Journal of Food Technology and Nutrition
Year:2013 | Volume:10 | Issue:2 (38)|Papers Count:13

Introduction: In recent years the use of ultrasound as a non-thermal and non-destructive method with the advantages such as high efficiency, simple application and low maintenance costs has been introduced to the food industry.Materials and Methods: In this research study the effect of ultrasonic homogenization on water holding capacity of yoghurt has been steadied and compared to the homogenized yoghurt produced by conventional homogenization method. In ultrasonic treatment, three different amplitudes (20, 50 and 70%) and two exposure times (3 and 6 min) were employed.Results: It was observed that ultrasonic homogenization had more effect on water holding capacity as compared to conventional homogenization. As the exposure times and amplitude levels increased, the water holding capacity increased. The highest water holding capacity (66.18%) was obtained at 70% amplitude level for 6 minutes. pH changes in the samples were similar to pH changes in control samples.Conclusion: Application of ultrasonic homogenization improved this process as compared to the conventional homogenization and increased the water holding capacity of the yoghurt.

Introduction: Achieving optimum drying conditions can affect the processing time and improves the quality of raisin produced.Materials and Methods: In this research, the effect of two- step temperature and pretreatments on some qualities of the final product in drying of Thompson seedless grape were studied. Drying was carried out by two methods. In the first method of drying, the grapes were subjected to conslaut temperatures of 50, 60, 70, and 800C. In the secound method of drying the grapes were subjected to a temprature of 800C and when the moisture content of the product was reduced to 50%, the temperature was reduced to 50, 60 and 700C and the processing was continued at the set temprature. Four pretreatments consisting of hot water, %5 potassium carbonate, %0.4 olive oil and %0.5 sodium hydroxide were performed on the samples. A blank sample without pretreatment was used as a control.Results: The results indicated that factors such as temperature and pretreatment have significant effects on browning rate, dehydration and shrinkage, but there was not a significant effect on the acidity.Conclusion: Raisins dried at two-step temperatures by changing the second step’s temperature to 600C and pretreated with %5 potassium carbonate, %0.4 olive oil and %0.5 sodium hydroxide had better quality.

Introduction: The objective of this research work is to study the effect of microbial transglutaminase enzyme on the emulsifying properties of silver carp fish myofibrillar proteins (MP) by means of response surface methodology (RSM).Materials and Methods: Central composite design (CCD) was applied to study the effect of enzyme activity on the emulsion stability. This study has been carried out at different enzyme activities (0, 0.25, 0.63, 1.01, and 1.25 U/mg protein) and setting times of 30, 109, 225, 341, 420 min and incubation temperatures of 5, 13, 25, 36 and 45 on the stability of emulsion using silver carp fish myofibrillar proteins (MP). The emulsion stability (ES) of MTG-treated MP was measured after 4 and 24h, at 4oC.Results: The results showed that there are significant interactions between sitting time and incubation temperature and enzyme activity on ES (P<0.05).Conclusion: The enzyme activity caused increased cross-linkage in the protein structure and improved the viscoelastic properties of interfacial layer.

Introduction: Lactobacillus casei has a great potential to be applied in the production of probiotic dairy products like yogurt. Therefore, according to the high consumer acceptance and positive properties of probiotic yogurt containing Lactobacillus Casei, the effect of microbial cultures inoculation order and incubation temperature on the quality and viability of probiotics in the product were evaluated.Materials and Methods: The effect of Inoculation order (simultaneous inoculation of yogurt bacteria and Lactobacillus casei, the initial inoculation of Lactobacillus casei and secondary inoculation of yogurt bacteria, initial inoculation of yogurt bacteria and secondary inoculation of Lactobacillus casei) and incubation at temperatures of 37°C and 40°C were investigated.pH value, acidity, percentage of serum removing (synersis), probiotic counts and sensory evaluation concerned with taste, color and texture were compared with the control sample (yogurt without probiotic bacteria). The high quality sampels were selected and were stored at 4°C for 21 days. During this period physicochemical properties and probiotic counts were evaluated.Results: The results showed that simultaneous inoculation of yogurt bacteria and Lactobacillus casei at both 37°C and 40°C caused the best organoleptic properties. The results of evaluations on selected samples showed that during cold storage the sample incubated at 37°C had the lowest percentage of synersis and the largest number of live probiotic bacteria.Lowest pH value and highest acidity were observed in the sample that was incubated at 40°C.Conclusion: This study showed that combined cultures of yogurt bacteria and Lactobacillus casei incubated at 37°C provided better quality of product in respect of sensory properties and viability of probiotic bacteria.

