JOURNAL OF FOOD RESEARCH (UNIVERSITY OF TABRIZ)
Year:2018 | Volume:28 | Issue:1|Papers Count:15

Whey separation is a common problem in production and storage of acidified milk drinks (AMDs) which is due to the casein instability and sedimentation at low pH (4. 6≤ ). To prevent or reduce protein aggregation, different stabilizers are used. Milk-barberry juice drink can be one of the functional products with high nutritional value. However, owning to low pH in barberry juice, protein sedimenitation is a problem in these products. In this study, pectin, carboxymethyl cellulose (CMC) and the mixture of them (at 50: 50 ratio) at concentrations of 0. 2, 0. 4, 0. 6 % w/w were used to improve stability of milk-barberry juice drink. In treatments, the parameters of viscosity, sedimentation and whey separation were determined after two-week strorage. The findings showed that pectin 0. 2, pectin 0. 4% were the most effective stabilizers, respectively. After that, the optimal formulation of milk-barberry juice drink prepared and stored at refrigerated for 42 days and its physicochemical properties were investigated. The results showed that the effect of milk, barberry juice and pectin content were significant (p<0. 05) on product sedimentation and sepration. During storage, the amount of antocyanins and phenolics increased from 69. 73 to 70. 93 mg cyanidin 3-glucoside and from 1847. 85 to 2512. 35 mg galic acid per liter, respectively in the drink containing 0. 2% pectin. The results showed that production of milk-barberry juice drink with the lowest sedimantation and whey separation could be possible using pectin as stabilizer.

Inulinase with high thermal stability is preferred to hydrolyze inulin and produce high fructose syrup to increase the rate of conversion, prevent microbial contamination and make inulin more soluble. The aim of this study was to evaluate the structural and functional characteristics of endo inulinase after modification with PLP. To determine the thermal stability, the residual activities of the endo inulinase before and after modification with PLP was measured after 130-minute incubation at 25-65° C while, their activities were measured daily to estimate the shelf stability. Circular Dichroism, absorbance in 280 nm, extrinsic and intrinsic fluorescence were carried out to assay the structural changes and the secondary and territory structure of the endo inulinase before and after modification with PLP. Chromatograms of inulin hydrolysis products were plotted after hydrolysis with either native or PLP modified endo-inulinase using HPLC and the catalytic parameters of both enzymes were calculated. α-helix content increased after modification with PLP. The results of assaying the territory structure including UV-vis and fluorescence emissions confirmed the improved thermal stability of endo inulinase after PLP modification. The results of the shelf stability proved the reduced activity loss of PLP modified inulinase, compared to the native one. Efficiency improvement of PLP modified inulinase for inulin hydrolysis was demonstrated by HPLC. After enzyme modification, Vmax increased and Km decreased which proves the improved efficiency of the PLP modified enzyme.

To investigate the effect of replacing dried mushroom on viscoelastic properties of sponge cake, stress relaxation test was done. Mushrooms were dried in optimal conditions, and then mushroom powder was used for enrichment of sponge cake at four levels of 0, 5, 10 and 15 % as substitute of wheat flour in the formulation. After preparing the samples, stress relaxation test was done by a texture analyzer in storage time and coefficients of the Peleg-Normand and the extended Maxwell models were calculated. The results showed that with increasing substitution of mushroom powder initial force and balance force values were decreased. During storage time of cake, initial force and balance force values were increased. The parameters of Peleg-Normand model include k1 and k2 decreased with time that indicating a reduced elasticity of the cake with the passage of time. The cakes show solid viscoelastic behavior and by increasing replacement, total reduced forces (F1+F2+F3) of generalized Maxwell model decreased that reflects the increasing of elasticity. The results of stress relaxation modeling of experimental data by Peleg-Normand and the extended Maxwell models showed that the Maxwell model has more efficient to evaluation of viscoelastic properties of rich sponge cake with mushrooms powder.

Nitrite and nitrate salts are used in meat products as preservative against growth of dangerous bacteria such as Clostridium botulinum, delaying meat corruption and color fixative. The use of these additives, increases risk of carcinogenic nitrosamine production and carcinogenicity. Hence, the use of these additives should be according approved standard (maximum 120 ppm for nitrite). This descriptive, analytic study was designed to measure nitrite content in different types of meat products marketed in Tabriz in 1394, based on random sampling. A total 90 samples of different kinds of meat products samples produced in 6 factories East Azerbaijan (60 samples) or other provinces (30 samples) was collected according national standard No. 690 about meat product sampling. The amount of nitrite in the meat products was measured according to Iranian national standard No. 2303 with spectrophotometry method. The products analyzed until 4th days after production for East Azerbaijan products and less than 30 days in the cases of other provinces products. The result of this experiment showed that the residual concentrations of nitrite were between 3. 3-94. 9 ppm in two kinds of sausage that was less than approved national maximum residual limits. According to one way ANOVA test the differences between the nitrite residues in sausage with different meat content were not significance (P>0. 05). However, this study showed that nitrite residues decreased in meat products according time of production significantly (P< 0. 0001).

