نشریه فرآوری و نگهداری مواد غذایی
سال ششم شماره 1 (پیاپی 15، بهار و تابستان 1393)

To evaluate the effect of replacing the almond meal on viscoelastic properties of rice cake، stress relaxation test was carried out. Stress relaxation test were conducted using a texture analyzer machine. Constants of the Peleg - Normand and the extended Maxwell model for variables were calculated. The results showed that with increasing strain rate increased amount of K1، K2 and decay forces، hence the rice cakes is higher elasticity in high strain rate، However at low strain The cake behavior is further viscous and the elasticity amount was decrease. Replacing the almond meal to 10 percent، reducing the amount of initial force، peleg-normand and extended Maxwell model parameters، however in the higher levels replacement the amount of this parameter is increased. Therefore، increasing the replacement level to 10% almond meal، rheological behavior of cake was indicative liquid-like viscoelastic behavior and in the higher levels replacement dough behavior was more amenable to semi-solid. Fitting the experimental data with Peleg Normand and Maxwell models shows the better performance Maxwell model was for fitting data.

Todays, essential oils from aromatic plants have been qualified as natural antioxidants and proposed as potential substitutes of synthetic antioxidants in food products. In this research chemical compositions and antioxidant activity of artimisia essential oil on oxidative stability of frying oil were analyzed. Essential oil was extracted by hydro distillation and its chemical composition was determined by the GC-MS. Folin-Ciocalteu reagent was used to estimate total phenolic content. The antiradical activity of essential oil was assessed by using ABTS (2, 2’-azino-bis (3-ethylbenzthiazoline -6-sulphonic acid) and DPPH (2, 2-diphenyl-1-picrylhydrazyl) methods and compared with TBHQ as a synthetic antioxidant. The antioxidant activity of essential oil was evaluated against TBHQ in deep oil frying by peroxide value and thiobarbituric acid index under accelerated condition.Alpha thujone (53.50%) and beta thojone (14.66%) were the main components of artimisia essential oil. Total phenol content of essential oil was determined to be 7.5 mg gallic acid equivalent in 1 gr of dried sample and EC5 was 1 mg/ml in DPPH. ABTS test showed that 2 mg/ml of essential oil had the highest antiradical activity (0.08 mg/ml ascorbic acid equivalent). In oven test, 1000 ppm of essential oil had the higher activity than in 200 ppm of TBHQ. All concentrations of artimisia essential oil showed antioxidant activities and various concentrations were able to slow down the oxidation process. This essential oil could be used as natural antioxidant in foodstuffs, especially those containing lipid, due to its reaction with oxidative radicals and can increase shelf-life of those food.

In this study production of Iranian UF white cheese with probiotic strains of Lactobacillus acidophilus and Bifidobacterium lactis was investigated. Cheese samples were ripened at 6°C for 60 days. The viability of probiotic strains and chemical compositions such as dry matter، pH، salt، protein and fat were assayed during ripening days. Cheese samples also were analyzed in terms of textural properties using texture profile analyzer (TPA) and sensory evaluation during this period. The counting results showed that the Lactobacillus acidophilus present in the sample namely، LP، was 8. 023 log cfu/gr at the first day of production. It reached 6. 11 log cfu/gr after 45 days، whereas counting of Bifidobacterium lactis in the BP sample was 8. 01 log cfu/gr at the first day of production and reached 6. 08 log cfu/gr after 45 days. The cell number of live probiotics by the end of 45th day was higher compared to the value considered as necessary for probiotic beneficial effect. pH of all cheese samples decreased. While the criteria of salt، acidity and protein content increased and the fat content and dry matter of all cheeses did not change significantly during the storage time. The sensory evaluation showed that the samples containing Lactobacillus acidophilus acquired the high extent of texture and flavor. Rheological evaluation showed hardness decrease at the end of ripening days.

The aim of this research was to survey of using soy protein isolates and tragacanth gum as egg substitutes in mayonnaise formulation. The mayonnaise prepared with difierent compositions of soy protein isolate، egg، and tragacanth by applying the optimal mixture design method and effect of this substitution on its stability، heat stability، viscosity، texture، physicochemical and sensory characteristics of mayonnaise were considered. According to the results، with an increase of replacement tragacanth and soy protein isolates، stability in samples 4،5، 6 and 7 increased. Generally،all treatments showed stability higher than 98%. Viscosity all treatments except treatment 2 and 9 (respectively،23. 92 and 32. 02 pa. s) Compared to the control sample increased and in total there are statistically significant differences between all samples. Generally، samples containing soy protein isolates and tragacanth، had acceptable quality in terms of investigated properties. The highest rating from Sensory properties was awarded to treatment 5 (55/55% replacement with soy protein isolates with tragacanth). So، with the right concentration of tragacanth and soy protein isolates، egg mayonnaise can be greatly reduced.

Date syrup، date concentrate and date liquid sugar are among the products which are produced from low quality dates in date processing plants. The aim of this research was to investigate chemical characteristics and sensory properties of date syrup، date concentrate and date liquid sugar in comparison with sugar (sucrose) solutions and evaluate possible substitution of sucrose with these date by products from different technological aspects. Firstly date syrup، date concentrate and date liquid sugar were produced in an industrial scale production line and then chemical composition including moisture، ash، protein، pH، fat، Brix and fatty acids were determined. Then solutions with concentrations similar to most food applications were prepared from date syrup، date concentrate and date liquid sugar and their sensory properties (sweetness، consistency، flavour، color and overall acceptability) were measured and compared with their corresponding sucrose solutions. The chemical composition results showed that date syrup had more nutritional compounds than date concentrate and date liquid sugar. Sensory results also revealed that date liquid sugar was more similar to sucrose solutions than date syrup or date concentrate، although date liquid sugar has been refined extensively and therefore more beneficial compounds have been eliminated.

In this study، the effect of retentate and whey protein concentrate in different concentrations on the properties of low fat synbiotic yoghurt was studied. Retentate samples containing different concentrations of the three concentrations (0. 5، 0. 75 and 1 %) and Whey Protein Concentrate (0. 2، 0. 3 and 0. 4 %) were prepared and characterized in terms of physicochemical، rheological and sensory and survival of Lactobaculus Casei bacteria at 1، 7 and 15 days after production was evaluated. All of the samples added the amount of 0. 6% inulin as prebiotic ingredient. Control samples did not add any combination of enrichment. The results showed that the increase in acidity during storage. Compared with control samples containing whey protein concentrate، yogurt sample containing retentate due to the presence of minerals and vitamins، such as vitamin B groups of more Lactobaculus Casei were counted. The results showed that the viscosity was lowest in the control. On the other hand، during the storage period، a slight increase in viscosity was observed. The sensory evaluation showed that sample retentate Synbiotic formulated with 0. 5 % by the highest score of all quality indicators were examined.