Effect of sodium alginate, carrageenan and hydroxypropyl methylcellulose hydrocolloids added to predust of breaded shrimp on chemical composition and sensory properties

Introduction: By definition, value-added products are a set of products that are prepared from raw food using various kinds of human or mechanical processing, which are different from their raw food in terms of shape, texture, taste, and smell. The battered and breaded products are among the value-added products, which constitute a wide part of the market for ready-to-eat foods. As indicated by the volumes of international trade in these products, the taste and convenience of preparing these products are favored by most consumers (Venugopal 2006). Breaded shrimp is a product that is first fried in oil after coating (predusting, battering and coating with breadcrumbs), and then it is packaged and stored after freezing. Thus, the consumer only accomplishes the final cooking step, which includes frying in the oil. The poor adsorption of the coating at the food surface leads to a sharp drop in the quality of the product. So, the predusting step is performed to prevent this problem. Predusting involves the use of a soft and dry substance that is applied to the wet surface of the food before further coating, and it reduces the gaps between the coating and the food surface and it can be used as a good flavor carrier by adding spices to it (Albert et al., 2009). The battered and breaded products absorb oil equal to 15-30 percent of their own weight during the initial frying process. Consequently, it has caused the consumers to be concerned about their health, obesity and cardiovascular condition due to the high amount of oil in these products. These concerns can negatively affect the battered and breaded products’ marketing (Venugopal 2006). The ability to form hydrocolloid gels, along with their natural hydrophilic properties, enables them to prevent the absorption of oil into battered and breaded products (Fiszman and Salvador 2003; Sanz et al., 2004; Akdeniz et al., 2006; Chen et al., 2008). For example, Pawar et al. (2014) evaluated effects of hydrocolloids including HPMC, carboxymethyl celluloses and xanthan on the oil uptake of kachori in deep frying. Due to the importance of reducing oil absorption and maintaining the quality of breaded products in public health, this study has examined the effect of sodium alginate, carrageenan and hydroxypropyl methylcellulose hydrocolloids in the composition of predust of breaded shrimp on chemical compounds and sensory characteristics.
Materials and methods: To prepare the breaded shrimp, the frozen shrimps were taken out of the freezer, two hours before being used and defrosting was performed in the air. Wheat flour was used in the initial predusting phase. The batter was prepared according to the formula of Fiszman and Salvador (2003), which contains 75% wheat flour, 24.5% corn flour, and 0.5% salt. The dry ingredients and water were mixed in a ratio of 1 to 1.4 for 3 min by using a blender and the breadcrumbs were used for making them breading. To prepare the breaded shrimp, the samples were first predusted and then battered in each treatment, and after dripping the extra batter for 30 seconds, they were ultimately coated with breadcrumbs. Once the coating was accomplished, the samples were fried in sunflower oil in a fryer at 190 ºC for 30 seconds by using a deep frying method so as to keep the product in shape. Then, in order to remove the extra oil, the samples were suspended for 2 minutes, and after cooling the samples to the ambient temperature, the replicates of each separate treatment were packed in zip lock packages and stored in a freezer at -20 ºC until the experiments were performed. After frying of each treatment, the oil was changed and the inner frying pan was washed and completely dried to fry the next repetition. All experiments were performed in 3 repetitions. 10 different treatments, including replacement of 0.5, 1, and 1.5% of hydrocolloids with the initial amount of wheat flour in the batter formulation were prepared. AOAC (2000) method was used to measure the moisture and ash. The amount of protein and fat was also calculated by using Parvaneh method (1377).  The sensory assessment, including color, odor, taste, texture, appearance, and overall acceptance, were applied by 10 trained examiners (students of the food industry within the age range of 20-23). For sensory evaluation, a five-point hydraulic system (5: very good, 4: good, 3: medium, 2: bad, 1: very bad) was used. The examiners were asked to rinse their mouths with water after eating each sample. Means were compared with an analysis of variance (ANOVA) followed by Duncan test to determine among means at p < /em>≤ 0.05 level.
Results and discussion: The findings indicated a significant difference between the treatments (p < /em><0.05). By evaluating the findings related to the results of chemical compounds (moisture, ash, fat and protein), the treatments associated with various levels of sodium alginate can be considered as treatments that have the best performance in maintaining moisture and reducing fat. Protein in the samples containing carrageenan had the highest value and the control had the lowest value. Also, the highest and lowest ash levels were belonged to different levels of sodium alginate and carrageenan, respectively. Evaluation of sensory indices (odor, taste, shape, texture, color, and overall acceptance) indicated that there was no significant difference between treatments (p < /em><0.05).
Conclusion: In general, according to the results of chemical compounds and sensory evaluation of the treatment, 0.5% sodium alginate is presented as the most suitable treatment for adding to the predust of breaded shrimp. In the end, after sodium alginate treatments, the results of 1.5% carrageenan and 0.5% hydroxypropyl methylcellulose had proper and not very good and significant performance, respectively.