ELECTRONIC JOURNAL OF FOOD PROCESSING AND PRESERVATION
Year:2019 | Volume:11 | Issue:1|Papers Count:9

Background and objectives: In high voltage electrostatic field technique, by applying a high voltage electric field (HVEF) in a needle-plate electrode system, air at the surface of food product is ionized, and a volumetric flow known as corona wind is formed, that increases the heat transfer coefficient in food product by volumetric heat generation. In this thechnology, ozone generation followed by the corona discharge and air ionization, are capable to reducing microbial contamination; on the other hand, since ozone is a strong oxidizer, there is a risk of lipid oxidation. The aim of this paper is using high voltage electrostatic field for thawing of chicken breast, and investigating its effects on microbial count and lipid oxidation. Materials and methods: First, fresh chicken breast were cut into equal cubes (2×2×2 cm3) by a designed cast and sharp razor, then, were frozen by a freezing tunnel with forced air circulation at-30 0C and 1 m/s air velocity, after vacuum packaging in polyethylene bags. The frozen samples were kept at-180C until use. Thawing under HVEF at three different voltages (from the corona start voltage to the breakdown voltage), and specific electrode gaps were done. The control sample was subjected to no HVEF but thawed conventionally by still air method. Fat oxidation of thawed samples were investigated at first, third, fifth, and seventh days intervals during storage at refrigerator. The thawed samples were kept at refrigerator (4± 10C) after packaging, and evaluated for microbiological tests (total microbial count and psychrotrophic), and the oxidation kinetics were investigated. Total microbial count during first, third and sixth days of storage at refrigerator, by pour plate at 300C for 72 hours, and psychrotrophic bacteria count during ten days storage at 6. 50C by surface plate were investigated. Results: The equation resulted from TBARS-time changes curve, is linear. By evaluation of zero-order kinetic model, the kinetic rate constant was determined at different treatments. The kinetic rate constant had no significant difference with control at low electric field strength (1. 5 kV/cm); while, this factor was more intense with increasing electric field strength (2. 25 and 3 kV/cm). Generally, malonaldahyde formation rate of thawed chicken was increased by increasing voltage and decreasing electrode gap during storage. However, at corona start voltages, malonaldahyde formation rate constant was less than control. Results from microbial growth showed total microbial count decreased at HVEF thawed samples compared with control and fresh chicken during six days storage. Total microbial count in the case of control was 1. 07×105 cfu/g at first day, that was increased to 7. 82 ×106 cfu/g at sixth day, and in the case of HVEF thawed samples at 8 and 10 kV, were 5× 104 cfu/g and 3. 36×104 cfu/g at first day, that were increased to 1. 36×106 cfu/g and 1×106 cfu/g at sixth day, respectively. However, total microbial count of fresh chicken was increased from 9. 73×104 cfu/g at first day to 6×106 cfu/g at sixth day. On the other hand, storage at 6. 5 0C during 10 days, decreased the psychrotrophic microorganisms significantly at HVEF thawed samples (P<0. 05). Conclusion: Due to the importance of thawing for products susceptible to spoilage, such as chicken, it is possible to benefit from HVEF thawing method to decreasing spoilage and increasing shelf life, by applying 2. 25 kV/cm electric field strength.

