH as a technological property was determined. Six out of 14 isolates were identified as Lactobacillus spp. based on biochemical and physiological characterization. The following species were identified: Lactobacillus plantarum, L. acidophilus, L. curvatus, L. casei and L. berevis from Ardabil raw milk collection center and Lactobacillus plantarum and Lactobacillus berevis from Sarab milk collection center. Statistical analysis of pH reduction of MRS broth by 6 isolates revealed that there is no significant difference between the isolate's ability during 4 to 48 hours incubation. we conclude that these native species are suitable alternatives for industrial starter cultures.

Hazelnut nutritionally is considered due to containing much oil content, essential fatty acids, phytosterols, antioxidants and minerals. Full-fat dairy products have negative health effects because of its high proportion of cholesterol and saturated fatty acids. In this study, milk fat was substituted with hazelnut oil at levels of 50% and 100% w/w to produce functional cheese; full-fat cheese (FFC) was also made as a control sample to comparison with the cheese samples. Physicochemical properties, proteolysis index and sensorial properties were determined during 80 days of cheese ripening. Results showed that white brined cheeses containing hazelnut oil had significantly (P<0.05) higher amounts of moisture and pH compared to FFC control especially at the end of ripening time. Moreover, proteolysis index increased significantly (P<0.05) in all samples during cheese ripening. In general, cheeses substituted with hazelnut oil at levels of 100% had significantly (P<0.05) higher amounts of pH4.6SN/TN % at the end of ripening period (80th day). NPN/TN% was also significantly (P<0.05) different between FFC and experimental cheeses at the 80th day of cheese ripening time. Furthermore, the results of sensory properties showed that cheese substituted with hazelnut oil at levels of 100% had more overall acceptability score than the other samples at the end of cheese ripening time.

As different kinds of milk and milk products are imported from other cites to Tehran, it is necessary to have further control on these products in order to make sure that they have acceptable qualities. In this study, microbial quality of pasteurized milk collected from Fruit and Vegetables markets in Tehran was evaluated. Microbiological quality of 103 pasteurized milk samplescollected from Fruit and Vegetables Markets in Tehran was evaluated by enumeration of aerobic mesophilic microorganisms, coliforms and detection of Escherichia coli according to Iran's National Standards on expiration date. The result's statistical analysis was performed using SPSS software version 17 and P values less than 0.05 were considered significant. Collected samples were from 13 different brands. Coliforms, Escherichia coli and aerobic mesophilic microorganisms were in accordance with Iran’s National Standard’s limits in 78.6 percent (<10 CFU ml-1), 92/9 percent (absence of Escherichia coli) and 40.8 percent (<7.5× 104 CFU ml-1) of the studied samples, respectively. Only 6.8% of the studied samples had unacceptable levels of all three microorganisms. According to packaging type (bottle and bag), total aerobic mesophilic microorganisms count, coliforms count and Escherichia coli contamination were not statistically significant. Although coliforms count mean was higher than the standard limits, coliforms count had an acceptable level in 78.6 percent of the samples. The results of the present study confirmed the partial satisfactory quality of pasteurized milk packages in Tehran.

Gelatin is a valuable proteinous material that is extracted from fisheries wastes with chemical usual methods. Because the abundance of fishes waste used and because production of gelatin have not high cost, and it frequently is used in the food, pharmaceutical and industrial, It seems extracted gelatin from selected fishes waste is economic efficiency and cost-effectiveness. Aim of this study, extraction of gelatin from common carp (Otolithes ruber) and Largehead hair tail (Trichiurus lepturu). in this studied for production of gelatin the acidic and alkaline processes were used. The samples were immersed in 100 mL of NaOH % 0.5 in three times for 40 minutes and after neutralizing; the samples were immersed for in 100 mL of sulfuric acid % 0.5 three times for 40 minutes. After neutralizing samples were placed in citric acid, 0.5%, 1.5% and 3%. After re-neutralizing, samples were heated for 4 hours for production of gelatin. In finally, each sample were filtrated and dried. The results showed that common carp skin in pH = 6.5 had gelatin yield of 10% based on dry matter. Production yield of gelatin from fish Largehead hair tail in first, second and third treatments at pH = 6.5 were 5.1 %, 7.3 %, and 1.3 % respectively. However, the temperature effect (three levels 70, 75 and 80°C and pH (level 5.6) were evaluated on the gelatin yield content. According to the results of the project, with a temperature of 70°C and pH with 5.6, gelatin yield was the highest and best quality.