A Study On Determination Of Texture Characteristics Of Cereal Foods

Rice, steamed bread and bread are our main staple food in china, the eating quality were tested by sensory evaluation. Sensory evaluation is not only hard sledding and time consuming but also easily affected by personal preference and individual factor, and the objective, reliableness and comparability of evaluation results are poor. Food texture analyzer, an accurately quantizing measuring instrument, can accurately quantitative the food texture characteristics and probability instead of sensory evaluation. Food texture determination is widely applied in the study of food texture characteristics and quality evaluation, but the related determination standard methods are few and the contents and results and of different methods have a poor comparability and reference value. The research studies the production method and determination conditions on the stability of measured values, reference to the related national standards of food sensory evaluation and international standards of texture determination through sample making and texture determination experiment, we get the optimum production method and determination conditions and lay a foundation for food texture determination method. The research contents and results are as follow:1. The texture characteristics of bread made of different flours were determined by a food texture testing machine, according to the standard AACC method 74-09, in order to investigate methods of bread making and the dispersion and concentricity stability of bread hardness and the impact of storage time, slicing method, testing location, environmental temperature and humidity degree of compression and crosshead speed on determination of the bread hardness; we get the optimum production method and determination conditions. The results show that:the optimum production method and determination conditions are one group of five breads (25mm×15 slices) stored 1d,50% compression,100 mm/min crosshead speed and hardness value of 25% compression; the bread hardness values increase gradually when the testing location move downward, the average hardness variation of the upper and middle part of a bread is little, the best testing location upper and middle part; the influence of the bread production and the environmental temperature and humidity on the bread hardness determination are great, the relation is y= 1.3191x2-74.859x+1429.7, the optimum environmental temperature is constant ordinary temperature (20℃±=0.5℃) and ordinary humidity (45%-85%).2. This experiment measured the texture characteristics of steamed bread made of different quality types of flour reference to GB/T 20571-2006 according to TPA model with a food texture analycer, in order to investigate methods of steamed bread making and the dispersion and concentricity stability of steamed bread hardness and the impact of storage time, slicing method, testing location, environmental temperature and humidity degree of compression and crosshead speed on determination of the steamed bread hardness; we get the optimum production method and determination conditions. The results show that:the spectrum characteristics (three stage feature) from different kind of steamed breads are similar, and the correlation between the measured values of hardness and flour quality is obvious. One group of two breads (6 slices) and the cocefficient of variation of the measured texture values (hardness, springiness and cohesiveness) in the steamed bread is between 1.37～8.07%, the stability of the hardness measured value is significantly better than that of other two. The environmental temperature and humidity of fabrication, storage and determination had great influence on the steamed bread hardness value, the higher the temperature, the smaller the hardness value, the influence of slicing and measuring is significantly better than storage (cooling); the hardness value in upper parts was smaller than lower parts, the change was 7.2g/mm in vertical surface. The optimized conditions are:50% compression,60 mm/min crosshead speed,60min storage time,20℃ environmental temperature of fabrication and measurement.3. This experiment measured the texture characteristics of cooked rice made of different quality types of rice reference to GB/T 15682-2008 according to TPA model with a food texture analycer, in order to investigate methods of cooked rice making and the dispersion and concentricity stability of cooked rice hardness and the impact of storage time, slicing method, testing location, environmental temperature and humidity degree of compression and crosshead speed on determination of the cooked rice hardness; we get the optimum production method and determination conditions. The results show that:the influence of the size (form) of plunger on texture determination whether it can reflect the eating quality is great; the stability and accuracy of measured hardness values were better than adhesiveness, it was adapt to be the main index of determination of texture characteristics of cooked rice on the conditions of sample cooked rice made by electric rice cooker and then pressed down 8mm, determined by Φ 25.4mm spheroidal plunger; the decreasing tendency of hardness values of cooked long rice is obvious with the extension of storage time, hardness values of cooked round shaped rice increased slowly within 12h. The influence of temperature of production, storage and determination on cooked rice hardness values is great. It was suggested that the temperature of production, storage and determination be constant. The optimum conditions are:90min storage time,50% compression,60 mm/min crosshead speed, 20℃ temperature of production and determination.