فصلنامه پژوهش های صنایع غذایی
سال بیست و سوم شماره 4 (زمستان 1392)

Bifidogenic prebiotics fructans contain inulin, oligofructose and fructooligosaccharides. The aim of this study was to evaluate in vitro effectiveness, short chain β-fructans extracted from Salsify root (SCSF). Effect of SCSF on growth and activity of Bifidobacterium bifidum and E.coli was evaluated in concentrations of 0.5, 1, 2, 3% (w/v) during the 48 hours incubation period and it was compared with commercial inulin (HP-inulin). The results indicated that utilization of β(2→1) fructans by Bifidobacterium bifidum depended on the DP of fructo-oligomeric chains and these bacteria significantly utilized SCSF with short chain (lower DP) better than HP-inulin with higher DP (p<0.05). Also, in the case of both bacteria growth, no differences were observed between medium containing 2% and 3% (w/v) HP-inulin and medium without HP-inulin (p>0.05). Therefore, it can be concluded that HP-inulin at concentrations 2% and 3% (w/v) was not fermented by these bacteria, whereas supplementation with 0.5% and 1% (w/v) HP-inulin was found to be effective on bacteria growth (p<0.05). Also, the effects of SCSF (2% w/v) in growing of Bifidobacterium bifidum were significantly higher than that for Escherichia coli (p<0.05).

Large quantities of rice bran are generated as by-products during the milling of rice in Iran. Although the rice bran protein has high quality and usability in food industry but rice bran is used less now. For better use of rice bran protein, it is desirable to develop effective methods to separate or concentrate the protein component from this by product. In this investigation, with using of 1 N NaOH and in alkaline condition the rice bran protein concentrate was prepared by extraction of rice bran protein. Proximate composition, amino acid profile, and functional properties including water solubility, foam capacity and foam stability, emulsifying properties, water and oil absorption of rice bran protein concentrate were determined. The protein concentrate yield was 75%. The results of amino acid composition analysis showed that the lysine content, at 2.25%, and methionine content, at 2.17, of rice bran protein concentrate were lower than other amino acids. Water and oil absorption of rice bran protein concentrate were 2.01(g water/g protein) and 2.09 (g oil/g protein), respectively. Rice bran protein concentrate showed good emulsifying properties. Foam capacity was good in rice bran protein concentrate (P<0.05) but foam stability had decreased after 60 min until 60%. In conclusion, the amino acid composition and functional properties of rice bran protein concentrate was showed that this value-added product could be used as protein ingredient in livestock and aquaculture feed industry.

The quality of fried potato strips usually depends on color, flavor, texture and oil content. Frying is one of the most important stages in processing of this product. In order to investigate the kinetic of oil uptake, water loss and textural changes during frying, the potato strips with a cross-section of 0.8×0.8×8 cm were fried in hot oil at temperatures of 160, 175, 190 ℃ for 15 minutes after being blanched for 10 minutes at 70℃ and then pre-dried at 70℃ with air velocity of 1 𝑚⁄𝑠 until mean moisture content of 75% (wet basis). The results showed that increasing the temperature of frying increased the oil uptake and water loss from strips significantly (P<0.01). Increasing the frying temperature also decreased the core firmness and intensified the crust hardening. The different kinetic models were studied to describe the oil uptake, water loss and firmness changes of crust and core regions. The results showed that the first order kinetic with production rate limiting effect had the most conformity with experimental data of oil uptake and water loss.

Drying is one of the old methods used for preserving foods; however, due to possible occurrence of some undesirable changes in dried foods, its control is specifically important. Response surface methodology (RSM) is set of techniques used for controlling and optimizing processes where a desired surface is affected by many variables. Thus, RSM can be one of the appropriate methods for controlling time and various drying conditions. In this study, thin-layer drying of banana was conducted at four temperatures (50, 60, 70 and 80°C), three inlet air velocities (0.5, 1 and 1.5 m/s) and three banana thicknesses (2, 4 and 6 mm). The results showed that the highest desirability (0.91) in order to minimize moisture content and maximize drying rate achieved at 80°C temperature, 1.5 m/s inlet air velocity, 100 min drying time and 2 mm thickness.