Introduction: Cannabis has been known for over 2000 years. Many scientists have been interested in its oil due to its valuable nutritional and pharmaceutical properties. Ultrasound assisted extraction (UAE) is an emerging potential technology that can accelerate the heat and mass transfer and has been successively employed in the extraction field. Ultrasound waves after interaction with the plant material alter its physical and chemical properties and the effect facilitates the release of extractable compounds and enhances the mass transport by disrupting the plant cell walls. UAE allowed better yields and a lower extraction temperature as compared to the conventional methods.Materials and Methods: In this study, Box-Behnken design was used to investigate the extraction condition of oil from cannabis by ultrasonic method. The factors investigated in the ultrasonic method were temperature (30, 45 and 60oC), liquid/solid ratio (5: 1, 10: 1, 15: 1) and time (30, 60 and 90 min) at the frequency of 35 KHz. Experiments were designed according to the central composite rotatable design. In this study, response surface methodology was used to optimize the ultrasonic extraction condition to obtain the maximum oil.Results: With respect to the dependent variables, both linear and quadratic effects of all of the three independent variables on extraction of oil were found to be significant (p<0.001).The optimal conditions in ultrasonic assisted extraction method were the extraction temperature of 60oC, extraction time of 90 min andliquid/solid ratio of 12.37: 1. Under these conditions, the oil yield from cannabis was 78.04%.Conclusion: The mathematical model developed was found to fit well with the experimental data of oil extraction. The most suitable condition for extraction of oil was found to be a single step extraction. Ultrasound assisted extraction improved the yields since the method is fast and operates at low temperature and the final product usually showed less thermal degradation than traditional methods.

Introduction: Osmotic treatment is based on placing food into a hypertonic solution that has higher osmotic pressure and lower water activity than the food in question. Food dehydration due to some known reasons might cause deterioration and unacceptable changes in the final product. Therefore in some cases it is necessary to use some pretreatments such as osmoic dehydration.Materials and Methods: In this research, during osmotic dehydration of pear rings, the effects of concentration of sucrose solutions of 50 and 60 percent (w/w), and reconstituation of osmotic solutions (5 times), in the constant temperature of 300C, were investigated.Quantitative and qualitative characteristics of the samples, such as total sugar, moisture content and mass transfer phenomena including water loss (WL), solid gain (SG) and productivity ratio (WL/SG) of osmotic process were taken into consideration.Results: The results showed that SG and WL increased and decreased respectively by increasing the concentration of osmotic solution. The results also indicated that the productivity ratio of osmotic process increased with reusing and reconstituating the osmotic solutions, for 5 times.Conclusion: It was concluded that the samples obtained after 5 times reconstituating with osmotic solution in concentration of 50%, were superior samples.

Introduction: Frying is a popular method for preparing food with unique characteristics.However during frying unwanted changes occur in the oil, that not only has adverse effect on the quality of frying oil and fried product but also has adverse effect on the consumer’s health. The object of this study was to monitor changes in canola oil quality during vacuum and atmospheric frying.Materials and Methods: potato strips were fried in canola oil under atmospheric and vacuum conditions for 4 consecutive days, 4 times in each day. Atmospheric frying was performed at 180oC for 9 min, vacuum frying was done at 120oC and 200 mbar for 13 min. The quality of oil samples such as fatty acid composition, calculated oxidizability (Cox) Value, peroxide value (PV), p-anisidine value (p -AV), totox value (TV) and acid value (AV) were evaluated.Results: For both frying methods, saturated fatty acids were increased significantly (p<0.05), but unsaturated fatty acids were not changed significantly (p≥0.05). In the first day of atmospheric frying, PV, p -AV and TV were raised, but in other days decreased significantly (p<0.05). All the mentioned chemical factors increased gradually under vacuum frying and were lower significantly (p<0.05) in comparison with those measured in atmospheric frying.In both methods of frying AV increased with frying time. It is assumed that the high concentration of oxygen as well as higher temperature in atmospheric frying has affected the quality of frying oil.Conclusion: Vacuum frying is an alternative method for reducing the oil deterioration and increasing the shelf life.p -anisidine and totox values are considered to be factors for monitoring the quality of frying oil in respect of frying time.

