【作者】 张帆；

【导师】 郑宝东； 张宁宁；

【作者基本信息】 福建农林大学 ， 食品科学， 2012， 硕士

【摘要】 莲子淀粉是高直链淀粉含量的特异性淀粉，含量达40%以上，具有潜在的开发研究价值。干热法是一种物理改性淀粉的新方法，淀粉的物理化学特性在少量离子胶存在的条件下通过干热处理可以被改善，前期研究表明，添加海藻酸钠干热处理莲子淀粉可以提高其成膜特性。本文对添加海藻酸钠的莲子淀粉进行干热变性处理，研究干热变性莲子淀粉的制备工艺及特性，并进一步确定干热变性莲子淀粉的最佳成膜工艺，在此基础上，进行干热变性莲子淀粉膜的抑菌试验，并将其应用于鲜切火龙果保鲜中。研究成果将为干热变性淀粉的工业化生产提供一定的科学指导，同时也进一步拓展干热变性莲子淀粉的应用途径，为可食性淀粉膜在鲜切水果保鲜中的应用提供一定的理论依据。1.通过研究不同离子胶用量、反应pH、干热处理的温度和时间对干热变性莲子淀粉成膜特性的影响，确定干热变性莲子淀粉的制备工艺参数。结果表明，添加海藻酸钠对莲子淀粉进行干热变性处理能改善莲子淀粉的成膜特性，pH和干热温度对干热变性莲子淀粉的成膜性影响最显著。经正交试验优化，当海藻酸钠质量分数为1.0%、pH7、130℃条件下干热反应3h时制备的干热变性莲子淀粉特性最优，为海藻酸钠与莲子淀粉干热反应的最佳工艺参数。2.以莲子淀粉的颗粒特性、淀粉糊的特性和成膜特性为指标，对莲子淀粉直接干热变性前后以及添加海藻酸钠并结合干热处理制成的海藻酸钠干热变性莲子淀粉的特性进行了系统的研究。结果表明，直接对莲子淀粉干热变性对其特性影响不显著，而添加海藻酸钠对莲子淀粉干热处理后，淀粉颗粒多数呈椭圆形，少部分淀粉颗粒表面有细微裂纹，颗粒彼此粘连，淀粉颗粒表面有粘连物；溶解度升高，膨胀度降低，淀粉糊透明度降低。干热变性处理对提高莲子淀粉糊冻融稳定性的作用不明显；但可以提高莲子淀粉膜的机械性能和阻水性，降低膜的溶解度。布拉班德黏度曲线显示，添加海藻酸钠进行干热变性后莲子淀粉起糊温度和终值黏度降低，热稳定性降低，冷稳定性增强，凝沉性减弱。3.以干热变性莲子淀粉为主要原料，研究变性淀粉用量、甘油用量和干燥温度对干热变性莲子淀粉成膜特性的影响，并采用响应面分析法优化制膜工艺。结果表明，当膜液中干热变性莲子淀粉质量分数为3.5%左右时，淀粉膜性能相对较优；当甘油含量较少时，所形成的膜薄且较干，柔软性差，较易断裂；当甘油含量超过一定量时，膜的力学性能降低，亲水性增强，溶解度增大，且甘油含量越高，膜越易返潮；当甘油用量为1.5%时，各指标均达到最高。适中的干燥温度有助于形成性能良好的淀粉膜，干燥温度较高或较低，形成的淀粉膜的性能均不理想。经综合优化，得到干热变性莲子淀粉的最佳成膜工艺条件为：变性莲子淀粉质量分数为3.53%，甘油质量分数为1.51%，干燥温度80.61℃。4.研究了不同抑菌剂浓度和pH对干热变性莲子淀粉膜抑菌特性的影响，获得最佳抑菌条件，并将其应用于鲜切火龙果的保鲜，结果表明，干热变性莲子淀粉膜液中加入0.015%Nisin和0.06%Natamytin，pH为6，对供试的金黄色葡萄球菌、枯草芽孢杆菌等细菌及黑曲霉、青霉等霉菌均有明显的抑制作用。保鲜试验结果显示，干热变性莲子淀粉涂膜处理可以有效降低鲜切火龙果贮藏期间的水分散失和营养物质损失，延缓衰老和组织软化，有效保持果肉原有色泽，抑制微生物的生长繁殖，改善产品的外观和品质，延长货架期。更多还原

【Abstract】 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.更多还原