مجله علوم و صنایع غذایی ایران
سال سیزدهم شماره 9 (پیاپی 58، آذر 1395)

Electrostatic interaction between proteins and negatively charged polysaccharides leads to formation of stable colloidal system or causes complex coacervation. Therefore, in this study phase behavior of the mixtures of 0.4% milk proteins (sodium caseinate or whey protein isolate) with soluble fraction of tragacanth (up to 1%) or soluble fraction of Persian gum (up to 2%) as a function of pH (2–7) was investigated, in order to obtain appropriate protein:polysaccharide ratio to formation of soluble complexes in a wide range of pH. According to the results, the mixtures of sodium caseinate–soluble fraction of Persian gum, sodium caseinate–soluble fraction of tragacanth, whey protein isolate–soluble fraction of Persian gum and whey protein isolate–soluble fraction of tragacanth were soluble complexes at the whole pH range at the ratio of 0.4:0.6, 0.4:0.6, 0.4:2 and 0.4:1, respectively. Moreover, it was found that enhancement of total biopolymer concentration (at a same ratio) had no effect on the phase behavior of complexes. In addition, evaluation of the phase behavior of the mixture of milk proteins–alcohol-insoluble fraction of soluble part of native gums illustrated that both alcohol-insoluble and soluble fractions probably have impact on stability of complexes at mentioned ratios.

One of the most important points for yogurt production is the selection of starter culture, and also because of the necessity to preserve our natural starter cultures and to increase the availability of them for industrial use, the aim of this project was to determine the technological and organoleptic properties of yogurts producted by starter culture isolated from Iranian native yogurts. Eleven different yogurt samples were produced using 5 Lactobasillus delbruekii subsp.bulgaricus and 2 Streptococcus thermophiles isolates. Results showed there were no significant differences between acidifying activity of EPS-producing and non-EPS-producing starter cultures. Also isolates with a high proteolytic activity (isolates used in the examples H and I that proteolytic activity reaches during 28 days to 1 unit) have less the ability to produce acid during storage and viability of these isolates had been more than other strains. Samples that produced by EPS-producing starter culture exhibited better texture properties (consistency, syneresis and water holding capacity) than samples that produced using NEPS-producing starter culture. However, H and I samples due to high proteolytic activity and type of the exopolysaccharide is produced had less desirable textural properties. Syneresis reduced during storage and water holding capacity increased. But the synersis and water holding capacity of the samples produced using starters with high proteolytic activity, such as samples E, H, I similar to other samples until day 21, and in the fourth week the trend of changes has was reversed and the amount of synersis increased and water holding capacity is reduced.

To investigate the causes of food waste in Zanjan city, 30 bakery stores were selected randomly and by going directly to them, the components of the formulation that make up the bread was collected containing samples of flour , yeast , yeast bread consumption production.
In this study the qualitative properties of yeast, the amount of bread waste, bread bakery shelf-life and moisture preservation were determined. Microbiological analysis were done on five types of flour, 6 types of yeast and 24 types of sourdough used in baking. Furthermore, consumption of soda was determined (in breads with a pH greater than 6.2) or its use in the production of bread as a yeast alternative.The qualitative features of yeast showed that the half of the yeast samples had not ability to produce enough gas which was an effective technological problem at Zanjan bakeries (6.9%).
Microbiological tests showed that the used yeast infected by E. coli but in the bread flour samples, the results comply with the standard. Microbial populations in different sourdough samples were very versatile and varied quantitatively with each other.
Studies showed that about 5 percent of bakeries have used of soda as an alternative to yeast. Amount of the bread wastes reached to 27/17 % which the 0.5 % owned soda consumption, 6.9% belonged to low quality yeast and 5.17 % was due to non-compliance with fermentation time. The shelf life of bread and moisture preservation in pita bread with a low pH level of 6.2 significantly were higher than breads with a pH greater than 2/6 respectively.So, due to the lower performance of yeast and lack of the needed time for properly fermentation, also the poor quality of processed breads with baking soda, it is recommended to use the healthy bakery yeast and sourdough with uniformity of microbial characteristics.

