Effects of emulsifiers on processing characteristics and sensory quality of frozen spring roll wrapper

Abstract: Spring roll is a kind of convenient and delicious traditional Chinese snacks, which is widely consumed by consumers both domestic and abroad. With increased consumption and application of technology, freezing is also used for spring roll production. However, there are a number of problems left to be solved on quality of frozen spring roll, such as the cracking in wrapper caused by water lost, being not crispy enough after fried, the filling splashing out during frying. In order to improve the quality of spring roll and explore the effects of emulsifiers on qualities of frozen spring roll, glycerol monostearate (GMS), sucrose fatty acid ester (SE), sodium stearoyl lactylate (SSL), diacetyl tartaric acid esters monod and diglycerides (DATEM) and lecithin were chosen for further investigation. The changes of slurry viscosity over time, weight loss rates of spring roll wrapper in the period of frozen storage and sensory quality of fried products were evaluated. To understand the mechanisms of emulsifier on processing characteristics, the tensile properties of fresh and frozen wrapper were also determined by texture analyzer. The results showed that the addition of emulsifier could enhance stability of the slurry viscosity during the freezing time compared to the control, and combined with the requirements of actual production, the optimum addition of the five kinds of emulsifier are 0.3%, 0.3%, 0.3%, 0.2% and 0.2% respectively for GMS, SE, DATEM, SSL and lecithin. Frozen storage process was always accompanied by a loss of water, and water loss rate of the control spring roll wrapper was up to 17.1% after 1 month freezing. Emulsifier could significantly reduce water loss rate during the freezing storage (P<0.05), and GMS had the best effect, followed by 0.2% SSL and 0.3% SE, but 0.3% DATEM and 0.2% lecithin had poor water retention. For the hardness of spring roll wrapper, after 1 month of frozen storage, the hardness of control samples increased by 427% compared with fresh ones, while the average hardness of the samples added with emulsifiers only increased by 137%. This result showed that the emulsifier could significantly inhibit the negative effects of freezing (P＜0.05), especially for GMS and lecithin. And GMS could also significantly enhance the maximum tensile resistance of the spring roll wrappers, increased by 102% compared to control sample. Except for GMS, the other four kinds of emulsifiers had certain improvement effects on hardness and tensile properties of spring rolls wrapper during the frozen storage. In general, GMS had the best effect on water retention, and it could greatly slow down the deterioration of hardness and tensile properties, lower weight loss rates and thus optimize the quality of frozen spring roll. In terms of sensory evaluation, GMS also had positive effects on improving uniformity of surface color and external shape, and had no significantly negative effects on flavor of the products. Addition of emulsifiers showed different aspects to improve the quality of frozen spring roll wrapper. The results provide the theoretical basis for the emulsifiers widely applied to the frozen spring roll products.