| The uptake of dietary fiber, which is importantly related to diet balance, has attracted a lot of attentions. The addition of dietary fiber in staple and snack foods corresponding to the requirement of customer on nutrient enrichment is popular. As a tradition aquatic crop in China, lotus seed(Nelumbo nucifera) effectively promotes the growth of local economic and famer income by the way of fresh marketing and processing. However, lotus seedpods as the main by-product are mostly discarded and burned, resulting in resource waste and environmental pollution. The development of lotus seedpod is meaningful for the increment of lotus seed industry, the growth of famer income and the protection of environment. As one of the main nutritional ingredients in lotus seedpod, dietary fiber has been systematically studied on preparation, modification and application, and the relative results and conclusions are as follows.1. Technology optimization of enzymic preparation of crude dietary fiber from lotus seedpod(LSDF) by response surface methodology. The weighted value of starch hydrolysis degree and protein hydrolysis degree was used as the evaluation index for technology optimization. Based on the results of single factor test, the enzymic preparation technology of crude LSDF was optimized by response surface methodology. The regression analysis indicated that the impacts of various factors on the evaluation indexes, including starch hydrolysis degree, protein hydrolysis degree and weighted value, could be ordered as pH value > hydrolysis time> solid-liquid ratio> enzyme dosage. The optimal parameters were composed of liquid ratio 1:16,pH value 5.4, enzyme dosage0.3% and hydrolysis time 65 min. Under these conditions, the hydrolysis degrees of starch and protein were 74.83% and 34.26%,respectively.2. Formula optimizations of noodle and biscuit enriched with LSDF.(1) The formula of noodle enriched with LSDF was optimized by single factor test and orthogonal test using the evaluation index weighted from sensory score, cooking yield and water absorption ratio. The results indicated that: the impacts of various factors on the cooking yield could be ordered as crude LSDF addition percentage > salt addition percentage > water addition percentage; the impacts of various factors on sensory score, water absorption ratio and weighted value could be ordered as salt addition percentage > crude LSDF addition percentage > water addition percentage.The optimized formula of noodle was composed of 3% crude LSDF, 0.5% salt and38.5% water, and could result in the color, flavor and texture of product were all preferable.(2) The formula of biscuit enriched with LSDF was optimized by single factor test and orthogonal test using the evaluation index of sensory score. The results indicated that: the impacts of various factors on the sensory score of biscuit could be ordered as crude LSDF addition percentage > fat addition percentage > osteoporosis agent mixture ratio. The optimized formula of biscuit was composed of 6% crude LSDF, 27.5% fat and sodium bicarbonate-ammonium hydrogencarbonate ratio 5:2,and resulted in the biscuit with chocolate, moderate sweetness and crisp taste.3.Technology optimizations of homogenization and high-temperature modification of LSDF by response surface methodology. The soluble dietary fiber yield was used as the evaluation index to optimize the modification technology by single test and response surface test. Regression analysis indicated that the impacts of various factors on the index could be ordered as homogenization speed >homogenization time > solid-liquid ratio, as well as treatment temperature > treatment time > solid-liquid ratio. The optimal parameter for homogenization modification were homogenization speed 19000 r/min, homogenization time 8 min and solid-liquid ratio of 1:19.5, and for high-temperature modification were treatment temperature115 ℃, treatment time 40 min and solid-liquid ratio 1: 6.75. Under these conditions,LSDF obtained 5.44% soluble dietary fiber after been treated with homogenization,and obtained 4.33% soluble dietary fiber after been treated with high-temperature.4. Physicochemical properties of LSDFs and their effects on the quality of noodle and biscuit.(1) The physicochemical properties of LSDF and its modified derivants including homogenization-treated LSDF-1 and high-temperature-treated LSDF-2, were comparatively analyzed. Both the two modification methods could significantly increase the swelling rate and water retention ability of LSDF(P<0.05);high-temperature treatment obviously decreased the oil retention ability of LSDF(P<0.05), but strengthened the sodium cholate adsorption ability(P<0.05);homogenization treatment showed no significant effect on the ability if oil retention and sodium cholate adsorption(P>0.05). The layered microstructure of LSDF was changed by homogenization treatment, from compacted to scattered.(2) The effects of LSDF on noodle quality was investigated by texture and electronic tongue analyses.Compared with the control, crude LSDF, LSDF-1 and LSDF-2 all did not change the textural features of noodle at the addition percentage of 3%, and also did not change the chewiness and elasticity(P>0.05). Crude LSDF could increase the bitterness,astringency, aftertaste-B and savory of noodle, in which bitterness and savory were obviously weakened by modification. The increasing addition(from 3% to 5%) of LSDF-2 showed no significant effect on noodle texture(P>0.05), but markedly increased the bitterness and aftertaste-B. The increasing addition(from 3% to 5%) of LSDF-1 could significantly increase the stalemate and hardness(P<0.05), but had no effect on taste.(3) The effects of LSDF on biscuit quality was investigated by texture and electronic tongue analyses. Compared with crude LSDF, both LSDF-1 and LSDF-2 could increase the hardness and crisp of biscuit. Crude LSDF could strengthen the bitterness, astringency-B and savory of biscuit, in which bitterness was obviously weakened by modification. The increasing addition(from 6% to 10%) of LSDF-1 and LSDF-2 did not significantlu change the hardness and crunchiness of biscuit(P>0.05), but obviously increased the bitterness and astringency.Lotus seedpod, which is recorded in "People’s Republic of China Pharmacopoeia", is relative safety as a raw material for the development of dietary fiber. After been prepared and modified, LSDF can be added into noodle and biscuit at the mass percentage(relative to flour) of 5% and 10%, respectively. The high content of dietary fiber effectively enhances the biological functions of the products, and improves their textural and sensory qualities. This study provides a new way for the comprehensive utilization of lotus seedpod. |
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