ELECTRONIC JOURNAL OF FOOD PROCESSING AND PRESERVATION
Year:2017 | Volume:8 | Issue:2 |Papers Count:7

Background and objectives: Sour orange juice is used as a seasoning in preparation of different foods because of its sour taste. Although thermal processing is a common method to improve safety of sour orange juice, it induces the nutritional loss and undesirable compounds formation. Generally, chemical changes in food products influence the product color. By considering the relation between product color and its chemical changes, the objective of this work is to investigate the effect of thermal processing (temperature and time) on the color parameters including the browning index (BI) of sour orange juice.Materials and methods: In this study, the BI of product was measured using two different methods, the image processing method and the spectral analysis. The color changes were investigated using L*, a* and b* color parameters. In addition, the ascorbic acid content was measured using iodine titration method. Results: The results showed that the luminance (L*) of sour orange juice decreased as processing temperature and times increased, while a* (redness) and b* (yellowness) increased. An increase in the color intensity during thermal processing was shown by investigating the Chroma index. Total color changes (TCD), as an appropriate index in product color change, increased during processing. The reaction constant rate (k) of TCDincreased about 1.66 times as temperature increases, representing the color temperature affinity. The high activation energy (Ea) revealed the high temperature tolerance of components colo. Sour orange juice browning was found to be dependent upon the ascorbic acid content. A good correlation was also found between both of the applied methods to investigate the browning index.Conclusion: By considering the effect of thermal processing on the nutritional content of the sour orange juice, it could be reported that the color intensity of the product changed during thermal processing at different temperature and time; as the temperature increased, the rate of changes of different color parameters raised. Also it was observed that there was a high correlation between BI and ascorbic acid content in sour orange juice. By comparing the changes in BI and that of ascorbic acid content, it could be stated that the both methods (image processing and spectroscopy) were effective in analysis of BI. The image processing method is suggested in BI measurement due to its more simplicity, lower cost and not destructive effects.

Background and objective: The prediction of olive oil quality parameters is of great importance in modern approaches to quality control. One of the main problems in predicting olive oil quality during storage is the complexity of the physicochemical properties of raw material and the difference in data of planting, varieties, method of extraction, the type and amounts of the components of olive oil. Oxidative stability is one of the most important parameters in controlling virgin olive oil. Modeling the oxidative stability of olive oil with Adaptive neuro fuzzy inference system (ANFIS) can help to improve the quality control process for this product.Materials and methods: Parameters of the model design were acidity, peroxide value (PV) specific extinction coefficient K232, phenolic compounds as input variables and the extinction coefficient k270 as the output. In order to develop ANFIS model, number of membership functions, and different learning cycles by trial and error were used. Then, the network was trained for every different pattern models and the best model was selected based on statistical criteria. Results: This study has shown that some analyses such as acidity, peroxide value (PV) specific extinction coefficient K232, phenolic compounds are valuable in illustrating oxidative stability of olive oil, however no individual test can identify all problems associated with storage conditions or aging. Peroxide values and acidity were obtained between 7 to 15 mmol-equiv/kg and 0.16 to 0.84 mg KOH/g, respectively. The concentration of total phenols varied 77 from 381 to mg/kg. The lowest extinction coefficients k270 and k232 were found to be 0.1 and 1.73, while the highest values were 0.25 (k270) and 3.14 (k232). ANFIS technique was successfully used to modeling the rates of changes of physicochemical parameters associated to oxidative stability of olive oil. The best model with the least mean square error 0.012 and the best regression coefficient of 0.99 was obtained using trapezoidal membership functions, numbers memberships of 3 3 3 3 3 and learning cycle of 5. Conclusion: Analysis of the model revealed that the ANFIS is a powerful tool to predict the oxidative stability of olive oil. Therefore, by using the information from ANFIS model, olive oil producers will be able to predict olive oil quality.