Biosurfactants are amphiphilic molecules that produced by microorganisms and have both hydrophilic and hydrophobic moieties. Scant information regarding their toxicity, combined with high production cost seem to be the major barrier for the limited uses of biosurfactants in the food area. In this work, Lactobacillus plantarum subsp. plantarum PTCC 1896 )probiotic( was used for biosurfactant production in MRS medium. Also, in order to reduce the production cost of biosurfactant, four abundant and low cost lignocellolosic wastes, including rice and wheat bran and straw were evaluated. The biosurfactant produced using rice bran hydrolysate exhibited the minimal surface tension (23. 74 mN/m) as compared to other produced biosurfactants and it was selected for further studies. The biosurfactants produced in MRS and rice bran hydrolysate media were extracted, purified and characterized. Biochemical and FTIR spectroscopy analysis showed the biosurfactants are structurally different polysaccharide-protein complexes. These results could provide incentives for the industrial production of the low cost and safe biosurfactant, which seems to offer potential applications in the food and medical industries.

Kashk, which is a traditional dairy product in Iran, is produced as limited due to unsuitable hygienic conditions and long drying period. It can be produced as standard and safe with transferring from traditional to industrial production scale. In this study, Kashk was produced in two drying methods: sun drying and hot air drying at 50, 60 and 70° C temperatures. After drying, the amount of dry matter, protein, fat, ash, salt, acidity, pH, aw, water absorption, total microbial count, coliform, mold and yeast, color parameters including L*, a*, b*, H, C and Δ E, and hardness in samples were measured. Results showed that there was no significant difference in protein, fat, ash, and salt content of Kashks (p>0. 05). Maximum acidity and minimum pH were seen in sundried Kashks. In the hot air method, with increasing temperature acidity and hardness increased and pH and water absorption decreased. Microbiological analysis showed the highest total microbial count in samples dried at 50° C and the lowest count in Kasks dried at 60 and 70 ° C. The lowest Δ E was found in both of samples dried at 60° C and sundried. Similarly, sensory evaluation showed the highest overall acceptance in samples dried at 60° C and sundried. According to the result of this study, temperature of 60° C is recommended for drying of Kashk.

Anthocyanins are very useful and they can be considered as a proper option for using as a food dye in production of various foods due to the wide range of colors and antioxidant properties. In this study, the effect of parameters such as solvent (acidic ethanol with Hcl 1. 5N, ETHANOL 80%), solvent/solid ratio (10, 15, 20), temperature (30, 40, 50), time and (dark/light) on anthocyanin extraction from the peel of red onion and red cabbage were investigated using solvent method. FFD model was used to determine the optimum extraction conditions. The results indicate that the maximum amount of extraction from the peel of red onion and red cabbage are respectively in operating conditions such as acidic ethanol with HCL 1. 5 normal (15: 85), 80% ethanol and temperate of 31. 58, 35. 88 ° c and the time of 18. 32, 3. 4 hours, and the solvent/solid ratio equal to 18. 65, 18. 04 (volume/mass) in a dark environment. In order to increase the stability of produced liquid color against environmental factors, microencapsulation was done through freeze drying method with Arabic gum and maltodextrin. According to the results of TGA test and DSC tests, Arabic gum has more resistance against the heat so that the initial decomposition temperature of encapsulated powders with this coating material for the peel of red onion and red cabbage are increased from 63. 82 to 250. 87 centigrade degree and from 81. 03 to 263. 64 centigrade degree respectively. The average of particle size of encapsulated powders are smaller with maltodextrin and equal to 6. 1 and 21. 5 micrometers respectively. X-ray diffraction indicates that the structure of encapsulated powder is amorphous.