In biscuit production, sucrose is one of the major ingredients. Addition of sucrose is not only for the sweet taste it provides, but also for its positive effects on physical properties of the product. Since sucrose consumption is growing worldwide, finding an alternative sugar source other than sugar beet and sugar cane as the main sources of sucrose is necessary. In this research, sucrose was replaced with 0, 20, 40, 60, 80 and 100% (weight basis) of date syrup and date liquid sugar and the effects on rheological properties of biscuit dough were studied. The results from farinograph showed that the dough consistency and elasticity reduced with increasing the sucrose replacement level. However, no significant difference between the samples made with date liquid sugar and date syrup was not observed. The results of Texture Analyser showed that with reducing the sucrose content dough consistency, energy required for compression, springiness and cohesiveness reduced while adhesiveness increased. The values obtained for energy, consistency and adhesiveness of the samples containing date liquid sugar were higher than those of date syrup, while springiness was lower. Based on the results the maximum percentage of the sucrose replacement with date liquid sugar was 60% and with date syrup was 40%. At higher percentages the quality of the dough reduced considerably.

In this study, the effect of different concentrations of potassium sorbate and sodium benzoate (300 , 400, 500 ppm) on microbial characteristics (total count, mold and yeast) of dried sour cherry with moisture of 25 % was evaluated during 6 months storage at temperatures of 8, 22, 37 °C. Microbial characteristic of samples were evaluated in the 1th, 3th, 6th months. The results showed that the dried sour cherry which treated with potassium sorbate and sodium benzoate during the six months of storage in vacuum packages had no microbial spoilage. The results showed that by using sodium benzoate and potassium sorbate at optimum condition, the amount of mold and yeast decreased from 11.67×10 cfu/gr (in control dried sour cherry) to 3.67×10cfu/gr and 3.33×10 cfu/gr respectively. Also, by using sodium benzoate and potassium sorbate at optimum condition, the amount of total count decreased from 2.13×103 cfu/gr in control sample to 0.50×103 cfu/gr and 1.23×103 cfu/gr respectively. The amount of mold and yeast and total count were decreased by increasing concentrations of potassium sorbate and sodium benzoate. By increasing temperature (from 8 to 37°C ) and time(1 to 6th month) due to the decomposition of potassium sorbate and sodium benzoate, antimicrobial effects of these compounds significantly decreased (p

Listeria monocytogenes is one of the most dangerous bacteria in food products which caused about 20 to 30% fatalities. One of the major foods which caused listeriosis is ready to eat (RTE). So, appropriate heating processing methods are need for elimination of L. monocytogenes. These bacteria has ability entering into viable but nonculturable (VBNC) form in unfavorable conditions. So this investigation was aimed to considering behavior of this pathogen at higher temperatures from recommended for elimination of these bacteria. For this purpose, bacteria in 5×106 counts in mid log phase were inoculated into two medium BHI Broth and fish Broth (FB) and they exposed to 85 ºC for 10 minutes. Direct plate count on listeria choromogenic agar, BacLight® Live/Dead and gene expression of 16S rRNA, the housekeeping gene, were done before and after heat shock. The results show that these bacteria lose their culturability during high heat shock. The results of fluorescent dyes showed the viability of these bacteria after heat shock (p

In this study, the extract of Entromorpha intestinalis was exctracted using different solvents including water, chloroform, methanol, ethanol, hexane and acetone. Antibacterial and antifungal properties of these extracts were evaluated using a modified disk diffusion method. Microorganisms investigated in this research were included Gram-positive bacteria Lactococcus lactis, Listeria monocytogenes, Bacillus subtilis, Gram-negative bacteria Escherichia coli and fungi Candida albicans. According to the results, the methanol and hexane extracts of this alga had the best activity against L. lactic. (p

The aims of this study was improve the rheological charactristics of gelatin obtained from the skin of the Big head by rheological test. In this study gelatin was extracted from big head (Hypophtalmichthys nobilis) fish skin and the effect of microbial transglutaminase (MTGase) on gelatin in different concentrations (1, 3 and 6 u/g gelatin) and reaction times (15, 30 and 60 minutes) was examined. The result showed that addition of MTGase in minimum concentration and reaction time ( 1u/g gelatin in 15 minute reaction time) increase the gel strength from 228±1g to 250g significantly (p≤0.01) whitout the changing the color of result gelatin. Furthermore, increasing concentrations of MTGase redused the gel strength of gelatin. Also the addition of MTGase increased the viscosity in all shear rates and improved melting and gelling point. The increase in storage modulus (G') values with the addition of MTGase indicated the formation of firmer gels and also changes in G' and G" values during the heating and cooling sweep test showed increase in melting point and gelling point. It is conclude that the application of 1-6 U/g of MTase can improve the quality of driven gelatin from big head fish.