Background and objectives: Date seed is one of the major waste of date processing plants and a rich source of dietary fiber and contains high levels of phenolic compounds so potentially can improve the growth and survival of probiotic bacteria. In this research, the effect of adding date seed powder (DSP) on some quality properties and viability of probiotic bacteria in set yogurt was investigated. Materials and methods: The DSP was added at three levels of 0. 5, 1 and 2 percent to set yoghurt containing Lactobacillus acidophilus LA-5 and Bifidobacterium lactis Bb-12. During the 21 days of storage in the refrigerator, physicochemical (pH, acidity, dry matter, syneresis) and sensory properties and viability of probiotic bacteria were evaluated on days of 1, 7, 14, and 21. Results: The results showed that with increasing the amount of DSP, the pH of all samples decreased during the first day and storage period while the acidity and dry matter percentage were increased. Increasing the amount of DSP resulted in a reduction in the percentage of syneresis from 29% to 24% in first day, although during the storage, it increased and reached 33%. By increasing the concentration of DSP, probiotic counts in all samples from 8. 2 (log cfu ml-1) was improved to about 9. 5, although it decreased during storage and decreased to at least 7. 4, but never exceeded the recommended limits For probiotic products (107cfu g-1). The sensory evaluation showed higher score in color, flavor and overall acceptance of yogurt when DPP was added to samples but it declined during storage period. Conclusion: In general, one percent DSP was led to improve survival of probiotic bacteria and quality characteristics of yogurt, for up to two weeks after production.

Background and objectives: Different intrinsic and extrinsic factors may initiate the oxidation of lipids. The initial products of oxidation are tasteless and odorless and after degradation and production of secondary products, the off-flavors and off-odors will appeare in edible oils. This is a great concern in food industry, because it decreases the shelflife of food products. Free radicals are produced during chain reactions in lipid oxidation process. To avoid this, synthetic antioxidants are usually used which are sensible to heat and are hazardous to human health and may cause cancer. Polyphenols have antioxidant activity and absorb free radicals. Thus, the vegetable oils rich in polyphenols can affect human health. In this research, we aimed to investigate the application of natural extract of olive leaves as a natural antioxidant to avoid soy oil oxidation and to compare it with synthetic antioxidants. Matherials and Methods: In this project, methanol and acetone solvents in an ultrasonic apparatus were used to extract the phenolic compounds of the leaves of Mary and Yellow varieties of olive. The amount of phenolics, as well as their antioxidant effect on the oxidation of crude soybean oil, was investigated. The phenolic contents were measured by Folin– Ciocalteu method and the antioxidant activities of the extracts were determined by two controlling methods of DPPH radical-scavenging activity and Ferric reducing power, and then the results were compared with antioxidant activities of synthetic antioxidants. The antioxidant effects of different concentrations of the extracts on delaying the oxidation of crude oil were studied by determining their peroxide and thiobarbitoric acid values. Results: The leaves of Mary variety showed the highest amount of phenolics (101. 382mg/g), as determined by measureing the phenolic contents. The results suggested that the methanolic extract of Mary variety had a better antioxidant activity than the other natural antioxidants, compared to synthetic antioxidants BHT and TBHQ. In addition, it was shown that the radical scavenging activity was directly correlated with the increase of the extract concentration. Then the methanolic extract of Mary variety at three levels 100, 200 and 500 ppm and BHT and TBHQ antioxidants at 100 and 200 ppm were added to antioxidant-free soy oil. The control oil, which lacked antioxidants, showed the highest peroxide and thiobarbitoric acid values. Conclusion: The methanolic extract of the Mary variety showed the highest extraction efficiency as well as the most antioxidant activety. In addition, it was shown that the radical scavenging activity was increased by the increase of extract concentration. The methanolic extract of Mary variety at the concentration of 500 ppm was comparable with the synthetic antioxidants at the levels of 100 and 200ppm.

