فصلنامه پژوهش های صنایع غذایی
سال بیست و چهارم شماره 1 (بهار 1393)

Moisture sorption isotherms are useful in predicting shelf-life stability and in calculating the variations of moisture content during drying, storage and packaging. In this study, the moisture sorption isotherms for pretreated seedless grape were determined using a static-gravimetric method at 40, 50, 60 and 70 C, and the effect of pretreatment solutions on the isotherms was investigated. In order to describe the sorption moisture isotherms, the BET, GAB and Halsey equations were tested to fit the experimental data by using non-linear regression analysis method. According to the modeling results, the GAB and Halsey equations gave the best fit for the samples. The net isosteric heat of desorption was calculated according to the obtained isotherms at different moisture content.

Mycotoxins are highly toxic secondary metabolites and carcinogenic compounds that are produced by species of Aspergillus, especially Aspergillus flavus and Aspergillus parasiticus. In this study, total aflatoxin and aflatoxin M1 were identified and determined in milk and meat samples of 30 buffaloes slaughtered in the industrial slaughter-house of northwest of Iran. Samples were transferred to the “Food Hygiene and Quality Control Laboratory” Faculty of Veterinary Medicine, University of Tabriz under standard conditions. Preparation of samples was done according to the instructions contained in each of the ELISA kits. The results showed that all samples are contaminated by total aflatoxin and aflatoxin M1. The Mean value for total aflatoxin in milk and meat was the 0.72±1.63 ng/ML and 0.34±0.48 ng/g, respectively the highest mean level of total aflatoxin was observed in the milk samples. Total aflatoxin level of all samples was lower than the standard limit for total aflatoxins in food (2-4 ng/g). The highest mean values of aflatoxin M1 (26.65±1.46ng/L) is related to the milk samples. However, 12 milk samples (40%) contained aflatoxin M1 above the standard limit (50ng/L). Milk, dairy products and meat are an important source of protein and minerals which are widely used by all age groups. Thus aflatoxin contamination of these products is a serious threat for consumers, especially children and prevention of feed contamination by mycotoxin especially aflatoxin is suggested.

For exerting beneficial health effects of probiotics, they should be administered alive and in adequate amounts. Therefore, selection of suitable carrier for delivery of this beneficial bacterial cells and evaluation of physicochemical and sensorial properties of the final product is necessary. Lactobacillus casei was used for producing fermented probiotic soy ice-cream. Physicochemical and sensory properties of fermented probiotic soy ice-cream and control sample were evaluated. MRS-Agar was used for probiotic enumeration. There were significant differences (P<0.05) in acidity, pH, overrun and density of fermented probiotic soy ice-cream in comparison with control sample, but no significant differences in fat, total solids and melting resistance of both ice creams (P≥0.05). Probiotic count before freezing was 3.1×106 CFU/g that was showed no significant decrease during 3 months storage at -24˚C and there were 106 CFU/g viable probiotic cells in the final product. Texture and color of fermented probiotic soy ice-cream were more acceptable in comparison with control sample. The results demonstrated that fermented soy ice-cream is a suitable vehicle for delivery of probiotic bacteria among consumers.

Response surface methodology was used to study the effects of antibrowning agents (citric acid, oxalic acid, sodium chlorite, sodium metabisulfite) and osmotic dehydration (concentration and immersion time) on the color and rheological properties of apple rings with intermediate moisture level. The selected color parameters were L*,a*,b*, and sensory color scores and texture parameters were storage module (G΄), complex module (G*) and sensory texture scores. The numerical optimization indicated that the optimum condition was 0.277 % (w/v), 0.50% (w/v), 0.0% (w/v), 0.50% (w/v), 30% (w/v) for citric acid,oxalic acid,sodium chlorite, sodium metabisulfite and osmotic solution,concentration, respectively and the optimum immersion time was 15 minutes. The corresponding response values for L*,a*, G*, sensory color scores and texture scores predicted under the optimum condition were 84.62, -1.38, 76.56, 78.67, 10.96 and 6.30, respectively.

