Food Technology
Marjan Karami; Leila Nateghi; Simin Asadollahi
Abstract
Introduction Oxidation of lipids results in changes that may affect the nutritional quality, wholesomeness, colour, flavour and texture of food. The aim of this study was to investigate the type and amount of phenolic compounds in ethanolic extract of aloe vera gel as a source of natural antioxidant ...
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Introduction Oxidation of lipids results in changes that may affect the nutritional quality, wholesomeness, colour, flavour and texture of food. The aim of this study was to investigate the type and amount of phenolic compounds in ethanolic extract of aloe vera gel as a source of natural antioxidant and its effect on the oxidative stability of soybean oil.Using synthetic antioxidant due to the possibility of toxic and carcinogenic effects is limited. Thus, it is important to find an alternative to synthetic antioxidants by natural antioxidant. 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 appeared in edible oils. This is a great concern in food industry, because it decreases the shelf life 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 aloe vera gel as a natural antioxidant to avoid soy oil oxidation and to compare it with synthetic antioxidants.The rate of oxidation reaction can be delayed by adding antioxidants. Consumers today tend to use natural antioxidants instead of synthetics. The overall purpose of this study was to investigate the effect of adding ethanolic extract of aloe vera gel as natural antioxidant on improving the stability of soybean oil. Materials and Methods The compounds in ethanolic extract of aloe vera gel were determined using GC / MS. The antioxidant activity was evaluated by the method of DPPH. For this purpose, ethanolic extracts of aloe vera gel were added to soybean oil in four different concentrations (500, 1000, 1500, 2000 ppm) and peroxide value, acidity, thiobarbituric acid, total phenol, oxidative stability to Rancimat method, fatty acid profile and sensory evaluation were performed on soybean oil samples and compared with the control sample containing 120 ppm BHA and soybean oil sample without adding antioxidants during 30, 60 and 90 days of storage at 25 ° C. Results and Discussion The results showed that by increasing the concentration of aloe vera extracts from 500 to 2000 ppm, the oxidation rate decreases during 90 days of storage, the amount of peroxide, thiobarbituric acid and acidity of soybean oil containing 2000 ppm ethanolic extract of aloe vera gel was lower than the control sample containing 120 ppm BHA. The total phenol content and free radical scavenging and stability to oxidative degradation by Rancimat method in soybean oil sample containing 2000 ppm aloe vera ethanol extract was higher than soybean oil samples containing BHA120 ppm. Evaluation of sensory properties showed that no significant difference was observed between the sensory properties of the oil sample containing 2000 ppm ethanolic extract of aloe vera gel and the control soybean oil sample of BHA120 ppm. Conclusion Considering that the sample of soybean oil containing 2000 ppm ethanolic extract of aloe vera gel had higher phenol content and free radical scavenging and more antioxidant properties than the control sample, it did not differ significantly from the control sample. Qualitative and health properties were selected as the superior treatment. The results of this study showed that the ethanolic extract of aloe vera gel can be used as a natural antioxidant instead of conventional synthetic antioxidants in the oil industry and to prevent oxidative spoilage of the oil in a desirable way. Therefore, it might be employed as a natural antioxidant in foods, particularly those containing edible oils.
Shakiba Kianiani; Mohammad Javad Varidi; Mehdi Varidi
Abstract
Introduction: Meat and meat products contribute about 20% to human fat consumption. Fat is the main source of energy and the base of fat soluble vitamins. Besides, it improves cooking yield and water holding capacity, conserves taste and flavor of products and affects the emulsion stability, juiciness, ...
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Introduction: Meat and meat products contribute about 20% to human fat consumption. Fat is the main source of energy and the base of fat soluble vitamins. Besides, it improves cooking yield and water holding capacity, conserves taste and flavor of products and affects the emulsion stability, juiciness, costumer acceptability and structural and rheological properties of meat products. But Animal fat contains a relatively high amount of saturated fatty acids and cholesterol, which can increase the risk of cardiovascular disease, diabetes, cancer types and obesity. Thus, the meat industry is interested in merchandising fat-reduced meat products without neglecting the positive effects of fat on flavor and texture.
