Research And Application On Preparation Technology And Edible Film’s Forming Property Of Lotus-seed Starches Modified By Dry Heating

Lotus seed starch was a specific starch with high amylose content of more than40%, which suggested lotus seed starch has a potential prospect in development andutilization. As a new method to produce modified starch, the physical and chemicalproperties of starch can be changed by dry heat treatment in the presence of ionicgums. The preparation technology and characteristics of lotus seed starch modified bydry heating treatment with alginate were studied in this paper, the process offilm-forming was optimized also. Futhermore, the antimicrobial effect of modifiedlotus seed starch edible coating was experimented and coating was applied tofresh-cut dragon fruits storage. The results offer a scientific guidance for theprocessing and utilization of lotus seed starch modified by dry heating, a theoreticalbasis for the application of edible starch film in fresh-cut fruits storage was alsoprovided.1. The effects of ionic gum addition, pH, reaction temperture and time on thecharacteritics of lotus-seed starches modified by dry heating were studied and thepreparation parameters of modified lotus-seed starches were determined. The resultsshowed that lotus-seed starch dry-heated with alginate could improve thefilm-forming properties of lotus-seed starches, and pH and dry-heating temperturewere the most significant impact factors. The optimized processing parameters of dryheating modified lotus seed starches during the orthogonal experiment were ionicgum additions1.0%, pH7.0, reaction time3hours and temperture130℃. The idealproperties of starch were obtained in this conditon.2. The characteristics of granuler, pastes and film-forming after gelatinized oflotus seed starch modified by dry heating with or without alginatewere analyzed. Theresults showed that the effect of dry heating directly on the properties of lotus seedstarch was not significant. The lotus seed starch granule modified by dry heating withalginate elliptic shape mostly, few of them had slight crack on the surface, adhesivematters could be found on the surface of granules which sticked with each other.Modified lotus seed starch had higher solubility, lower swelling power and thetransparency of modified starch pastes was lower. Dry heating had no effect on thefreeze-thaw stability of lotus seed starch pastes, while could enhanced mechanicalproperty, improved water vapor barrier property and decreased the solubility of modified lotus seed starch based films. According to Brabender viscosity curve, thelotus seed starch modifed by dry heating with alginate had a lower beginninggelatinization temperature and peak viscosity, weaker thermostability, stronger coldviscosity stability and weaker retrogradation.3. The influence of modified lotus seed starch and glycerol addition and dryingtemperature on the characteristics of modified lotus seed starch film was studied andthe filming process was optimized using response surface methodology. The resultsshowed that the ideal properties of starch films were obtained when modified starchaddition at3.5%. It showed a decreasing in softness, thin and dry and easy breakingwhen the addition of glycerin was low. A decrease in mechanical property and anincrease in hydropjily and solubility were found when the addition of glycerinincreased to a certain extent, the edible film showed easier to get damp withincreasing glycerin addition, which got the highest index values when glycerinaddition was1.5%. The ideal properties of modified lotus seed starch film could notbe obtained when drying temperature was too low or higher, but the moderatelydrying temperature. The optimized processing parameters of modified lotus seedstarch film by comprehensive optimization was modified lotus seed starchconcentration3.53%, glycerol addition1.51%and drying temperature80.61℃.4. The antimicrobial properties of dry-heating modified lotus seed starch ediblefilms which been added different bacteriostatic agents and during different pHconditions were evaluated and the best antimicrobial parameters were determined.Then the modified lotus seed starch edible coating were applied to fresh-cut dragonfruit storage. It indicated that the edible coating could inhibit bacteria such asStaphylococcus aureus, Bacillus subtilis and mould such as Aspergillus niger,Penicillium significantly when the addition of Nisin and Natamytin were0.02%and0.06%respectively, pH value was6. The results showed that edible coating withantimicrobial agents could effectively decrease water and nutrient loss. Thesenescence, softening and growth of microorganisms were inhibited and colour wasmaintained of fresh-cut dragon with modified lotus seed starch coating. Theappearance and quality were improved, therefore the shelf life was extended.