Background and objectives: The use of hydrocolloids in food industries has dramatically increased in recent years. Although concentrations of less than 1% are usually used in food systems, they can have important effects on texture, taste, shelf-life, and organoleptic properties of foods. The importance and use of hydrocolloids depend on their functional properties, which are affected by molecular structure and concentration of hydrocolloids as well as their reaction with other food compounds (salt, sugar, fat, and protein), pH, and processing conditions (e. g., temperature). Studying factors affecting the extraction of hydrocolloids is particularly important for finding optimal extraction conditions. We studied the effect of treatments of aquatic extraction process on chemical and rheological properties of fenugreek seed gum. Materials and methods: In this study, the effects of 3% and 5% sodium and potassium chloride salts and pH of 3 and 6 on chemical compositions of extracted gum were studied. Protein content, fat, ash and moisture were determined according to AOAC Standard methods (2005). Total sugar was determined by phenol-sulfuric acid method by using D-glucose as standard at 490 nm. Rheological properties of fnugreek seed gum were carried out using a rotational viscometer Brookfield for gum concentrations (0. 5-1%) at 25 ° C. The flow behavior index (n) and consistency index (k) values were computed by fitting the power law model. means were compared using the LSD test (p<0. 05) in SPSS v. 16. Results: Extraction variables had significant effects on rheological parameters, chemical composition and extraction efficiency of green seed resin. A substantial part of fnugreek seed gums were composed of polysaccharide (84. 22± 0. 63% maximum) in the sample treated with KCl 3%, and pH 3. The efficiency of gum extraction was significantly influenced by the type and concentration of salt. However, pH had no significant effect. The apparent viscosity decreased with increasing shear rate in all samples, which indicated strong shear thinning behavior with np<0. 41. Conclusion: The highest gum extraction yield of fenugreek seed was 17. 5± 1. 63%, which was obtained with pH 3 and potassium chloride 3%. The power law model adequately describes the non-Newtonian behavior of green seed resin at various values of pH in the presence of salts with regression coefficient in excess of 95%. Fitness of data in the model showed that consistency coefficient (Kp) and flow behavior index (􀝊 􀯣 ) decrease with increasing concentration of salt, while consistency coefficient and flow behavior index behaved opposite each other with increasing pH from 3 to 6 and resin concentration from 0. 5% to 1%. Potassium chloride had the highest effect on viscosity of resin solution and sodium chloride had the lowest effect, with the same concentrations.

Background and objectives: Fortified foods provide not only nutritional requirements, but also have positive effects on host. Puffy snack consists of whole grain bulgur and flour puffed by using extruder. Pumpkin is a good source of carotene, water-soluble vitamins and amino acids. Pumpkin can be processed into flour which has a longer shelf life. Because of its highlydesirable flavour, sweetness and deep yellow orange – red color pumpkin flour has gained much attention. Materials and methods: For the production of pumpkin powder, after the skin and seeds was removed, the edible part was cut into pieces of 5 mm and dried in the dryer with hot air (65° C) at 1 m/s flow rate for 8 hours to a moisture content of 10%. In this study, the effect of replacing corn flour with pumpkin powder (at four levels of 0, 10, 15 and 20%) on physicochemical and sensory properties of snack was evaluated. The mean values were compared with Duncan test at 95%. The physicochemical properties of puffy snack evaluated were moisture content, total polyphenolic compounds, fiber, β-carotene, density and texture. Results: In terms of crispiness, there was no significant difference between prepared snacks (P>0. 05), but moisture contents were found to be significantly different in the range of 2. 58 – 5. 11 % in different samples. The highest amount of β-carotene (0. 45 mg/100 gr) was observed in the puffy snacks containing 20% pumpkin powder and the lowest amount was found in control (0. 09 mg/100 gr). Increasing the pumpkin resulted in significant increase in total phenols (in the range of 433-2203 mg/L). The higher levels of substitution led to manufacture products with the higher expansion rate than the control sample. The highest rate of expansion rate was for puffy snacks with 20% pumpkin powder which was significantly different with other treatments (P<0. 05). The results of sensory evaluation showed that the puffy snack containing 20% pumpkin powder had the highest score for color, texture, flavor and total acceptance. Conclusion: Significant differences were found for the amounts of fiber and β-carotene, expansion rate, density and texture when the new produced samples were compared to the control (P<0. 05). According to the physicochemical and sensory results, the puffy snack containing 20% pumpkin powder can be introduced as the best formulation.

