Modification Of Dietary Fiber From Fermented Vegetables And Its Application In Edible Wrapping Paper

Nowadays,with human diet becoming more and more refined,the importance of dietary fiber having physiological activities such as preventing obesity and regulating intestinal function is more prominent in the maintenance of human health.Having unique flavor,traditional fermented vegetables enjoy a great popularity among consumers.However,there are many problems in the production process,such as long fermentation cycle and high nitrite content,which restricts their industrial development.Meanwhile,fermented vegetables,rich in dietary fiber though,lack intensive development and utilization.Therefore,this study improved the traditional fermented vegetables preparation process by using ultra-high pressure pretreatment and complex bacteria low-salt fermenting,and obtained low-nitrite products rich in high-quality dietary fiber.The influence of the new process conditions for dietary fibers'structure,quality and function in fermented vegetables were also explored in this study.Finally,the fermented vegetables prepared by the improved process were further developed into edible wrapping paper through wet-forming process.Provide with nutritious and practical functions,this new products break the traditional fermented vegetables product form.The results of the research are showed as following:1.On the basis of the traditional natural fermentation process,the ultra-high pressure treatment process is added,and two kinds of fermenting strains,Pediococcus and Lactobacillus plantarum,with strong degradation of nitrite and acid production ability,are introduced for compounding low-salt fermentation,in fermented vegetables.A new process of kimchi products with high quality dietary fiber was established by single factor experiment and orthogonal experiment,using dietary fiber,nitrite component content and p H value of fermentation endpoint as evaluation indexes.The results showed that,when treated with ultra-high pressure of 400 MPa for 15 min,and 0.03%of the composite fermenting agent(1:6 for the ratio of Pediococcus and Lactobacillus plantarum)was inoculated at 25°C for 5 days,the products were in good quality.Specifically,the nitrite content of the product prepared under the optimized process conditions was 0.0030 mg/g,which was significantly lower than the national standard,and the IDF/SDF(insoluble dietary fiber/soluble dietary fiber ratio)was 2.44,indicating that the dietary fiber composition of fermented vegetables was reasonable and the quality was good;2.The physicochemical properties,physiological functions and structures of the dietary fiber in the fermented vegetables prepared by the optimal process,the superior process and the natural fermentation process were compared.The results showed that,after the ultra-high pressure-complex bacteria low-salt fermentation process,the water-holding capacity and expansion force of IDF from the optimally prepared products were significantly increased by 24.25%and 46.24%,respectively,compared with the natural fermentation,the oil holding capacity were decreased 45.82%though;the heavy metal adsorption capacity,cholinate adsorption capacity?-amylase activity inhibition ability and cation exchange capacity were significantly improved(p<0.05),and the adsorption capacity of Pb and As was increased by 1.30 times and 4.00times.The adsorption capacity of sodium and sodium taurocholate increased by 33.11%and 50.83%,the inhibition ability of?-amylase activity increased by 91.83%,and the cation exchange capacity increased by 3.54 times.The solubility of SDF prepared by the optimal process was increased by 9.87%.The ABTS~+·and DPPH·radical scavenging enhancements were increased by 5.50 and 1.05 times,respectively,but the reduction of iron ions was reduced.Furthermore,the IDF structure of fermented vegetables was analyzed by monosaccharide composition,infrared spectroscopy,X-ray diffraction and scanning electron microscopy.The results indicated that the new process did not change the crystal form of IDF from fermented vegetables,but its characteristic diffraction peak width increased,the height decreased.There was also a downward trend of the crystallinity,indicating a dispersion phenomenon;the microstructure is looser,the surface pore diameter was increased,and the grain refinement degree was increased.These structural changes explained the mechanisms of their physical and chemical properties and functional changes;3.The formulation development of fermented-vegetables based edible wrapper were carried out by single factor and compound orthogonal experiment,selecting from 4 kinds of thickeners(pectin,potato starch,soy protein,CMC-Na)and 3 plasticizers(glycerin,sorbitol,citral).Whereafter,optimization of production process including drying temperature,drying time,homogenizer speed,degassing parameters and other process conditions were studied by single factor and orthogonal experiments.Evaluation indexes of products including thickness,basis weight,tightness,transparency,colors,water content,water solubility,oil permeability,tensile strength and elongation at break were determined,and analyzed with multi-index evaluation method based on chromatographic analysis to obtain optimal formulation and process parameters.The comprehensive score of fermented-vegetables-based edible wrapper prepared under the optimal process conditions was 703.2,which was higher than the score of the product not optimized by the whole formula(598.5).The product obtained under the optimum process had a good overall quality with a suitable thickness,excellent flexibility and strength(elongation at break of8.91%,tensile strength of 6543N/m)good storage performance(water content of 9.21%)and fresh color.