The effect of Xanthan gum added to the coated breaded shrimp (Litopenaeusvannamei) on oil uptake, nutritional quality indices and sensory properties

Introduction: Value-added products, referring to the fact that a raw commodity or commodities are transformed into a processed product through use of materials and technology, may have different appearances, textures, tastes and smells than their raw material. Fried product is one of the most popular ready to eat foods all around the world. They have excellent sensory qualities due to their appealing flavor and texture. Products such as shrimp usually coated with breading before frying to induce additional sensory and quality attributes. The process of battering and breading provides special functions in food products, including improved appearance of the products, increased texture crispness, reduced oil uptake during the frying process and increased the shelf life of the coated products.Hydrocolloids are used extensively in food technology as thickening and gelling agents, stabilizers, and emulsifiers. In addition, the hydrocolloid coatings are of great interests due to their desirable barrier properties to gas/moisture and good mechanical characteristics. Thus, a variety of foods have been coated with hydrocolloids to prevent moisture loss, preserve texture, and maintain color, consequently extending the product shelf-life. Specifically, the hydrocolloid coatings are often known to reduce the oil uptake of fried foods. The mechanisms of the oil uptake during frying are associated with heat transfer from the frying oil to the food and the migration of water and oil. Various hydrocolloids have been tested as an oil barrier coating material and the effectiveness of hydrophilic and thermo-gelling hydrocolloids in reducing oil uptake during frying has been well reported in previous studies. Material and Methods: Fresh peeled shrimp (Litopenaeus vannamei) was purchased from Gomishan city, Golestan province, Iran. Xanthan gum was bought from Asia Research Petrochemisry (Iran). White flour, corn flour, breading powder, oil and salt were prepared from the local supermarket. All other chemicals used in this study had analytical grade and were gained from Fluka or Merck companies. The freezed shrimps were thawed at room temperature before processing. Four different formulations were applied in pre-dusting and battering as following:Control= without xanthan in pre-dust and batter,A=2% xanthan in predust,B=2% xanthan in batter,C=1% xanthan in predust + 1% xanthan in batter.The batter formulation was consisted of wheat flour (75%), corn flour (24.5%), salt (0.5%). The dry ingredients were blended for 3 min at speed 2 m/s in a Kenwood Major Classic mixer (Kenwood-BL460) with water (1:1.4 solid to water ratio). In each treatment, firstly, pre-dusting was done and then, battering. Afterwards, it was allowed to drip additional batter for 30 s. For final coating, orange bread crumbs were used (Gols Company). The samples were pre-deep-fried by sunflower oil at 190 °C for 30 s (Fritaurus Professional 3 domestic fryer, Barcelona, Spain). The treatments were cooled to room temperature for 30 min. Then, they were placed in plastic freezer bags (LDPE film, thickness 150 μ) and stored at -18 °C. Moisture content in the samples was determined in quadruplicate according to the Association of Official Analytical Chemists (AOAC) (2000) method. Fat content of fried products was distinguished using Soxhlet extractions according to the AOAC (2000) method No. 992.15.Batter pickups (%) were determined as following equation:Batter pickup (%) = (Weight of coated shrimp–Weight of uncoated shrimp)/(Weight of coated shrimp)×100Product yield (%) was calculated by weight of the cooked shrimp block/ weight of the raw shrimp block × 100.Quantitation of fatty acid methyl esters in raw and fried breaded shrimp was carried out by gas chromatography (Unicam-4600) with 30 mm×0.25 mm column (Film Tekness-0.22 μl) and FID detector, using glyceryl tritridecanoate (C13:0) as an internal standard (Sigma, Barcelona, Spain). Fatty acids were expressed as percentage of total fatty acid methyl esters or in absolute content (mg/100 g food).Fried shrimp coated with the selected formulations was evaluated by a trained sensory panel of 12 members. Each sample was randomly numbered and presented to the panel member. A hedonic panel was also performed by the same panelists, who evaluated aroma, taste, texture, color, appearance and overall acceptability characteristics. A hedonic 5-point scale was used, 1s unusable, 2s dislike, 3s acceptable, 4s like and 5s like very much. All data are reported as mean± standard deviations of triplicate. One-way analysis of variance (ANOVA) was used to compare the means of all evaluated parameters. Differences were considered significant at P