Study On Quality Evaluation And Process Technoloof Chinese Hard Peanut-Candy

In recent years, Chinese traditional peanut candies are favored by consumers for thecrispy and fragrant taste. Unfortunately, some quality problems occurred frequently becauseof the small-scale production, lack of standerlized evaluation criteria system and peanuroxidation. In this study, peanuts were used as raw materials. According to the specific stepsthe factory suggested, the traditional roasting parameters, combined heated treatmentparameters and the quality of the boiled syrup and the oxidation of the peanut candy werestudied. The sensory evaluation system and the prediction models of shelf-life were alsoestablished. All of this can determine the optimum processing parameters and delay therancidity process of the samples, and will guide the actual operation of some plants.1. In order to study the changing rules of the peanut qualities during roasting, the paperinvestigated the effects of different temperatures(90℃、120℃、140℃、160℃、180℃) on therelevant drying characteristics, colours, textures. Results: The drying character curvesfollowed the Page model (R2≥0.95) better than the two-parameter exponential model and themodel parameters (n&K) fit the quadratic model. At the initial period of roasting, the gradualincrease in the L-value was observed.After that, L-values continuously declined. In themeantime, continuous decline in a and b values and rise in BI were observed. With the fittingof zero-or first-order kinetics and polynomial models, the L-values turned out to follow thecubic polynomial model best (R2≥0.98, at different temperatures). The fitting of kinetics andpolynomial models showed that the crispness followed the first-order kinetics best (R2≥0.98).2. In order to advance the edible qualities and storage stability, the combined heatingtreatment was adopted. The four influencing factors including toasting temperature, toastingtime, hot-air drying temperature and hot-air drying time were optimized with Box-Beckenresponse surface analysis. According to the analysis, the model could express the relationbetween sensory evaluation scores and the processing factors. The optimum conditions were:toasting temperature at130℃, toasting time for30min, hot-air drying temperature at90℃and hot-air drying time for40min. In the optimum conditions, improvement of colour andoxidation stability was observed while the water content of the end products stayed similar tothose traditional processed.3. In order to exploring the rule of changes in syrup, Aw, colour, hardness, stickness andsensory values were studied at different ratio of sucrose/maltose. The results showed: Duringthe boiling process, the Aw decreased with the concentration increasing.After theconcentration reach90%, the Aw went below0.7, which meaned the samples could meet the storage requirement. At the same time, the syrup became brown. Samples at different sucrose/maltose ratio all showed continuous increase of a-and b-value, while the Lvalue of sample atratio of5:1declined initially and then went up, which could be explained by crystallization.Cooled to the ambient temperature, the hardness of syrup increased with the concentrationand the proportion of sucrose. The stickness increased with the concentration at first and thenrapidly declined. The concentration and sucrose/maltose ratio affected the sensory valuessignificantly. The correlation of sensory values and instrumental indexes was also observed.4. Systematical study established the sensory evaluation system of peanut candy. Theinfluence of processing factors and the correlation between sensory evaluation andinstrumental indexes of peanut candy were also studied. Results: Based on expert grading andfuzzy ordering,8factors were selected out as the sensory evaluated items and the weightvalue of each item was deduced. The sensory evaluation system was established according tohundred-mark system. As for the influence on the instrumental indexes, Aw of thepeanut-candy mostly depended on the concentration of the syrup. The L-value wassignificantly influenced by the amount of peanut and the concentration of the syrup, while thehardness and crispness depended on the size of peanut.Similarly, according to ANOVA, thesignificance of influence on the sensory evaluation value followed the order: amount ofpeanut> size of peanut>amount of maltose> concentration of the syrup. In addition, thesensory evaluation results and instrumental indexes showed significant correlation.5. Oxydition during the storage and shelf-life prediction models of peanut-candy werestudied. Results: The lipid oxidation of peanut kernels had a value in direct proportion to themoisture content of sugar. The higher percentage of sugar can delay the lipid oxidation ofpeanut kernels. In addition, storage stability was affected by the crushing degrees of peanutkernels. In study of the storage conditions, two typical package of traditional peanut candywere adopted. The skin packing showed better anti-oxidation effects than the can packing atdifferent temperatures and humidity. During the storage, the POV and AV of peanut candyshowed good fits with the first-order kinetic model (R2≥0.95) and the kTgrowed up with theincreasing temperatures which followed Arrhenius equation. Based on the kinetic analysis,shelf life prediction models were deduced, with POV and AV as significant index, respectively.The prediction results were acceptable and effective by validation test with the relative errorless than10%.