Background and objectives: Wheat grain has an important value in the world nutrition. Evaluating the physical and microbial properties of agricultural products plays an important role during harvesting with machines, cleaning process and waste reduction. In this study, for the first time in Iran, the optimized effects of cleaning and moisture content at 40oC on the physical (useful besatz, unuseful besatz, hectoliter, thousand seed weight) and microbial (total count of bacteria and molds) properties of wheat grain (n-80 variety) in Golestan province, were modeled.Materials and methods: After determining the basic moisture content, samples with three levels of cleaning (0-100%), and different moisture contents (10-14% w.b) at 40oC were studied and modeled by response surface methodology using central composite design (face center) including 21 tests with five repeats at the central point.Results: The results showed that by reducing moisture content and increasing cleaning levels, useful and unuseful besatz decreased and hectoliter increased. Also increasing the cleaning percentage was more effective than moisture content reduction in reducing useful besatz and unuseful besatz. The lowest value of hectoliter was 72.58 (0.01kg. lit-1) at 40oC. The highest thousand seed weight at moisture content 14% (w.b) and cleaning level 100%, was 36.80 gr. Higher rate in increase in thousand seed weight was found in the higher moisture content than that in the higher level of cleaning. With increasing moisture content and reduction in cleaning level, total microbial count increased. Linear parameters of cleaning and moisture had a significant effect (p < 0.01) at 40oC on the total count of microorganisms in the linear model. Total microbial count increased by 52.7 and 90%, at moisture content 14% (w.b) and cleaning level of 10%, respectively in comparison to that in moisture content 10% (w.b). R2 for useful besatz, unuseful besatz, hectoliter, thousand seed weight, total counts of microorganisms and molds (colony/g) were 0.9463, 0.9818, 0.9677, 0.8255, 0.8547 and 0.9674, respectively. The results of optimization at 40oC showed that cleaning level of 100% and moisture content of 10% (w.b) resulted in storage of grain wheat with desirability of 94.1%.Conclusion: Regard to non-significant lack of fit and high values of R2 and adjusted R2, our selected models could accurately predict the experimental values for all studied properties.

Background and objectives: Stevia rebaudiana Bertoni, is an ancient perennial shrub of South America, with a great potential as a crop for the production of potent natural sweetener. it is suitable as a raw material for the production of functional foods due to its chemical composition and phytochemical compounds content. Stevioside has enormous sweetening power comparable to artificial sweeteners which are presented in various foods and beverages available in the market. This compound is about 300 times sweeter than sucrose. In this study, phenolic compounds were extracted from Stevia rebaudiana Bertoni leaves by maceration in methanol to evaluate antioxidant activity of its water-methanol extract and its antioxidant effect in dairy desserts.Materials and methods: Antioxidant activity of the extract was evaluated using reducing power test, DPPH radical scavenging activity and total antioxidant capacity and compared with synthetic antioxidant BHT. Antioxidant effects of Stevia rebaudiana Bertoni extract in dairy desserts was investigated using reducing power test and DPPH radical scavenging activity after 1, 3, 6, 9, 12 and 15 days storage. Results: Average total phenolic compounds in the Stevia rebaudiana Bertoni extract was 10.64 (Tannic acid equivalent) g/100g dry matter. Evaluation of antioxidant activity of the extract showed that DPPH free radical scavenging, reducing power and total antioxidant activity of the extract were directly correlated with the amount of phenolic compounds. Antioxidant activity was found to be concentration-dependent in all antioxidant assays. DPPH scavenging activity of methanolic extract of stevia was greater than BHT. Reducing power and total antioxidant capacity of BHT were significantly higher than those of ethanolic extracts. Dessert samples containing stevia showed higher DPPH free radical scavenging activity and reducing power compared with control sample. By conducting sensory analysis on desserts containing different percentages of Stevia rebaudiana Bertoni extract, samples with 0.75, 1 and 0.25% extract (due to high total acceptance) and also samples with 0% (as control sample) and 100% (complete sugar replacement) were selected. DPPH free radical scavenging and reducing power assays in dairy desserts showed that samples with higher amounts of Stevia rebaudiana Bertoni extract had higher activities. In addition, dairy desserts containing Stevia rebaudiana Bertoni extract showed high levels of free radical scavenging activities during two weeks storage that may result in delay in fat oxidation and extended shelf life of the product.Conclusion: The obtained results showed that antioxidant capacity of Stevia rebaudiana Bertoni extract is considerable; therefore it can be used as a good source of natural antioxidants.

