Study On The Processing Technology Of Instant Full Lotus Root Powder High In Resistant Starch

Lotus root is of high dietary and medicinal values due to the fact that it is rich carbohydrates,protein,vitamins,dietary fiber and other substances which are beneficial to human health.The lotus root starch is the main kind of powder for lotus root currently sold in the market.Unlike the starch,the processing of whole powder maximizes the retaining of nutrition and keeps the unique aroma,flavor,texture and nutritional values of lotus root.Resistant starch in the whole powder is a prebiotic which may increase the proliferation of beneficial bacteria and promote the balance of microflora in human colonic environment.Increasing the content of resistant starch will effectively improve the nutritional value of full lotus root powder.In this paper,we studied the Fujian aquatic vegetable Lotus root with the application of sulfur-free color protection technology on fresh-cut slice and investigated how different drying methods affect the drying outcomes and the resistant starch content of the whole powder.Furthermore,we made comparisons between lotus root starch and full lotus root powder high in resistant starch of their physic-chemical properties with the methods of Scanning Electron Microscope(SEM),Brabender Viscometer,Differential Scanning Calorimetry(DSC),and Rheometer.Based on the quality requirements for full lotus root powder,we investigated the processing technology of sugar-free instant full lotus root powder high in resistant starch.The main results were as follows:(1)Study on applying the technology of sulfur-free color protection on fresh-cut lotus root slicesWe compared the effects of different color fixatives and their concentrations on the color protection of fresh-cut lotus root.The optimal combination for color fixatives was determined to be:0.35%phytic acid,0.3%citric acid,and 0.3%ascorbic acid with processing time of 10min.Within the optimal processing time,fresh-cut lotus root exhibited the bright while color without browning occured.Compared with sulfur treatment,sulfur-free treatment demonstrated an equally efficient but safer way in the color protection of lotus root slices.(2)Study on the effects of drying methods on the general quality of full lotus root powderWe compared freeze drying,spray drying,and roller drying in the drying outcomes.The results suggested roller drying delivered the best quality.We studied the roller drying process and optimized the parameters with orthogonal experimental design.The parameters were optimized as:roller steam pressure 0.4MPa,roller speed 1.5 rpm,flow rate of feed mass 50 kg/h,the rehydration of full-lotus root powder 3.93.Under these conditions,the content of resistant starch was 11.23%.To improve the content of resistant starch in full lotus-root powder,we studied the effects of enzyme-roller drying on the yield of resistant starch.The orthogonal experimental design was applied to optimized the drying parameters with the results as:Pullulanase's action temperature 65?,pullulanase's action pH 5.5,pullulanase's action time 17h,pullulanase's action dosage 5U/g.Under these parameters the average yield of resistant starch reached 22.86%and was 103.6%higher than that without enzyme-roller.(3)Comparative studies between full lotus-root powder high in resistant starch and lotus root starch on the physicochemical propertiesIt has been shown that the pastes of lotus root starch and full-lotus root powder high in resistant starch were both non-Newtonian fluids.Compared with the starch,the full powder high in resistant starch had a smaller value in yield stress ?0,consistency coefficient k,degree of shear thinning,and thixotropic loop area,wherease the opposite trend appeared in the resilience of shear structure.The results indicated a higher concentration of the starch paste was associated with a more rigid and elastic three-dimensional network of gel,which could lead to difficult recovery after shearing.The gelatinization enthalpy of lotus root starch was higher than that of full lotus-root powder with high resistant starch,suggesting the energy consumption of high-resistant-starch powder during gelatinization was higher than that of intact lotus root starch.The initial temperature of gelatinization for full lotus-root powder high in resistant starch was lower than that of lotus root starch,with a better gel performance in the latter.These evidences indicated a better performance of gelatinization and thermal stability for full lotus-root powder than the starch.The full lotus-root powder high in resistant starch demonstrated a promising potential in the application of food processing due to its convenience in blending and reconstitution with a better degree of gelatinization.(4)Study on the processing technology of sugar-free instant full lotus-root powder high in resistant starchWe studied the formula of sugar-free instant full lotus-root powder and obtained the optimal results by adding 20%maltodextrin and 3%healthy sugar(L-arabinose:sucralose = 6:4)during reconstitution,which led to a crystal clear,lubricating-taste paste in moderate sweetness with the scent of lotus root.To improve solubility,we studied the technology of extrusion-granulation with results showing a positive association between the granulation time and the particle diameter of full lotus-root powder.At the granulation time of 900s,the diameter of particle reached around 1.5mm which better meets the needs of the product.With extrusion and granulation,the surface of full lotus-root powder became a loose,mesh and porous structure with better moisture absorption and solubility.The technology improved the product quality with resistant starch reached a content of 15%.