Plum as a fruit is used in fresh market or processed form. This research was conducted to evaluate the effect of pre-harvest application of methyl jasmonate on qualitative characteristics and shelf life of plum cv" Gold Drop". Experiment was carried out as a factorial based on randomized complete blocks design with four replications. Treatments were included in five levels of methyl jasmonate (0, 5. 0, 1, 5. 1, 2 mM) that were used as spray on selected branches of trees. After harvesting, fruits were stored at 2 ° C and 95% relative humidity for 6 weeks. The qualitative characteristics including firmness, soluble solids, titratable acidity, vitamin C, total phenol-and flavonoid, total antioxidant activity and pH of fruit juice were measured every week. The results showed that methyl jasmonate had significant effects on qualitative traits and shelf life of fruits. The pH of fruit juice in treated fruits were less than control and the amount of soluble solids, firmness, titratable acidity, vitamin C, total phenol-and flavonoid and antioxidant activity in treated fruits were more than control fruits. Methyl jasmonate at 2 mM concentration were resulted in better preservation vitamin C, soluble solids, pH, firmness, phenol, flavonoid and antioxidant activity was compared to other concentrations.

This study was aimed to investigate substitution of nitrite in sausages formulation. For this purpose, sausage samples were produced using 60 ppm nitrite combined with a mixture of red beet powder and rosemary essential oil in the form of four treatments including: T1 (1. 5% beet + 0. 02% rosemary), T2 (1. 5% beet + 0. 04% rosemary), T3 (3% beet + 0. 02% rosemary) and T4 (3% beet + 0. 04% rosemary) and control sample produced by 120 ppm nitrite (without beet powder and rosemary essential oil). All samples stored in the refrigerator for 35 days and physicochemical, microbiological and sensory properties were evaluated. The results showed that thiobarbituric acid and peroxide values in control sample had the highest amounts of 0. 16-0. 65 and 0. 36-1. 37, respectively, during the study, but the lowest values were related to T4 by amounts of 0. 06-0. 39 and 0. 13-0. 92, respectively (P<0. 01). Also the highest amount of pH and a* color index were belong to T4 and the lowest values to the control sample. In microbial tests, all samples had total bacterial counts less than 3. 6 log cfu/g and significant difference were not observed between control and treatments. Moreover, Clostridium perfringens was not detected in any of the treatments and coliforms was not enumerated in treatments (except control). Also, molds and yeasts were enumerated only in control, T1, and T2 samples at 28 and 35 days of storage. Sensory evaluations mostly showed no significant difference between treatments and control sample (P>0. 01). Generally, the results indicated the possibility of partial replacement of nitrite using a combination of rosemary essential oil and red beet powder.

Cinnamon primarily contains several phenolic compounds and its health and therapeutic effects has been proved. To produce functional product and renewed interest in milk consumption, honey milk formulations containing cinnamon (0. 1, 0. 4 and 0. 7%), guar and kappa-carrageenan (0, 0. 05 and 0. 1%) have been studied in current research. Statistical analyze has been performed through Design Expert software and surface response methodology with Box-Behnken design. Physico-chemical properties such as pH, acidity, viscosity and sedimentation rate moreover nutritional value through radical scavenging activity (DPPH) have been evaluated. Antibacterial effect of cinnamon has been surveyed through total bacterial count and sensory properties analyzed using 5-point hedonic scale. The results showed that adding cinnamon to formula, improved the anti-oxidative properties without any side-effect on pH and acidity but at higher concentrations, sensory attributes associated with sandiness. Furthermore, with increasing amount of cinnamon in the samples, the bacterial population was reduced significantly. The use of guar and kappa-carrageenan gums significantly reduced sedimentation rate and increased sensory acceptability. The results of optimization showed that using cinnamon at 0. 43%, guar gum 0. 09% and kappa-carrageenan 0. 08%, functional product formulation with high stability, extended shelf life and overall acceptability, is feasible.

The effects of pomegranate peel extract (PPE) on microbiological parameters and lipid oxidation were investigated in beef burger stored for 6 days at 4° C. Beef burger was treated with PPE at 500, 1000 and 1500 mg/kg of extract powder and the results were compared to beef burger without any additive (ControlN) and beef burger with 200 mg/kg BHT (ControlP). The instrumental color (CIE L*, a*, b*), total bacterial count (TBC) and 2-thiobarbituric acid reactive substances (TBARS) were determined at a gap of 3 days interval for a period of 6 days. PPE significantly (p<0. 05) reduced the loss of redness and the increase of lightness during storage of ground beef, whereas increased yellowness of ground beef compared to ControlN. In addition, TBARS value and TBC significantly were decreased in samples containing 1000 and 1500 mg/kg of extract powder than the ControlN. Sensory evaluation results also showed that PPE had no significant effect on overall acceptance of beef burgers. The present results highlight the potential usage of pomegranate peel extract as a natural antioxidant and antimicrobial in ground beef during chilled storage.