Background and objectives: Compounds drived from Plants have been used for medicinal purposes for centuries because of their antimicrobial activity. The use of preservatives and anti-microbial materials is an approach for controlling pathogen bacteria in food stuff. Developing anti-microbial drugs is one of the most important advances in the treatment assumes. Due to their natural origin, herbal extracts are more compatible with body organism than antibiotics and their side effects are very scarce. Spinach as a source of new plant maybe used as an anti-oxidant and antimicrobial agent to deal with free radicals and microbial pollutions. The aim of this study was to evaluate the antibacterial effect of aqueous and alcoholic extracts of Spinach (varieties Mashhad) on pathogenic bacteria Staphylococcus aureus ATCC25923, Escherichia coli ATCC2592 and, Listeria innocua ATCC33090.Materials and methods: The susceptibility testing of bacteria was performed by disc diffusion method, and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extract were determined using broth micro dilution method. In disc diffusion method, Erythromycin, Gentamicin and chloramphenicol were used as a positive control for Listeria innocua, Staphylococcus aureus and Escherichia coli, respectively.Results: According to disc diffusion method, gram positive bacteria (Listeria innocua, Staphylococcus aureus) were the most resistant and Escherichia coli was the most sensitive bacteria. Also, MIC valuese of the aqueous extract of Spinach (varieties Mashhad) toward Listeria innocua, Staphylococcus aureus and Escherichia coli were determined as 46000 PPM, 48000 PPM and 28000 PPM, respectively, whereas MIC for the alcoholic extract was comparable (10393 PPM), on all tested bacteria. The both aqueous and alcoholic extracts of Spinach (varieties Mashhad) had antibacterial properties.Conclusion: Alcoholic extract of Spinach (varieties Mashhad) showed more potent antibacterial activity than aqueous extract on Escherichia coli. Also, the effect of its alcoholic extract on Escherichia coli was comparable with Erythromycin on Listeria innocua at disc diffusion test. Finally, it can be concluded that high amounts of flavonoids and terpenes, unsaturated fatty acids and inorganic materials are probably the most important inhibitory agents of spinach on gram-negative bacteria such as Escherichia coli. As a result, Spinach extract can be used as a natural antibiotic and preservative in food industries and pharmaceuticals.

