مجله علوم غذایی و تغذیه
سال دوازدهم شماره 4 (پاییز 1394)

Hydrocolloids (gums) are components of food ingredients that are affected by thermal treatments during transportation، processing، storage and distribution of food. In this study، the effect of heat treatment on the color changes، rheological and textural (firmness، adhesiveness and consistency) properties of Basil seed gum are investigated. Basil seed gum is extracted in order to evaluate the rheological، textural properties and color. Solutions with different concentrations were prepared and were subjected to different thermal treatments (25، 50، 75، 100، 121°C، for 20 min). Applied thermal treatments increased the viscosity of Basil seed gum. Texture of the prepared gels had a good resistence against heat treatments and hardness، adhesiveness and consistency values of Basil seed gum gel (3%) at 121°C were 51. 3gr، 23. 75 gr/s، 211. 99 gr/s. By increasing the temperature of the treatment، the color of the samples became brighter (increase in L). The results indicated that Basil seed gum has pseudoplastic behavior and Power law model is suitable to evaluate it.

In the formulation of meat products such as sausages, some non meat proteins and non protein hydrocolloids are usually employed to improve the rheological properties, nutritional value and reduce the fat content, therefore gelatin might be considered as an option among others. In this study, bone- gelatin gel has been used in beef sausage in order to reduce the amount of meat and also evaluate its effect on the physicochemical and sensory properties of the final product. Physicochemical analysis (moisture, ash, protein, fat, pH, bloom and viscosity) have been accomplished on bovine bone gelatin. A 20% gel of gelatin was prepared and used at the concentrations of 0, 3, 5 and 10% as meat substitute in the sausage formulation. Samples were produced in two batches and analyzed for chemical, physical and sensory characteristics. Moisture and fat contents of all of the samples were lower than the control, therefore in sausage with 10% gelatin, the highest reductions (3.69 and 3.87%, respectively) were observed. The results of texture profile analysis showed that by increasing gelatin concentration in the formulation, the hardness was decreased but cohesiveness was increased. Meanwhile the addition of gelatin leads to an increase in the parameter b* as compared to the control. All of the gelatin- containing samples obtained higher scores from overall acceptability aspect in the sensory tests. According to the results regarding physicochemical and sensory tests, the sample containing 5% gelatin gel might be selected as the most suitable formulation.

Olive oil is one of the most consuming oil and plays important roles in human health and nutrition. Due to the fact that most olive oils consumed in Iran are imported, therefore the control and olive oil regulations have important roles in food safety and consumption. This study evaluates the chemical characteristics of imported extra virgin olive oils. In this research work eight samples of extra virgin olive oils were examined for fatty acid composition, acidity, peroxide value, anisidine value, totox value and oxidative stability (Rancimat) according to the Iranian National Standards. The results of fatty acid composition as expected for olive oils indicated that oleic acid was the predominant monounsaturated fatty acid with smaller quantities of saturated fatty acids namely palmitic and stearic acids and polyunsaturated fatty acid such as linoleic acid. Other examined factors such as acid, peroxide, anisidine, totax values and oxidative stability were different among the oils that might indicate different qualitative factors involved among the oils. Interpretation of the data suggests that the measured factors are in the standard range, however some other features namely climate and agricultural conditions might affect the quality of the product.

The consumption of probiotic products due to their functional effect on the consumers has been increasing in recent years. One of the effects is the production of B group vitamins, specially folic acid and its derivatives by probiotic bacteria. The aim of this study is to examine the growth rate of folic acid in indigenous set and probiotic yogurt. In order to prepare yogurt, milk samples from cow, sheep and goat were provided and microorganisms consisting of Lactobacillus casei (y2b4, JQ41273501) and ordinary yogurt culture (YC-X11) were employed. The samples were incubated for four hoursat 42oC. Folic acid produced during fermentation and storage for 14 days at 4oC were determined using liquid chromatography (HPLC). Furthermore, acidity and pH changes and sensory scores were determined on the first, 7th and 14th days. The ability of folic acid production by indigenous probiotic in all the milk samples (cow, sheep and goat) were observed. The rate of folic acid produced by probiotic bacteria was more than that of set yogurt (P <0.05). pH changes during storage period has a downward trend while the acidity took an upward trend on the 14th day of storage time (P <0.05). In general this study has indicated that indigenous Lactobacillus casei is able to increase the folic acid rate of production up to three times as compared to that produced by the set yogurt. The inoculation of probiotic had no significant effect on the sensory properties of yogurt and an acceptable product has been produced.

