فصلنامه پژوهش های صنایع غذایی
سال بیست و سوم شماره 2 (تابستان 1392)

Response surface methodology (RSM) was used to evaluate the effects of whey protein concentrate، X1، (0. 7-2. 8 % w/w) and caseinsodium، X2، (0. 7-2. 8 % w/w) as a substitute for eggs، and carboxymethylcellulose، X3، (0. 66-0. 234 % w/w) as thickening agent in salad dressing on the stability and particle size of salad dressing. The central composite experimental design was used and the data were analyzed using RSM. The results of analysis of variance (ANOVA) showed that P values of all models were significant and lack of fit P values was no significant at the level of 95%. Therefore، the adequacy of models was acceptable. From the empirical models obtained by RSM in this study، the optimal values of independent variables for the stability of the salad dressing were obtained: 1. 68% for whey protein concentrate، 1. 68% for sodiumcaseinate، 0. 168% for carboxymethylcellulose (% w/w). Based on the results، the optimum level of these variables with the lowest fat droplet size was: 2. 8% for whey protein concentrate، 2. 8% for caseinsodium، 0. 234% for carboxymethylcellulose. The results indicated that using whey protein concentrate، sodiumcaseinate and carboxymethylcellulose reduced oil droplet size and increased stability during centrifugation in salad dressing. Therefore، milk proteins can be used as a substitute for eggs in salad dressings.

The main aim of this study was to determine the effects of different levels of heat-moisture treated (HMT) wheat starches produced under varying treatment durations on the properties of dough and bread. Therefore، native wheat starch with moisture content of 25% was stored at 105 °C for 14، 16 and 18 h to produce HMT1، HMT2 and HMT3، respectively. Then they were dried to an average moisture content of 11. 5% and sieved to particle size of 200 µm. The modified starches were used at 0، 10، 20 and 30% in the formulation of loaf bread. The farinograph results showed a significant decrease in the water absorption of the sample containing HMT3، while other samples were similar to the control. Dough stability time increased when up to 20% HMT were used and then decreased. Addition of 30% of each modified starches resulted an increase in dough softening. The hardness of the bread increased as the level of HMT increased. Addition of HMT2 and HMT3 resulted in harder bread texture compared to the HMT1. The volume of the bread containing 30% HMT was the lowest while the control and the sample made with 10% HMT1 had the highest volume. The HMT starches could delay water migration from bread crumb to the crust. Heat-moisture treatment time was a determining factor influencing the properties of the produced starch and the resultant dough and bread.

Kefiran is an exopolysaccharide which is produced mainly by lactic acid bacteria and fungi in kefir grains during growth. In this study، kefiran was added at levels of 1، 2 and 3% w/w (flour basis) to wheat flour and its effects on physicochemical characteristics of wheat and flour and rheological properties of dough was investigated. Physicochemical properties of wheat and its flour were analyzed by inframatic and the rheological of dough by farinograph and extensograph instruments. The results of physicochemical properties of the tests wheat and its flour showed that wheat had hectoliter and thousand seed weight، water absorption، flour yield and falling number higher than standards، whereas its hardness، wet gluten، moisture and protein content along with zeleny index and SDS-sedimentation height were higher than those of standards. Results of farinograph evaluation of dough showed that addition of kefiran significantly (P<0. 05) increased dough water absorption، dough development time، departure time and valorimeter value، while decreased mixing tolerance index and dough degree of softening after 10 and 20 minutes. Nevertheless، dough stability did not change significantly (P<0. 05). The results of extensograph showed that kefiran significantly (P<0. 05) increased resistance-to-extension and energy for extension in over the time while، dough extensibility was significantly (P<0. 05) decreased due to increasing levels of kefiran. It was concluded even though kefiran had no significantly effect on dough stability، could significantly increase resistance-to-extension and decreased mixing tolerance index and dough degree of softening after 10 and 20 minutes. Therefore، kefiran can be used to improve rheological properties of weak dough and its processing conditions.

