Studies On Mechanical Properties And Texture Evaluation Of Toughness Biscuits

As typical convenience foods, biscuits are popular among consumers, brittleness and crispness are very important texture,butthe main evaluation method of biscuits texture is sensory evaluation according to the available food industrial standards and national standards at present, although there are some equipment test reports at home and abroad, but they are not mature and have not formed a complete evaluation system, and the evaluation of brittleness is sound test method. So to establish equipment test method is very important. This thesis studied the instruments test method to evaluate brittleness of toughness biscuits, made correlation analysis of sensory evaluation and objective evaluation between different kinds of biscuits texture, and studied the texture changes of biscuits under different storage conditions. The main results are showed as followings:The results of biscuits texture difference through puncture test show that:the middle and edge with the same biscuit positive, the middle with different biscuits negative, the positive and negative with the same biscuit edge were significantly different, so it should be sampled in the same position.Test conditions of puncture test, three-point-bending test, and TPA test, which were used to study the brittleness were optimized. The results are that: three-point-bending test of the optimal conditions were:rate of 0.5mm/s, span 30mm, the elastic modulus of biscuits which were just opened was 12.6474x107N/mm2, Weibull modulus could be characterized brittleness of biscuits, the greater its value, biscuits were greater brittleness. The optimal conditions of TPA test were:30%compression, rate of 0.5mm/s, residence time of 5s. The optimal puncture test condition was 1.0mm/s rate, HDF/CFS support form, P0.25S probe, the rupturing distance was the one in the force-distance curve corresponding with the force was zero.By changing the moisture content, a contrast of puncture, three-point-bending, and TPA test methods show that:puncture method was superior than the other two methods, the correlation coefficient R2 between Nsr and moisture content was 0.9763, so Nsr could characterize brittleness of biscuits. The correlation analysis of Nsr, the distance corresponding with the max force, the brittleness value and the sensory evaluation of nine kinds of biscuits show that, Nsr was the first factor to the stepwise regression equation of sensory brittleness evaluation, the next was the distance corresponding with the max force, which had verified that puncture test was best.If all four methods were tested, the sensory evaluation indicators could be replaced by the index test equipment, the model correlation coefficient were above 0.996. Sensory evaluation of cohesion could be predicted not only by TPA test but also by three-point-bending test, the other indexes could be predicted by TPA test. If only tested by the best method, the model correlation coefficient were all over 0.97 except the elasticity which was 0.927.The texture of biscuits during storage showed that:the environment temperature and humidity had a significant effect on the biscuits texture, and the humidity was greater than temperature. The best storage conditions for temperature was 18℃, humidity was 50%. Expected model of storing biscuit was used by BP neural network forecast model, the correlation coefficient of max force, Nsr, and Fm of puncture test, the distance corresponding with the max force of three-point-bending test were high, while the TPA indexes were bad. So these three indicators of puncture test could be used to predict 50% humidity, different temperature and humidity over 65% of early storage (5h ago) biscuits texture changes, but the distance corresponding with max force of three-point-bending test to predict more than 65% humidity in the later stage of storage (5h after) biscuits texture changes.These research results will provide a new objective method for the evaluation of biscuits toughness, theoretical foundation and practical application were also built up for mechanical texture evaluaton and production process, quality inspection, packaging, transport and storage of biscuit.