White cheek shark (Carcharhinus dussumieri) is an important species shark fish in Persian Gulf. Because of high urea content in shark meat, there is a weak market for its fillet or other direct products in Iran. In this study, the effect of enzymatic hydrolysis by Neutrase on degree of hydrolysis (DH), nitrogen recovery (NR) and peptide chain length (PCL) of white cheek shark meat has been studied. Enzyme to substrate ratio of 12 AU/Kg proteins at 50oC has been applied for enzymatic hydrolysis. Degree of hydrolysis were determined during 10, 20 and 30 minutes. DH, and NR decreased, but PCL increased in each stage compared with the previous one. However, the mean of DH in the whole process of 10, 20 and 30 minute were 2.90, 3.79, 4.48% for DH, 74.79, 80.75, 89.64% for NR, and 51.54, 39.68, 33.98 for PCL, respectively. However, at longer hydrolysis time, DH, and NR increased, but PCL decreased significantly (P< 0.05).

The effect of heat treatment on shelf life and quality attributes of table grape (Vitis vinifera cv.bidaneh Sefid) during storage was studied. Table grapes were treated with hot water (22 °C as a control, 45, 50 and 55°C) for 1 min and stored at 1±0.5°C with 90-95% RH for 30 days (p<0.05). Fruit quality attributes including weight loss, marketability, pH, total soluble solids (TSS), total phenolics content and polyphenol oxidase activities were studied during cold storage at 15 day intervals. Postharvest treatment of fruit with hot water of 55°C retained fruit quality during storage. Hot water of 55°C retained berry weight, marketability and phenolics content and decreased the rate of increase in pH and polyphenol oxidase activity in grape samples. The results showed that heat treatment as an appropriate nonchemical method can improve the quality and shelf life of table grapes.

Glycyrrhiza glabra roots contain a compound that is called glycyrrhizin extensively used as natural sweeteners in food products and several pharmaceutical formulations. The main objectives of this study were identification of Glycyrrhiza varieties in Ardabil province (Korayim region) and determination of glycyrrhizin content in root and leaf of identified varieties. Moreover, determination of some chemical compounds in leaf of Glycyrrhiza varieties was performed. Glycyrrhizin content in root and leaf of identified varieties were detected by HPLC. Some chemical compounds in leaf of Glycyrrhiza varieties such as extracted fat, crude protein, ash, fiber and carbohydrate were analysed. Two varieties of Glycyrrhiza glabra L. were identified in Ardabil. The scientific names of these varieties were Glycyrrhiza glabra L.var. glandulifera, and Glycyrrhiza glabra L.var. glabra. Results of glycyrrhizin contents (based on dry matter) showed that glycyrrhizin content in roots of var. glandulifera and var. glabra was %4.34 and %3.29, respectively which were significantly (P<0.01) different with each other. At the both varieties, the highest content of glycyrrhizin was found in the root hull. The glycyrrhizin content of leaf in var. glandulifera and var. glabra was %0.072 and %0.085, respectively with no significant difference between varieties. Moreover, there was no significant difference between leaves of two varieties in measured chemical compounds, but between two stage of early bloom and late bloom, there were significant (P<0.01) difference between leaves of two varieties in measured chemical compounds (except of ash). In conclusion, the obtained results showed possibility of glycyrrhizin extraction in the root of var. glandulifera in comparison to var. glabra and it's use in food and drug products.

In this study, the antioxidant effects of different concentrations of Zataria multiflora (ZM) and Mentha longifolia (ML) essential oils (EOs) on ground chicken meat at 4 °C were investigated. Ground meat samples were subjected to five treatments: Control (with no EO), ML0.5 (Mentha longifolia EO 0.5% v/w), ML1 (Mentha longifolia EO 1% v/w), ZM0.25 (Zataria multiflora EO 0.25% v/w) and ZM0.5 (Zataria multiflora EO 0.5% v/w). Subsequently, samples were stored at 4°C and the antioxidant activity of EOs was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), reducing power, metmyoglobin and thiobarbituric acid (TBA) assays at 1, 4, 7 and 10 days. In DPPH assay, antiradical activity was significantly increased in meat samples with the addition of both ML and ZM, but ZM0.5 showed the highest radical scavenging activity. When reducing power assay was used, only ZM0.5 demonstrated significant effect. ZM0.5, to a lesser extent, ML1 inhibited metmyoglubin production in meat samples. The results of TBA assay showed that the all EOs treatments significantly reduced the lipid oxidation. The results of this study showed the use of ZM and ML essential oils in chicken meat can delay the chemical spoilage process.