Introduction: Tarkhineh soup is one of the traditional foods consumed in the west part of Iran due to its medical and pharmaceutical properties. Studies have indicated that tarkhineh is a good source of probiotic bacteria. Therefore molecular identification of lactobacillus strains of tarkhineh by 16S rRNA gene sequencing might be considered essential.Materials and Methods: 4 isolates (T20, T22, TD4, TD10) were selected for molecular identification. Samples were grown in MRS broth and total genomic DNA was extracted by lysosyme extraction protocol. PCR-mediated amplification of the 16 S rDNA was carried out by specific primers. Identification of bacterial isolates was performed based on 16s rDNA partial gene sequence method for both strands with the same primer used in PCR.Results: These strains produced the high level of bacteriocin.16S rRNA genes were sequenced and deposited as a novel stains in Gen Bank. The sequences were compared with other rRNA sequences available in the NCBI database and the high similarity (99%) to speciesL. casei was estimated for the sequence isolates.Conclusion: Due to the high potential of probiotic bacteria in tarkhineh, these strains might be considered useful and could be employed in food industry.

Introduction: Oxidation and polymerization of vegetable oils and fats particularly during frying is a major problem that the consumer and the industry is faced with. In the past some vegetable oils such as sunflower seed oil due to its economical aspects and chemical and physical characteristics might have been recommended for frying practices, but there were not the ideal oils for frying procedures particularly for industrial applications. Therefore the object of this study is to formulate a frying oil based on tallow olein and palm olein within the defined standard for this type of product.Materials and Methods: Beef tallow was obtained by dry rendering fallowed by fractionation at 4oC for 22 hours. Palm olein was obtained from the main supplier of this product.11 samples were produced by mixing the two fractions at different ratios. Series of chemical and physical tests consisting of melting range, refractive index, peroxide value, iodine value, saponification value, smoke point, induction period and fatty acid composition were carried out on the prepared samples.Results: The results indicated that mixtures of the two fractions might be employed as frying media within the standard defined and there were significant differences between the results obtained from different mixtures.Conclusion: The mixtures of 70% palm olein: 30 % tallow olein, 80% palm olein: 20 % tallow olein and 90 % palm olein: 10% tallow olein agreed with the national standard for frying oils but the best mixture was the combination of palm olein and tallow olein at the ratio of 70:30.

Introduction: Good and safe keeping of perishable foods in food shops is one of the most important factor particularly concerning the children, pregnant women, elderly and patients.This survey has been carried out in Takistan in order to evaluate the ways that perishable foods are preserved in the shops.Materials and Methods: This is a cross-sectional study with a questionnaire concerning the demographic and sanitary informations of the retailer. The forms were completed during direct inspection. 100 questionnaires were completed in 4 different parts of the city (north, east, west and south).Results: 96% of retailers in respect of hygienic parameters worked within the standards defined. 70% of the shops and relailers had refrigerator or cold store room. 40% of the retailers over loaded the refrigerator with foods. Only 70% of the shops and retailers keept the perishable foods in the cold storage room or refrigerator. Young and middle aged managers particularly those who completed courses in food safty and hygiene acted better and more responsible in presenting heathy and safer foods to the consumers.Conclusion: This study indicated that the knowledge of food and food hygiene for the persons managing the food premises is essential in order to present the consumer with a safe and healty product. This study also showed that zones with higher living standard acted better and more responsible in respect of food hygiene and preservation.