Study Of Changes Of The Qualities Of Cookies During Shelf Life And Improvements Of Formula

Soft cookie is a kind of baked food between cake and biscuit. It tastes larruping. It is loved by many customers. This paper studied the changes and improvements of the qualities of soft cookies during the shelf life.The texture characteristics of fresh soft cookies were determined by TPA. It was found when the storage time prolonged, hardness, adhesiveness and chewiness increased rapidly, springiness, cohesiveness and resilience decreased, and the taste became worse. After compared with sensory assess, it was found soft cookie tasted delicious when hardness was under 1000g, the absolute value of adhesiveness was less than 10, cohesiveness was more than 2.0, resilience was more than 0.04, chewiness was less than 150. Springiness had little relation with the taste of soft cookie. There were remarkable correlations between sensory and instrumental parameters.Using spread ratio, color and hardness as targets, the effects of different emulsifiers, starch and gums on the qualities of soft cookie were studied. Single factor experiments indicated: the effects of different emulsifiers on color and hardness of soft cookies were obvious, the effects of different starch on spread ratio and hardness of soft cookies were clear, and the effects of gums on the three parameters were great. Three factors and three levels center compounding experiment, taking synthetical point as target, by using Response Surface Methodology, indated: basing on flour, the qualities of soft cookie could be improved observably by adding 1.17% mixed 2:1 distilled monoglyceride and sodium stearoyl-2-lactate, 6.62% pregelatinized cassava starch and 0.92% xanthan. The storage experiment of the soft cookies sealed and storaged at the room temperature for 270days indicated: moisture of soft cookies sealed during the storage time decreased from 9.99% to 7.82%, and water activity decreased from 0.693 to 0.637. The color became different during the first 30 days, and then it became more remarkable. L* and b* increased, while a* decreased. The changes of texture were obvious. Hardness increased and remained under 1000g until 150 days later. Cohesiveness decreased and changed most quickly during the first 30 days. 79 kinds of volatile flavor compounds were checked in soft cookie, including 8 aldehydes, 17 alcohols, 10 ketones, 7 esters, 12 hydrocarbons, 6 acids, 10 furans, 6 pyrans and 3 nitrogenous compounds. Aldehydes, ketones and esters gave the most contributions to the flavor. The contents of compounds which brought nice flavor reduced with the time extending, while bad flavor compounds appeared gradually, which made the flavor become worse later. The biggest peroxide value was 6.69meq/kg, and the biggest acid value was 0.7mgKOH/g. Both of them accorded with the country standard.