The aim of this study was to evaluate the effect of marinade solution with different acetic acid concentration (، 00. 5, 1 and 1. 5% w/w)-sodium chloride (2%) and immersion time (، 024, 48 and 72h) on physicochemical and quality characteristics of biceps femoris (BF) muscle of Iranian camel. For this purpose, pH, moisture content, marinade uptake, color properties, water-holding capacity, pigment oxidation indicators and thiobarbituric acid were examined. Results showed that the acetic acid concentration and immersion time of the samples had significant effect on the marinade uptake, moisture content, water holding capacity (WHC), cooking loss, myoglobin, brightness (L*) and redness (a*) properties. The immersion time significantly affected thiobarbituric acid of the samples, whereas marinade concentration had not significant impact on it. The pH of marinated meat exhibited a direct relationship with WHC, myoglobin and a*, but a reverse relationship with cooking loss, thiobarbituric acid and Met-myoglobin properties. Overall, the results indicated that the combination of acetic acid and sodium chloride marinade could be a useful method for improvement the quality of camel BF muscle.

The aim of this study was to investigate the effect of process conditions as well as ultrasound and microwave pretreatments on oil uptake during frying of potato slices. In this study, ultrasound pretreatment with two frequencies of 28 and 40 kHz and microwave pretreatment with two powers of 3 and 6 watts per gram was applied to the potato pieces. Then, the frying process was done at 150, 170 and 190° C for 1, 2, 3 and 4 min. The results showed that oil uptake is decreased or increased using the ultrasonic pretreatment depending on the process time and temperature. Oil uptake was reduced at the beginning of the process with low temperatures but was increased at the end of the process with high temperatures compared to controls. In addition, Microwave pretreatment significantly reduced oil uptake of the potato slices. Oil uptake was further reduced by increasing microwave power from 3 to 6 watts per gram. In addition, for predicting oil uptake with regard to the process conditions, six models including 2 models from the literature and 4 new models proposed in this study was examined. Considering the results of the fitted experimental data, ultrasound and microwave pretreatment increased and decreased the equilibrium oil content, respectively. Also, the ultrasound pretreatment reduced the oil uptake rate constant, but the microwave pretreatment increased it.

Milk is one of the most consumed dairy products that have great nutritional value. This valuable product has specific physicochemical properties that should be evaluated when delivered to dairy plants. Nowadays, some of the owners of dairy industry do not pay much attention to health aspects and quality of milk and they only evaluate the indicators such as fat level to pay the cost to farmers. But the raw milk quality can be more precisely controlled by evaluation of total microbial count and physicochemical characteristics of milk. In this study, some physicochemical and microbial properties of raw cow milk (including total solids-not-fat, protein, fat, lactose, density, freezing point, pH, total bacterial and fungal counts) were evaluated in Tabriz city. For this purpose, 60 samples of raw cow milk delivered to pasteurized milk factories, were randomly selected and evaluated during autumn 2015 to summer 2016. According to the results, the mean values of total bacterial and fungal counts were 7. 43± 1. 1 log CFU/mL and 3. 36± 0. 9 log CFU/mL, respectively. The mean of total solids-not-fat, protein, fat, lactose, density, freezing point and pH levels of the samples were %8. 56± 0. 2, %3. 15± 0. 12, %3. 38± 0. 32, %4. 65± 0. 3, 1. 0302± 0. 001 kg/L,-0. 533± 0. 006 ° H and 6. 75± 0. 07, respectively. The results of microbial count showed that hygienic quality of the raw cow milk in Tabriz city was not acceptable. The mean value of physicochemical factors except for the lactose, pH and total fungal count were not changed significantly in different seasons (P< 0. 05). The higher total microbial count in comparison with national standard levels indicates the poor sanitary condition of farms and inappropriate transport of milk to dairy plants. So, more attention to quality control of milk in the production chain is necessary.

The extracted dye from turmeric rhizomes has been used as natural colorant contains a various isomeric of chemical structures of curcuminoid. In addition, curcumin that is most pigment itself consists of three types I, II and III. These pigments were able to present the color spectrum of yellow to orange (tautomery) and yellow (variety curcumin). In this study, the effect of extraction conditions, the method of maceration as a solvent to solids ratio (1. 5-2), compared with ethanol to acetone (0-100) and extraction time (24-48 hours), color parameters (L * a * b *) of extract powder were analyzed using response surface method. Results indicate that polynomial models 2F (for a* parameter) and linear (for L* and b* parameters) models adequately explained the data variation and significantly represented the actual relationship between the independent variables and the responses.