Short and medium infrared radiation implemented as an energy source in drying process under vacuum conditions. Any comparative study was not carried out between these two energy sources in drying process of agricultural products. In this study, effects of short and medium wave of infrared were evaluated and compared on drying behavior of peach slices under vacuum condition. Drying of the samples was implemented under both the energy sources at the absolute pressures of 20, 40 and 60 kPa and drying temperatures of 50, 60 and 70°C. Drying behavior of peach slices as well as the effect of drying conditions on moisture loss trend, effective diffusion coefficient, color and shrinkage of peach slices, dried in an infrared-vacuum dryer were examined. Effective diffusion coefficient of peach slices under medium wave infrared at different drying conditions was more than short wave infrared in the ranges of 2.6×10-11 to 1.4×10-10 m2/s. Total color difference and shrinkage of peach slices under short wave infrared at different drying conditions was less than medium wave infrared in the range of 6.6 to 8.7 and 7.8% to 9.7%, respectively. Minimum total color difference of peach slices under short and medium wave of infrared were obtained 8.2 and 14.8 and minimum shrinkage of peach slices under short and medium wave infrared were achieved 46.7% and 55.9% respectively.

In this study the effect of Leidium perfoliatum seed (LPSG) and xanthan gums on rheological properties of dough and quality of pan bread was investigated. Results showed that with increasing xanthan and LPSG, water absorption, dough stability and viscosity increased. However, mixing tolerance index and gelatinisation temperature decreased with increasing gums concentration. Adding LPSG and xanthan gum had no significant effect on dough development time. The gas retention remained constant with addition of LPSG. However, increasing xanthan gum up to 0.5% increased the gas retention capability of dough. Increasing the concentration of gums also increased the porosity, moisture and L*, but specific volume and cell size were reduced. Based on these results, LPSG functions like xanthan, thus can be used as a proper hydrocolloid for pan bread.

Increasing soy protein isolate content may be a practical and cost-effective means to control the functional properties of imitation pizza cheese. Imitation cheeses containing 2, 3 and 5% (w/w) soy protein isolate as a partial caseinate substitute were manufactured and dynamic rheology of these products were compared to a control (0% w/w soy protein isolate) in temperature sweep analysis. The dynamic rheological properties of caseinate-based imitation cheeses containing various concentrations of soy protein isolate were investigated using a strain-controlled rheometer. The storage modulus (G’), the loss modulus (G”) and the loss angle (Tan) were measured as a function of temperature (35–100°C). The storage modulus and loss modulus of imitation cheeses was significantly decreased (P0.05) at all examined temperatures (35–100) with the inclusion of soy protein isolate. Inclusion of soy protein isolate significantly increased imitation cheese peak Tan values compared to control (P0.05), and the inclusion of 5% (w/w) soy protein isolate as a partial caseinate substitute had the greatest effect. In sensory evaluation, in terms of texture and mouthfeel, flavour and total acceptance the highest score belonged to control, while in all of samples lowest score observed in sample containing 5% w/w soy protein isolate. The results of this study showed that varying the level of soy protein isolate altered dynamic rheological properties as a function of temperature and thus the functionality (for example, meltability), as well as sensory attributes of imitation pizza cheeses.

Chemical modification of starch is of the prevalent used methods in order to improve its physicochemical attributes. In this study phosphorylated and hydroxypropylated wheat starches were produced with 0.096 and 2.106% degree of substitution, respectively; and then some of their physicochemical and rheological attributes were studied. The implemented chemical changes due to hydroxypropylation and phosphorylation on native wheat starch were exhibited by FT-IR. X-ray diffraction (XRD) results showed that the native and phosphorylated wheat starches had the most and least amount of crystallinity with 17.34 and 16.14%, respectively. The influence of temperature on swelling power revealed that the native (Ea=46.111) and hydroxypropylated (Ea=26.603) wheat starches had the most and least thermal sensitivity, respectively. Besides, in the case of solubility index, it was observed that native (Ea=77.674) and phosphorylated (Ea=44.478) starches had the most and least thermal sensitivity, in the order given. The high value of determination coefficient (0.895-0.979) attained from the modeling results of the solubility changes with temperature using two power law equations, demonstrated the high capability of these models in prediction. It was seen that hydroxypropylation and phosphorylation of wheat starch resulted in 2.65 times increase and 17.58 times decrease in paste clarity compared to native starch (p