Apricot is a soft fruit with a short storage life. A considerable quantities of this fruit are wasted due to its poor resistance to impact, unsuitable transport and storage conditions. Appropriate packaging is a good policy to decrease the wastage of this product in the post harvest and marketing stages. In this research, the effect of chitosan-based nano-emulsion and chitosan-based nano-containers on the microbial properties of two Iranian apricot cultivars namely the 58-Shahroud (526) and the ChinKalaghi (510) were studied. All the apricot fruits were divided into three groups; without any treatments as the control, coated with the aforementioned wax and were packed in the chitosan nano-based containers. The treated fruits were then stored at 0°C at relative humidity of %90± 5 for 8 weeks. During the cold storage period, required microbial tests were performed every week. SEM test was also carried out. The results showed that there are significant differences between the factors of coating, cultivar and storage time in terms of microbial tests. Chitosan nano-emulsion and chitosan nano-container have important roles in the prevention of the microbial growth as compared to the control. SEM confirmed a nano-based coating on the skin of both cultivars. The application of chitosan as a coating film or chitosan based nano containers might be regarded as a suitable method to reduce antimicrobial contamination of apricots.

Lycopene is a useful natural pigment however it is quite unstable due to the presence of conjugated double bonds in its structure. A useful method to protect lycopene against environmental conditions such as oxygen is microencapsulation. The first step is to have proper microcapsules by preparing a stable emulsions of lycopene. Therefore the object of this study is to develop a RSM-based optimization technique to improve the stability of lycopene emulsion by natural biopolymers and to obtain the optimum operating conditions. According to the Response Surface Methodology (RSM) design, eighteen emulsions were prepared. Lycopene was dissolved in soybean oil to prepare a solution of 5%w/w lycopene in oil. maltodextrin was dissolved in water and kept overnight. Gelatin was dissolved in hot water and added to rehydrated maltodextrin at the ratio of 1:19. Then lycopene was mixed gradually in gelatin and maltodextrin solution by using rotor stator homogenizer the stability of the emulsion was investigated by monitoring droplet size, viscosity and creaming index. Homogenization speed, lycopene content and gelatin and maltodextrin concentration had significant effects on droplet size, creaming index and viscosity of the emulsions. The quadratic model was sufficient to describe and predict the responses of droplet size but for the viscosity and creaming index, the linear models were proper and suitable. The graphical optimization method was adapted to find the best emulsifying conditions and it was predicted that the homogenization speed of 18000 rpm, lycopene content of 18.07w/w and gelatin and maltodextrin concentration of 35.28% w/w would be the optimum conditions for preparing lycopene emulsion.

Intoduction: During heat treatment of foods, reactions occur between reducing sugars and amino groups of food components, known as the Maillard reactions. Five hydroxymethy furfural (HMF) is an intermidiate compoud formed as the result of this reaction. The aim of the present study was to examine HMF content of dried fruits and evaluate its relationship with the chemical characterisatics. Total of 50 samples from various types of dried fruits were collected and subjected to quantitative HMF determinations employing HPLC apparatus. The chemical properties of the selected fruits were measured using conventional standard methods. Pearson analysis was performed to test any correlations between HMF content and the chemical properties. The highest and the lowest amount of HMF contents were determined in fruit bread(8569.85 mg/kg) and golden raisin (80.49 mg/kg), respectively. Correlation analysis between the chemical properties and HMF content showed a negative relation inrespect of HMF and moisture content of both currant and dark raisins (r= -0.86, p<0/05) and a positive correlation between the acidity and HMF content of fruit breads (r=0.81, p<0.05) and also between total sugar and HMF contents in date (r=0.81, p<0.05). HMF content of the dried fruits was high with mean of 2243/19 mg/kg. This might lead to high dietary exposure to this compound. Further studies are required to clarify the extent of HMF bioavailability. It is also concluded that the chemical properties affected by preservation and processing conditions are strongly related to the HMF content in different fruits.