Background and objectives: In this paper local pomegranate juice (50% v/v final solution) based gels made from gelatin or kappa-carrageenan with sucrose (2.6%, 5.8% w/v final solution) have been examined to determine their textural characteristics and viscoelastic properties. Pomegranate is one of the most important crops cultivated in Iran which extensively used as a source of variety of products. However, some especial properties of this fruit such as low pH, varied tastes, red color, and phenolic and anthocyanin compounds may affect final product properties. In this regard, it is required to study the influence of applying natural pomegranate juice on final gel quality. Since gelatin and kappa-carrageenan are two popular examples of protein and polysaccharide hydrocolloids which are available with low cost, in this work pomegranate gels were prepared based on these hydrocolloids. Generally, gel formulations include sugar as a taste and texture improver so its interaction with gel components and its effect on textural properties of pomegranate gel was investigated.Materials and methods: In order to determine textural properties like hardness, cohesiveness and springiness, texture profile analyses have been used. Also, to investigate viscoelastic properties, dynamic oscillation measurements were used and their rheological behavior was interpreted regard to loss tangent, elastic and viscos modulus.Results: The result of texture profile analysis show that incorporation of sucrose into gelatin based gels effectively increases hardness, cohesiveness and springiness. Furthermore, the results of oscillatory dynamic rheological measurements show that gelatin gels are more elastic and resist higher frequencies when sucrose concentration increased. Since gelatin has the protein nature, it has different electrostatic charges at different pH levels, so at lower/higher pH than pI it would be found with positive/negative charge. Accordingly, under acidic condition of pomegranate juice with pH lower than gelatin pI, gelatin may carry positive charge which able it interact with anionic agents in the media. In this case, presence of phenolic compounds, flavonoids and tannins with anionic nature in pomegranate juice can enhance these interactions. The results of our investigations have shown that applying pomegranate juice and sucrose for the preparation of gelatin gels leads to form a high quality gel due to proper pH of the juice and adequate hydrogen and electrostatic interactions. In case of Ƙ-carrageenan gels, increase in the sucrose level enhances viscose modulus and decrease hardness and cohesiveness because of preventing the formation of a solid-like viscoelastic texture. Although low concentration of sucrose can improve gel textural properties, at high concentration it inversely affects on carrageenan gel elasticity. The major reason for this effect may be due to sucrose prohibition from cross-linking interactions. Moreover, different compounds in pomegranate juice may have synergistic effect on decreasing textural quality of carrageenan gels by sucrose. Conclusion: The results of this study indicate that high quality pomegranate gels based on gelatin and Ƙ-carrageenan with optimum concentration of sucrose can be produced with no adverse effects of natural conditions of pomegranate juice (low pH and contained ions) on the quality.

Background and objectives: Fat reduction in cheese causes inappropriate changes in sensory properties and functional parameters. In order to imitate the various functions of fat in a low fat product, attention should be given to issues such as product consistency, modified dry matter, the effect of particle size on mouth feel, color, flavor and rheological properties. In this respect, methods such as use of fat replacers and technical support like homogenization can improve these properties. The aim of this study was to evaluate the effect of homogenization on the properties of Mozzarella cheese.Materials and methods: low fat Mozzarella (less than 6% fat) was produced by fat replacement with three whey protein concentrates (with 35, 53 and 90 percent of purity). In order to evaluation of homogenization effect, the cream was homogenized at 120-130 bars and added to skim milk with fat replacer. Differences were measured by comparison of treatments to control group involved 2 treatments; low-fat Mozzarella without fat replacer that produced by homogenization and full-fat Mozzarella, while process technology effects on composition and sensory properties of Mozzarella were studied. Data were analyzed using one-way analysis of variance (ANOVA) at 95% confidence interval and paired sample t-test using SPSS.Results: Moisture (54-61.59) and fat (6-6.5) content of low fat Mozzarella samples produced by fat replacer were significantly higher than those of full fat cheeses. It was cleared that homogenization increased moisture content which was significant in two treatments (B&G), (p<0.05). Data indicated that 12% TCA-soluble nitrogen was lowest in full fat cheese but any differences were not significant. Sensory analysis was cleared that the highest score of lightening was belonged to I and the lowest was belonged to E treatment (p<0.05). It was indicated that homogenized treatments get better score for color than unhomogenized while all the differences were significant (p<0.001). However the highest score of desirable flavor was indicated for B treatment. About chewiness data cleared that the highest score was for B treatment and the lowest score was for I treatment. The chewiness of homogenized treatment was lower than unhomogenized. In customer acceptance by 30-untrained assessors it was indicated that the highest number of reported "pleasant taste" was related to treatment B and there were no unpleasant taste. Conclusion: Addition of fat replacer caused increasing the moisture content and homogenization cause low increasing in fat, lightening the color, improving flavor and chewiness of low fat Mozzarella. These results are briefly showed that although whey proteins are crucial in improving the taste but the effect of homogenization is more important.