Analogues cheese production using cheaper food sources such as vegetable proteins and oils has been studied in recent years. Nowadays, ultrafiltered white cheese is assumed as the most important industrial cheese in Iran. In this work, analogues of this cheese have been made by substituting 1/3 and 2/3 of the dairy fat with margarine. Physical–chemical composition, fatty acids profiles, texture and sensory acceptance were determined in the samples. A random block experimental design was adopted. Results showed that replacement of milk fat by margarine caused changes in fatty acid profile with increasing the ratio of unsaturated to saturated fatty acids which can lead to favorite nutritional effects. Furthermore, using of margarine increased of stiffness and could overcome to texture softening as one of the main defects of UF white cheeses. Sensorial characteristics of analogue cheeses were similar to control samples with respect to color but better than control samples in stiffness, while overall acceptance of analogues with 1/3 fat replacement was similar to control sample and better than analogue cheeses with 2/3 fat replacement.

Phase separation is the main problem encountered in doogh during storage due to its low pH and aggregation of caseins. It is of interest for researchers and industry to prepare a doogh that does not undergo serum separation and suspends the infused herb particles within for a long period of time. Xanthan as the fluid gel-forming agent was used in combination with denatured whey protein, pectin and locust bean gum to stabilize mint-containing doogh samples. Flow behavior studies revealed that xanthan provided a yield stress to the drink demonstrating the typical behavior of fluid gels. Yield stress was calculated by extrapolation of the flow curves using Herschel-Bulkley model.Mint stability was predicted by considering the overall balance of forces acting on the particles. Denatured whey protein, locust been gum and pectin in the mixture of xanthan gum, increased viscosity and particle size and reduced serum separation. Mint particles sedimentation was totally suppressed by a combination of xanthan, denatured whey protein and pectin during storage of doogh for 40 days.

The effect of zedo gum (with concentrations of 0, 0. 2 and 0. 4 %) on qualitative properties of doogh made from yoghurt diluted by UF milk permeate (at levels of 0, 25 and 50 %) as replacement of water was studied during storage for one month at 4ºC using response surface methodology and face centered design. The results showed that serum separation decreased with increasing the levels of permeate and zedo gum and it increased during storage (p<0. 05). Apparent viscosity also increased with increasing the levels of permeate and zedo gum, but it's changes during storage was not significant (p>0. 05). Acidity was considerably affected by permeate, zedo gum content and storage time. Both permeate and zedo gum resulted in lower moisture content, for increasing the dry matter and absorbing water, respectively. Density was increased only by permeate. According to the results obtained from color analysis, L* value increased during storage time but it decreased under the interaction of permeate and zedo gum. At lower levels of zedo gum, the increase of permeate caused a lower a* value. However higher levels of zedo gum resulted in a higher a* value. Both permeate and zedo gum resulted in b* value improvement. The results of sensory analysiاs showed that permeate caused the score of flavor decrease and zedo gum caused the score of consistency increase during storage. The amounts of 0. 19% zedo gum, 32. 55% permeate and 30 days storage were obtained as optimum conditions.

Contamination by heavy metals is one of the major environmental problems and food safety concerns. Rice, especially white rice (Oryza sativa), is the most basic food in the diet of different individuals including Asian countries and the second most consumed food among Iranian peoples. The aim of the present study was to control and determine cadmium, lead and arsenic concentrations in the most consumed rice (Oryza sativa) verities in Tabriz (East Azerbaijan Province). For this purpose, 10 samples of the most consumed imported rice were purchased randomly from Tabriz bazaar and after preparation, evaluation of cadmium, lead and arsenic concentrations were performed by PG-900 Atomic Absorption Spectrophotometer in specific wavelengths and Arsenometer. After gathering information, data were analyzed using SAS statistical software and compared with national standards. A significant difference was observed between heavy metals contamination in rice samples (P<0.01). Results indicated that the mean concentrations of cadmium, lead and arsenic in rice samples were 0.109±0.157, 0.290±0.154 and 0.55±0.028 mg/kg dry basis, respectively. The mean concentrations of cadmium and lead in rice samples were noticeably higher than criteria of Institute of Standards and Industrial Research organization of Iran. For assay the safety of dietary intake, weekly intake of heavy metals by rice was calculated based on the intake of a typical Iranian person (whereas daily intake of rice is 165 g/person/day and average body weight is 60 kg/person). Results revealed that weekly heavy metal intake from rice did not exceed the provisional maximum weekly intake recommended by WHO/FAO.