Background and objectives: Nowadays, due to the increasing use of plastics in food packaging and the problems arising from the lack of environmental degradation of them, using starch-based natural polymer in food packaging has increased. Edible films and coatings act as barriers against moisture, oxygen transfer, aroma and oil, and increase the quality and shelf-life of the products. These films can be incorporated with active agents such as anti-oxidants. In this research, in order to fix the flaws and to improve the physical and mechanical properties of starch film, different concentrations of carboxymethyl cellulose (CMC) and Chavill essential oil were incorporated into the films. The composite prepared films were used for butter packaging to reduce oxidation and to increase the shelf-life. The effect of these factors on chemical properties of final product was evaluated. Materials and methods: In this research, starch films containing CMC (5, 10 and 15%) and Chavill essential oils (0. 5, 1, 1. 5 %) were produced by casting method. Chavill essential oil was prepared with water distillation. Physical tests including tensile strength, water vapor permeability, moisture absorption, solubility were done. After packing of butter, the chemical tests including the peroxide value and acid value were assessed in different time intervals. Results: The results showed that tensile strenght of starch films containing CMC and Chavill essential oils was increased with increasing CMC concentartion; while it was decreased with increasing the Chavill essential oils. With increasing the amounts of CMC and Chavill essential oil, water vapor permeability was reduced. Increasing CMC and Chavill essential oils cauesd a decrease in water absorption and solubility of the prepared films. In addition, the effects of these two factors on chemical properties of butter showed that they could reduce the rate of peroxide and acid values elevation. Conclusions: Regarding the different effects of CMC and Chavill essential oils, it can be concluded that by increasing the amount of these two variables, physical and mechanical properties of films were improved and a reduction in acid and peroxide values of butter was observed. Finally, considering the improvement of physical and mechanical properties of prepared films and reduction of peroxide and acid values of butter, starch-CMC containing Chavill essential oils is recommended as replacer for aluminum foil.

Background and objectives: Turbidity is a desirable property in some juices such as carrotkiwi juice that is influenced by the presence of released pectin. Pectin methylesterase (PME) causes turbidity loss in the juice because of desterification of the pectin. Thermal processing is the most common method to PME inactivation. The aim of this study was investigation of PME inactivation during thermal processing of carrot-kiwi juice at different temperature. Materials and methods: To study the PME inactivation, the carrot-kiwi juice was heated at 60, 70, 80 and 90 ℃ at different time (proportional to the temperature). D and Z-value and thermal dependence kinetic parameters consisting of activation energy (Ea), enthalpy (Δ H), entropy (Δ S) and free energy (Δ G) of the thermal inactivation of PME were calculated. Results: Based on the obtained results, the Z-values of heat sensitive and heat resistant isoforms of PME in the juice during processing at 60, 70, 80 and 90 ° C were calculeted 17. 85 ° C and 22. 27 ° C, respectively. The required Ea to inactivate the heat sensitive and heat resistant isoforms of PME in the carrot-kiwi juice were 356. 83 kJ/mol and 257. 17 kJ/mol, respectively. Also, enthalpy for inactivation of the heat sensitive and heat resistant isoforms ranged between 354. 1 to 353. 8 kJ. mol-1 and 254. 4 to 254. 1 kJ. mol-1, respectively. During the juice thermal processing, the entropy of the inactivation of the heat sensitive and heat resistant isoforms were calculated 0. 79 to 0. 73 K-1. kJ. mol-1 and 0. 47 to 0. 43 K-1. kJ. mol-1, respectively. The free energy related to the inactivation of the heat sensitive (91. 1 to 87. 3 kJ. mol-1) and heat resistant (97. 9 to 97. 0 kJ. mol-1) isoforms of PME were measured. These results represent the effect of temperature on the protein structure of the PME. In addition, the effectiveness percentage of the come up time (CUT) on inactivation of the heat sensitive and heat resistant isoforms of PME in the carrot-kiwi juice were computed. Conclusion: By considering the effect of come up time and thermal resistance of the heat sensitive isoform of PME, the required pasteurization time for carrot-kiwi juice at 75, 80, 85, 90 and 95 ℃ were 22. 14, 11. 61, 6. 09, 3. 19 and 2. 01 min, respectively.