Bread has a major role in diet of people in Iran. One of the important factors affecting the quality of bread is the quality of wheat flour. In this research، the effects of combined application of organic and nitrogen fertilizers were studied on physicochemical properties and bread-making quality of wheat (Triticum aestivum cv. Alvand). Physical properties of grain، quality characteristics of flour as well as bread quality were measured in each treatment. The results showed that wet gluten and crude protein contents، test weight، seed 1000-weight، Zeleny sedimentation values and Pelshenke number of the flour and bread volume and height were significantly increased by application of urea fertilizer in soil (p≤0. 05)، while urea fertilizer had no significant effect on solid density of grain. Application of farmyard manure (FYM)، sewage sludge and municipal waste compost with and without urea fertilizer significantly increased seed 1000-weight، wet gluten، crude protein content، bread volume compared to those of the control. Zeleny sedimentation value was increased by application of sewage sludge and municipal waste compost compared to that of the control، while this value was not affected by FYM application. Application of all three organic fertilizers without urea had no significant effect (p≤0. 05) on test weight but integration of them with urea increased test weight. Application of FYM with and without urea fertilizer and sewage sludge and municipal waste compost without urea fertilizer increased Pelshenke number compared to that of the control treatment. In general، in order to increase wheat flour quality، combination of 30 and 60 ton municipal waste compost or FYM or sewage sludge with 150 kg urea/ha is recommended at similar conditions.

Medicinal hawthorn fruit has health effects on certain physiological systems such as the cardiovascular that these effects are connected with the presence of antioxidants compounds. In this study، total phenolic and flavonoid contents of acetonic and ethanolic extract of hawthorn fruit were measured spectrophotometrically and antioxidant activity of the extracts were assessed by DPPH radical-scavenging activity، total antioxidant capacity and reducing power assay and compared with synthetic antioxidant namely BHT. Also، the effect of acetonic extract on oxidative stability of soybean oil was assessed using peroxide value and thiobarbitoric acid index. Results showed that the highest phenolic and flavonoid content 100. 75mg GA/g extract and 2. 14 mg QU/g extract، respectively and also the most of antioxidant activities in whole of assays were related to the acetonic extract. This extract showed antiradical activity higher than BHT only in DPPH assay. Also، the extract at concentration of 1000 ppm effectively inhibited the formation of peroxides in soybean oil and revealed strong antioxidant activity compared with BHT at concentration of 200 ppm. Therefore، it can be concluded that hawthorn fruit is a good source of phenolic compounds and other natural antioxidants.

Mechanical characteristics of agricultural crops are important to optimum design of milling، planting and harvesting machines and also for reducing losses and to improve quality of crops during harvest stage. In this study، mechanical properties of pistachio nuts (rupture force، deformation، rupture energy and toughness) were investigated. Mechanical properties were determined through quasi-static loading experiment using a material testing machine. A factorial experiment with completely randomized design was utilized to study the effect of moisture content (at 5 levels: 35، 30، 25، 20 and 15% w. b.)، loading rate (at 3 levels: 10، 20 and 30 mm min-1) and variety (at 3 levels: Fandoghi، Badami and Akbari) on mechanical properties of pistachio nuts. Results showed that all the three factors (variety، moisture content and loading rate) had significant effects on the rupture force، such that by decreasing moisture content the rupture force increased. Also، the nuts rupture force increased by increasing loading rate from 10 to 30 mm min-1. Investigation of the effects of variety، moisture content and loading rate on deformation، rupture energy and toughness showed that these factors had a significant effect on these parameters.