Potato is one of the strategic agricultural products and is a main food in many of developing countries. Potato chips and slices are one of the most important industrial products. The use of inappropriate varieties as raw material in Iran is one of the challenges of processing. This study was conducted to evaluate and compare the physical and mechanical properties of three potato varieties (Agria, Almera and Marfona) in order to address the most suitable variety for the production of potato chips and slices. For this purpose, the physical and some mechanical properties of the varieties, including modulus of elasticity, coefficient of restitution and punching energy were determined and compared. Prior to determination of the mechanical properties, in order to provide the same experimental conditions for three varieties, some factors affecting on the modulus of elasticity and coefficient of restitution of tubers were evaluated. The results showed that three varieties were not significantly different for physical features. Therefore, one of the varieties cant be selected according to the physical features. But comparison of mechanical properties of three varieties showed that the Agria variety had the highest values of mechanical features, and its texture is more uniform compared to other two varieties. The advantage of this variety makes it to absorb less oil in their tissues in the process of frying. This reduces grease and sticky texture of the chips. Also, that would reduce the product cost remarkably.

Barberries (Berberis. Spp.) are one of the herbal plants that different parts of it like roots, leaves, barks and fruits have long been used as medicine in Iran. Besides, seedless barberry (B. vulgaris), which is cultivated as a domestic plant, other species (B.integerrima and B.crataegina) in different parts of Iran grow in wild conditions. Access to scientific information concerning the physical properties of Berberis species for optimum design of storage, transportation, sorting, processing and packaging equipment is important. Identification of the chemical characteristics of Berberis species can create a basis for using them in the pharmaceutical or food industries. Therefore, in order to in-troduce these native species, physical and chemical characteristics of two wild barberries and seed-less barberry were evaluated. Results showed that there was statistically difference between length, surface area, bulk density, thousand mass, and terminal velocity of these species. Compared to seed-less barberry, wild barberries because of their seeds had high amount of fat, protein, total carbohy-drate, ash and crude fiber. Wild barberries had high acidity and low pH. Potassium was the major mineral in all three species. B.cratagina contained the highest amount of anthocyanin (4684.037mg/l) followed by B.integerrima (998.17mg/l) and B.vulgaris (280.96mg/l). The differ-ence between chemical properties of B.cratagina and B.integerrima seeds were significant.

In this study, artificial neural network (ANN) model was used to predict the average permeate flux and NaCl rejection in nanofiltration process of sugar industry decolorization columns waste water. Nanofiltration process was performed at three temperatures 30, 4 and 50°C, at three pressures of 1, 1.5 and 2 MPa, at three concentration levels 60, 80 and 100 g/l and at two pH levels 8 and 9. In order to predict the permeate flux and NaCl rejection multi-layer perceptron neural network with 4 inputs and 2 outputs were used. The results showed a network with 9 neurons in hidden layer and using a hyperbolic tangent transfer function and the Levenberg–Marquardt (LM) optimization technique and 30%-30%-40% data for training/ testing/ validating process can be well predict the permeate flux (0.98) and NaCl rejection (0.88) in the nanofiltration of decolorization column wastewater. Sensitivity analysis results by optimum ANN showed the pressure was the most sensitive factor for prediction of both flux and rejection by the selected ANN.

Packaging is one of the important factors in determining storage life of foods and nanotechnology can extend this life by improving the quality of packaging materials. In this study, the effect of packaging materials containing nano-silver and nano-clay silicate particles on postharvest quality attributes and shelf life of sweet cherry (Prunus avium) cv. Syaahe Mashhad fruits was studied after 45 days storing at 1 ± 1 °C and 90% ± 2 relative humidity. For this purpose, the amount of antioxidant, marketability, total acidity, total phenolic compounds, vitamin C, fruit decay, fruit pedicel browning index, pH, and total soluble solids of fruits were evaluated during the storage period. The results indicated that in comparison with common polymeric packaging material, the packages containing nano-silver particles based on polyethylene significantly caused to retain antioxidants quantity. Moreover, the packages containing nano-silver and nano-clay silicate particles effectively kept vitamin C, total phenolic compounds and fruit marketability.

Indian Neem (Azadirachta indica L.) leaf was extracted by three different extraction methods (Decoction, Percolation and Maceration) using two different solvents; methanol 80% (v/v) and water. Determination of total phenolic content by Folin-Ciocalteu method revealed that methanol 80% (v/v) for 7 days (maceration method) cause the highest quantity of extracted phenolic compounds. Meanwhile, determination of radical scavenging activity of three different extracts by DPPH method indicated that methanol 80% (v/v) for 24 h (percolation method) cause the highest RSA and was considered as the most effective extract. Furthermore, qualitative and quantitative characterization of phenolic compounds of percolation extract as the effective extract using HPLC revealed that Nimbolide (2896.05 mg/100 g extract) is the main limonoid triterpen followed by phenolic acids and 2′, 3′-dehydrosalannol which are 635.38 and 531/94 mg/100g extract, respectively. Determination of antioxidative effects of percolation extract in refined soybean oil (without antioxidant) using accelerated oven test (13 days, 60℃) declared that soybean oil containing 2000 ppm of the percolation extract was more stable than other concentrations until 4th day in terms of hydroperoxide when the aforementioned concentration was able to make the oil more stable until 13th day in terms of aldehydes and ketones.