Background and objectives: Due to safety concerns and health aspects over the use of synthetic antioxidants, the natural antioxidant compounds are considered by researchers. In the recent years a great deal of attention for application of natural antioxidants, has led to studies in investigation of antioxidative or bioactive potential of hydrolysates peptides from plant or animal sources. Bioactive peptides are considered specific protein fragments that are inactive within the sequence of the parent protein, after they are released by enzymatic hydrolysis, they may exert various physiological functions such as antioxidative activity. Antioxidant activity of bioactive peptides can be attributed to their radical scavenging, metal ion chelation and inhibition of lipid peroxidation properties of peptides. Materials and methods: In the present study, response surface methodology was used to optimize hydrolysis conditions for preparing protein hydrolysate from the whey protein, using Alcalase. The investigated factors were temperature (43-55° C), time (60-173 min) and enzyme/substrate ratio (40-90 AU/Kg protein) to achieve maximum antioxidant activity. Experiments were designed according to the central composite design. Results: The optimal conditions to achieve the highest superoxide free radical scavenging capacity were as: temperature (47/2 ° C), time (104/02 min) and enzyme/ substrate ratio (96/85 AU/Kg protein). Under these conditions superoxide free radical scavenging capacity was 63/44 %. Regression coefficient for the model (Quadratic type) was 0. 989, indicating the high accuracy of the model to predict the reaction conditions considering different variables. Conclusion: Advances in the technology of preparing protein hydrolysate has provided the opportunity of use of unavailable protein sources. The optimization of antioxidant activity of protein hydrolysate, can save time, cost and amount of enzyme needed for hydrolysis. The Results indicated that whey protein hydrolysate has the potential to be applied as a natural antioxidant in food and pharmaceutical ingredients in the future.

Background and objectives: Grapefruit, like other vegetables and citrus fruits, grows during certain seasons of the years. Grapefruit juice has a therapeutic effect. Water content of grapefruit is about 80 to 90%. The concentration of the grapefruit juice is the most economic processing method. In the current study, the effect of concentration on the physicochemical properties and rheological characteristics of concentrated grapefruit juice at several Brix levels were investigated. Materials and methods: Grapefruit (Duncan varieties) was purchased from local markets. After juice extraction, the grapefruit juice was concentrated using vacuum rotary evaporator (60 ° C and 60 rpm) in several ° Brix (9. 5, 22, 34. 5, 47, and 59. 5). Soluble solids (° Brix), pH, density, opacity, color parameters and rheological properties of the samples were measured. Results: pH value of the fresh juice was 2. 77± 0. 07 (Brix 9. 5), which reduced to 2. 26± 0. 05 (° Brix 59. 5) after concentration (p<0. 05). Density and turbidity of the samples increased with the increasing of soluble solid materials via concentration (p<0. 05). The turbidity of ° Brix 59. 5 concentrate decreased compared to the ° Brix 47 concentrate due to the formation of the higher molecular weight compounds after a long heating time. By concentration, lightness (L*) of samples decreased, but both of redness (a*) and yellowness index (b*) were increased significantly (p<0. 05). Based on rheological properties, all samples showed gel-like behavior (G’ >G’ ’ ) in the frequency range of 0. 1-10 Hz. Even at low Brix (9. 5) similar behavior observed. The complex modulus (G*) of all samples increased with an increase in solid soluble material contents. In fact, at first rheological behaviors of samples were gel-like and after concentration was liquid behavior. This change may be related to the pectin degradation after thermal treatment of grapefruit juice. Conclusion: According to the above results, the concentration had a significant effect on physicochemical parameters and rheological properties of grapefruit juice. These rheological properties could be associated with the particle size distribution of the grapefruit concentrates. In subsequent studies, the study of the relationship between particle size distribution and rheological properties of grapefruit concentrate is recommended.