In recent years، natural biopolymers such as starch have been paid more attention as alternatives to the petroleum-derived plastics for packaging films production. Nowadays، different modified starches with novel characteristics were proposed to the market and could be used in producing edible films. In this study، four corn-based edible films namely corn starch، pregelatinized starch، oxidized starch and corn flour were compared in all their physical and mechanical properties. Results showed that films obtained from oxidized starch have good appearance and transparency but because of high solubility and water vapor permeability (WVP) besides poor mechanical properties، is not much favorable candidate. Pregelatinized corn starch films were similar in many characteristics to simple corn starch but their WVP were high and did not have appropriate tensile strength. Films from corn flour were compatible in many functional aspects to simple corn starch films. However، all four type films exhibit highly biodegradable property.

Phenolic compounds are useful ingredients of date palm pit and usually exert high antioxidant activity. The aim of present study was to investigate the effect of heating and acidification on total phenolic content and antioxidant activity of date palm pit extract by using the Folin–Ciocalteau and ABTS reagents، respectively. Results showed that total phenolic content increased with increasing the heating temperature (70–110 °C) and time (10–40 minutes). The palm pit extract treated at longer heating times exhibited higher antioxidant activity. However، acidification of pit extract from its inherent pH 6. 23 to 1. 51 led to a decrease in total phenols content from 1582 to 1068 mg gallic acid equivalent per 100 g dry weight. Acidification also caused a decrease in antioxidant activity. The results of simultaneous heating and acidification treatments showed that increasing influence of heating on total phenolic content was more effective than decreasing influence of acidification on phenols content.

Mayonnaise is an oil in water emulsion which is stabilized by egg components. In this research، application of flour-prepared soy milk، as emulsifier، and its influence on flow behavior and textural properties (firmness، adhesive force and adhesiveness) of mayonnaise were studied. Egg، as initial emulsifier، was substituted at replacement levels of 25، 50، 75 and 100% with soy milk and samples with pure yolk and whole egg were prepared as control experiments. Flow behavior of samples fitted with Power law، Herschel-Bulkley، Bingham and Casson models and all samples showed shear thinning behavior. Viscosity versus shear rate curve and evaluation of textural characteristics provided an evidence of high effectiveness of soy milk in emulsification. Therefore، as a general conclusion، soy milk has the potential to be used as an emulsifier and stabilizing agent in mayonnaise.

The numerous health effects of acorn are well documented. Acorn tree is abundant in many parts of Iran and is usually wasted or used as animal feed. With the aim of increasing food application of acorn، in this research، different levels of acorn flour (0، 10، 30، 40 and 50%، w/w، flour basis) were replaced with wheat flour in the production of Barbari bread. The farinograph results showed that with increasing the level of acorn flour، water absorption of the dough and dough softening decreased while dough stability time increased. Increasing the oat flour level reduced dough and bread final volume، increased the density، darkness and hardness of the bread. Determination of the crust color and crumb texture during three days of bread storage showed that the staling of the bread increased as the level of acorn flour increased. Inclusion of more than 30% acorn flour had negative effects on sensory characteristics of the bread. In total، to produce acorn Barbari bread، inclusion of less than 30% acorn flour is suggested.

Flaxseed is a good source of omega-3 fatty acid، lignin، dietary fibre and natural anti-oxidants such as tocopherols. Having benefits for health with preventing disease is the major reason for fortification of functional food products with flaxseed. In this study، the effect of incorporating flaxseed mealinto wheat flour in proportion of 0 (control sample)، 5، 10، 15 and 20% (flour basis) on chemical properties of bread and flour including oil content، fatty acids profile، tocopherols، acidity and peroxide and their changes during baking were investigated. Moreover، bread sensory characteristics upon 5 days of storage were determined. The results showed incorporating flaxseed up to 20% substitution with flour increased fat content، linolenic acid and tocopherols. During baking، acidity and peroxide values increased. Linolenic acid was stable upon cooking temperatures، however، tocopherols were decreased. Bread containing 15% flaxseed received higher sensory scores compared to other treatments، but over the time، bread sensorial quality was diminished upon storage of bread at room temperature.