Sesame seed and flaxseed are rich sources of the essential fatty acids and due to their unique nutritional characteristics valuable research works have been carried out on these oil seeds. In this study, some of the chemical characteristic of sesame and flaxseed are evaluated and compared to each other. Sesame and flaxseed were purchased randomly from Grand Bazaar of Tehran. The fat, fiber, protein and ash contents were determined by standard methods of evaluation. The cold press hexane extracted oil was subjected to series of tests consisting of fatty acid composition, Peroxide, acids, totax and anisidine values. The induction period, the oil resistance to oxidation was also measured. This study indicated that the amounts of protein, fiber, ash and acid value in the flaxseed were significantly higher (P<0.01) while the amount of oil content, totox and anisidine values and resistant to oxidation were significantly lower in the flaxseed as compared to the sesame seed. In respect of peroxide index, there was no difference between the examined samples. The fatty acid analysis showed that linoleic acid (W6) and linolenic acid (W-3), were the predominant fatty acids in sesame seed and flaxseed oils respectively. The results of this study indicated that sesame seed and flaxseed are rich sources of essential fatty acids, proteins, fiber, minerals and other nutrients. Thus, the extracted oils might be considered valuable oil resources and might be employed in food formulations.

Tomato is an important economical vegetable crop in Iran. Approximately 30% of the crop is lost during the harvest to consumption chain. The high generation of ethylene production in tomato is the main reason. In this study we investigate and evaluate the effect of different concentrations of MCP on the physicochemical properties of this popular vegetable product. The Respona cultivator was selected from a farm in the city of Asadabad. Tomatoes were collected at the point of colour change. Tomatoes were treated with 1-MCP at different concentrations (0.35, 0.70, 1.00 and 1.35) for the period of 12 and 24 hours and during storage for 4 weeks at 12± 2 with relative humidity of 85-90% were examined for total soluble solid, total acidity, colour and ethylene concentration. This examination was carried out in a completely randomized design in triplicate order. The statistical analyses were carried out using SPSS software. The results indicated that 1-MCP had significant effect (p<0.05) on the total soluble solid percent, acidity, colour and ethylene concentration. 1-MCP solution at concentrations of 1.0 and 1.351l/l had the highest effect in the prevention of increased Brix of tomatoes. Ethylene concentration was decreased for all the samples as compared to the control and reductions were proportional to the increased concentrations of 1-MCP. 1-MCP also caused decreases in the acidity and colour. The results showed the significant effect of MCP (p<0.05) on the soluble solids, acidity, color and accumulation of ethylene concentration.

Sesame oil because of having lignans such as sesamin and sesamolin has greater resistance against oxidative degradation as compared to other edible oils. Roasting process can make a tremendous positive impact on the oxidative resistance of the oil. The aim of this work was to evaluate the roasting conditions of sesame in terms of temperature and time using response surface methodology regarding the highest rate of oxidative resistance and best color of roasted sesame oil. In order to evaluate the roasting conditions, the two factors of temperature (200, 215 and 230 °C) and time (15, 25 and 35 min) were used in 3 levels. The total number of tests for each sample was 12 and oxidative resistance and color (XE and L index) were considered as responses. After data analysis by the software, statistical analysis of the models related to the stability and color (XE and L index) were evaluated. The results indicated that the temperature was more effective than the time in oil oxidative resistance changes and by increasing the temperature and time, the oxidative resistance and XE index increased while L index decreased. The optimal condition of roasting for brown sesame seeds was at the temperature of 216.86°C and time of 19.32 minutes while for the white type, the temperature of 220.47°C and the time of 15 minutes were considered as the optimum condition.