Irradiation as an effective non thermal sterilizing method of meat preservation has excellent potential to extend the shelf life. In this study, quail meat was irradiated at doses of 0, 1.5, 3 and 5 kGy of electron beam irradiation and was kept in a refrigerator (4 ± 1°C) for 15 day. Then effect of irradiation and maintenance of refrigeration temperature were evaluated on microbial quality, chemical and organoleptical properties. The results of microbial analysis indicated that irradiation dose of 1.5, 3 and 5 kGy caused a significant decrease (P<0.05) in the number of aerobic mesophilic bacteria, lactic acid bacteria, fungi and yeasts. Irradiation dose of 1.5 and 3 kGy caused a significant decrease (P<0.05) in the number of coliforms. Microbial load of control and irradiated samples increased significantly (P<0.05), that speed of this increase was greater in the control samples, during the storage period under refrigerated conditions. The shelf life of irradiated samples was higher than 15 days while control samples were kept only 4 days under the same conditions. Irradiation significantly (P<0.05) increased the initial TBA of samples and storage in refrigerator was led to increase the TBA value significantly (P<0.05) in all samples. Irradiation had no significant effect on the organoleptical properties (P>0.05) and caused shelf life to increase of more than 15 days but, the control samples were kept only 5 days under the same conditions. Thus, this study clearly indicated that the electron beam irradiation of quail meat has positive effects on its overall characteristics and extend the shelf life during refrigerated storage.

In this study, survival of Bifidobacterium lactis (LAFTI-B94) was investigated in both free and encapsulated forms and their effect on physicochemical and sensory properties of yogurt samples during storage for 28 day at 5±1°C. Treatments including: C (control, no probiotic) and Bifidobacterium lactis in free and encapsulated form. The analysis of the results showed that the number of B. lactis in free form in yogurt samples decreased significantly (P<0.05) during storage. The encapsulated form in yogurt samples increased about 1 log in comparison with free form during storage. Also the encapsulated forms of probiotics bacteria increased amount of exopolysaccharides and viscosity of yogurt in comparison with control sample (P<0.05). According to the results of sensory evaluation, significant difference was not observed between both samples of yogurt from a flavor and texture point of view. Therefore, it was concluded that, the encapsulated Bifidobacterium lactis can be used successfully in the production of probiotic yoghurt.

In this study, effect of storage temperature on survival of free and encapsulated Lactobacillus acidophilusin in apple juice and physicochemical and sensorial properties of final products was investigated during 60 days storage at ambient (25 ± 5°C) and 5 ± 1°C. There were three treatments in two replicates, including: 1. Control apple juice (CAJ), 2. Apple juice containing Lactobacillus acidophilus in free form (FPAJ) and 3. Apple juice containing Lactobacillus acidophilus in encapsulated form (EPAJ). The results showed that the encapsulation caused an increase of 1 log in the number of L. acidophilus in both storage conditions. Moreover, the number of probiotics in the kept samples at ambient was 1.5 log cycle greater than those kept at 5 ± 1°C at the end of storage. The Lactobacillus acidophilus in encapsulated form had not significant effect in transparency and turbidity (P>0.05), but the L. acidophilus in free form decreased transparency and increased turbidity in apple juice. The results of sensorial evaluation showed that using of L. acidophilus in apple juice had not adverse effect on color and flavor in samples. At the end of the storage period, except the treatment FPAJ stored at 5 ± 1 °C, the number of L. acidophilus in the rest of samples was greater than minimum number of the recommended therapeutic products (106cfu/g). In despite of high number of L. acidophilus in treatments stored at 25 ± 5 °C, to prevent the possibility of fermentation in ambient temperature and to increase shelf-life, it is recommended to store such products at 5 ± 1°C. Therefore, L. acidophilus in capsulated form could be used successfully in apple juice not only caused no adversary affects in the physicochemical and sensorial properties, but also increased survival of it’s probiotics.