Various researches have shown that the substitution of fat on a polysaccharides base such as fibers, starch, gums, and gels have improved and modified the texture, residual moisture and freeze stability, and decreased the price of the products.
Aloe vera leaf gel contains about 99 – 99.5 % water and 1 - 0.5 % of the total solid content. On dry matter basis aloe vera gel consists of 55% polysaccharides, 17 % sugar, 16 % mineral, 7% protein, 4% lipids and 1% phenolic compounds (Lawless et al., 2014). The most important carbohydrates of aloe vera gel are the long chain polysaccharides, comprising glucose and mannose, known as the glucomannans [β (1, 4) – linked acetylated mannan]. All the solid content of aloe vera gel are surrounded by polysaccharide mucilage layer.
Literature review pointed out there have been little investigations into the functionality of aloe vera gel in the emulsion meat products. According to the importance of producing low - fat meat products from one hand as well as the nutritional values and health characteristics of aloe vera gel on the other hand, this study was designed to replace the fat with aloe vera gel in the production of low - fat German sausage.
Material and Methods: Sausage samples containing 40% of red meat (German sausage) were produced based on the conventional plants formula. animal fat and vegetable oil replaced by 0, 50 and 100% aloe vera gel in the German sausage formulation. All samples were cooked at 90°C temperature to achieve the core temperature of 70° C, followed by cooling, they were kept in the refrigerator (4°C) until the subsequent experiments. The AOAC (2000) methods were used for measuring the moisture content, the amount of fat, ash and protein. The amount of carbohydrate was calculated based on the calculation of the total weight difference from the sum of ash, protein, fat and moisture (according to the method FAO / WHO). The amount of energy was computed based on the total amount of energy from fats, proteins and carbohydrates. To measure the pH of samples by pH meter, method of choe et al (2013) was followed. The color analysis was done on the surface of sausage cuts by chromometer. The parameters of color include L* (lightness), a* (redness) and b* (yellowness) were measured. Texture parameters include hardness(N), cohesiveness, springiness (cm), gumminess (N), chewiness (N.cm), adhesiveness were determined by texture analyzer as described by Bourne (1978). The sensory attributes were evaluated by 10 trained panelists. A five-point hedonic scale rating (1= very bad, 2=bad, 3= neither bad nor good, 4= good, 5= very good) was carried out.
Results and Discussion: Physicochemical properties analysis indicated significant differences among meat products (p ≤.0.01). The addition of aloe vera gel resulted a decrease in fat percentage and amount of energy, an increase in moisture and carbohydrate, but the amount of pH, protein and ash content did not change. This study showed that reducing the fat content and replacing by aloe vera gel caused a significant difference in the amount of energy (p≤.0.01).With respect to the significant contribution of fat in the production of energy, the amount of energy was reduced as expected by reducing the fat of the formulation. The results indicated that the value of L * showed the negative and positive trends with animal fat and vegetable oil changes, respectively (p≤.0.01). b* decreased by reducing the amount of fat and oil (p≤0.01), but the value of a* always remained constant (p˃0.05). The presence of aloe vera gel in sausage caused a reduction in hardness, adhesiveness and gumminess (p<0.05), while it did not affect the amount of adhesiveness and cohesiveness of samples (p˃0.05).
The substitution of fat with aloe vera gel had a significant effect on the sensory characteristics of German sausage (p≤.0.01). By reducing fat and oil and adding aloe gel to the German sausage formulation, color acceptance score was decreased. In terms of panelists, the blank sample had the best color and the fifth sample color had the lowest score. Juiciness of the samples was increased by increasing the amount of gel. The results also showed that the fifth sample received the maximum score of juiciness. Sausages smell acceptance negatively changed by reducing the fat content and adding aloe vera gel. Third and fourth treatments got the highest texture score. Also, the third sample had the highest scores for taste and general acceptance. Chewiness analyzing showed that by increasing the amount of fat replacement the rate of this factor decreased. as well as the maximum rate of chewiness was related to the blank sample.