The objective of this research was to investigate the feasibility of edible film made from salep in which the hydrophobicity of film was modified by using stearic acid as a lipid agent. In addition its mechanical, thermal, permeability and color changes of film were analyzed. For this purpose, edible composite films were prepared from salep, stearic acid, and tween 80 in emulsion form using an ultra turax apparatus. The water vapor permeability (WVP) of the emulsified films was reduced by fatty acid addition. Also the permeability to oxygen of the emulsified films was lower than that of a salep film without fatty acid, but the difference was not significant in higher concentration of stearic acid. Scanning electron microscopy (SEM) was also used in order to analyze films microstructure. Finally, differential scanning calorimetry showed that the glass transition temperature (Tg) of the salep film was 12 °C and was considerably affected by stearic acid concentration.

For the first time in case of fraud detection in Iran, the amount of water as a fraud in natural lime juice was detected using fuzzy modeling system in the present study. Four parameters consisting pH, EC (electrical conductivity), contrast and homogeneity (obtained from the samples’ images) were considered as input and the amount of water in natural lime juice was introduced as output of the fuzzy model system. Zero, 5, 10, 15, 25, 30 and 40% of water were used for system training and 7.5, 12.5, 20 and 35 % were used for testing the system. Mamdani’s fuzzy inference system, triangle membership functions and 7 rules were used for fuzzy modeling. The performance of the model was determined using R2 and RMSE statistical parameters. As a result, high value of R2(0.99) as well as low value of RMSE (1.67) demonstrated that fuzzy inference system can be used as an efficient method to estimate the amount of water fraud in natural lime juice.

Molten dark chocolate is a dispersion of solid particles including sugar and cocoa powder in a continuous phase of cocoa butter. Hence, the rheological properties as well as the particle size distribution of ingredients in chocolate are very important for obtaining high-quality products with well-defined texture. Therefore, the present study aimed to evaluate the effects of sugar substitutes on rheological characteristics and particle size distribution of prebiotic dark chocolate. For doing this, a prebiotic compound (inulin) in combination with bulking agents (polydextrose and maltodextrin) at different levels (0–100 %) along with sucralose were used. Based on our findings, all the treateded samples showed thixotropic and pseudoplastic behavior and the Casson mathematical model most closely fitted to the rheological data. Furthermore, the sucrose replacement slightly affected the viscoelastic properties and the viscosity of the samples was time independent. In terms of the particle size, they were somewhat larger than the commercial one but still below the taste threshold.

Use of soy products in sesame cream composition led to produce nutritious and healthy product with better quality and quantity. In this study, the effect of replacing soy meal instead of sesame in producing sesame cream to reduce fat and increase the protein content and the use of lecithin as emulsifier to improve rubbibility on chemical, physical properties and sensory evaluation was examined. Replacement percent of soy meal (0, 20, 30 and 40 percent) and lecithin (7,5,0 and 10 % w/w) was considered in the formulation. By increasing soya meal and lecithin replacements, changes in fat, protein, hardness, color (l *, b *, a *) was significant. In soy meal replacing, significant moisture difference( p

Mallow (Malva neglecta) is grown in Middle East countries. In herbal medicines mallow is used as pain decreasing, importing injuries and removing gastrointestinal problems, respiratory system and so on. These specifications are dependent on structural components and plant mucilage respectively. In this study structural components and amount of leaves and stems mucilage was analyzed.In spring, leaves with stems were collected, dried and powdered. Quantity of protein, fat, ash, fatty acids and sterols were analyzed by AOAC and Iranian Standard methods. Mucilage of M.neglecta was extracted by deionized water in 90OC and extracted mucilage was dried in 50OC oven. Phenol-sulfuric acid method was used to determination of total carbohydrate. Leaves and petioles of M.neglecta are rich in protein and ash.40% of fatty acids is linolenic acid and more than 50% of total fatty acids are unsaturated fatty acids. Extracted mucilage was totally 12% in dry matter of plant. Total carbohydrate of M.neglecta mucilage was % 75.97±2.46 respectively. Having useful ingredients like zinc, copper, iron, protein, unsaturated fatty acid and high amount of mucilage demonstrates worth of M.neglectain food and medicines. Phenol sulfuric acid method was used in different temperatures from environment till boiling temperatures. Also using phenol-sulfuric acid method in boiling temperature was done before but in combination by autoclave instrument for getting total carbohydrates of M.neglecta mucilage is the first action.