【作者】 张美霞；

【导师】 阚建全；

【作者基本信息】 西南大学 ， 农产品加工及贮藏工程， 2009， 博士

【摘要】 莲藕(Nelumbo nucifera Gaertn),含有丰富的淀粉、蛋白质、维生素、铁、钙、生物碱等多种对人体健康有益的物质,具有较高的食用和药用价值,是一种用途十分广泛的水生经济作物。但莲藕采收后易出现褐变,本研究希望找出比较有效的无硫抑制剂控制莲藕的酶促褐变过程,并结合干燥脱水技术和超微粉碎技术,将莲藕加工成超微全藕粉,既有利于莲藕的贮藏和运输,又最大限度的保存了莲藕的各种营养成分。不同粒度的超微全藕粉功能特性的研究,有利于理解超微全藕粉在加工、储存以及使用过程中的质构特征,为解决全藕粉深加工产品的糊化和老化等问题提供理论基础,并为全藕粉产品的品质控制和加工工艺提供参考,指导其在食品工业中的应用。实验研究结果如下:(1)鲜切藕片护色技术研究鲜切藕片的最佳护色剂组合为:柠檬酸0.15%,抗坏血酸0.15%,d1-苹果酸0.25%,L-半胱氨酸0.15%,在加工过程中结合热烫(60℃)可共同抑制酶促褐变的发生。(2)鲜切藕片干燥脱水技术研究应用热风干燥、微波干燥、先微波后热风、以及真空冷冻干燥四种常用的干燥方法对鲜切藕片进行脱水干燥试验,采用干燥速率、碘蓝值、白度和复水性四个指标综合评定干燥后的产品质量,最终确定了热风干燥法是鲜切藕片的最佳干燥方法,并通过正交试验确定了薄层热风干燥的最佳条件为:热风温度70℃、风速0.3m/s、装样量40g。在此条件下,薄层热风干燥数学模型符合单项扩散模型:MR＝0.857412114exp(-0.050102613t)(R~2＝0.96537):通过该模型得到的预测值和真实测定值的比较,表明该方程能够较好的模拟该条件下鲜切藕片的干燥过程。(3)藕淀粉与超微全藕粉的制备技术通过试验研究,确定了藕淀粉采用传统水提法制备,超微全藕粉首先由热风干燥的藕片经粗粉碎后,再通过翻转式振动碾磨混炼机,进行超微粉碎,再用不同目筛筛分而制得。1号样品藕淀粉与超微全藕粉1-淀粉,1-100、1-200、1-300的得率分别为3.23%、34.3%、47.0%、15.3%;2号样品藕淀粉与超微全藕粉2—淀粉、2—100、2—200、2—300的得率分别为3.71%、30.2%、47.6%、19.4%;3号样品藕淀粉与超微全藕粉3—淀粉、3—100、3—200、3—300的得率分别为2.64%、35.3%、38.7%、和22.1%。(4)藕淀粉与超微全藕粉颗粒结构特性的研究藕淀粉颗粒表面光滑,无裂纹,少量破损;大多数颗粒呈棒状,颗粒大小在40μm左右,少部分淀粉颗粒呈椭圆形或圆形,颗粒大小在10—25μm左右,极少数为多角形,有偏心环纹;藕淀粉颗粒偏光十字明显,颗粒较大的棒状淀粉,脐点位于淀粉颗粒的一端,其十字不规则,大部分呈“X”形;颗粒较小的椭圆形或圆形淀粉,脐点位于淀粉颗粒中央,呈垂直十字形或斜十字形,部分呈“X”形;全藕粉经过超微粉碎后,藕淀粉原有的颗粒结构大多被破坏,只能观察到极少完整的淀粉颗粒,且破损的淀粉颗粒与其他的颗粒黏附在一起,形成小的粒子团;超微全藕粉,只能看到部分未被破坏的藕淀粉颗粒的偏光十字;藕淀粉颗粒的结晶结构为B型;超微粉碎后全藕粉呈现A型结晶结构;超微全藕粉随着粒度的减小,衍射峰强度降低,半峰宽增加,结晶区域减小,而非结晶区域增大;1号样品1-淀粉、1-100、1-200、1-300的结晶度分别为:35.77%、25.61%、23.77%、21.81%;2号样品2-淀粉、2-100、2-200、2-300的结晶度分别为:32.30%、28.72%、24.28%、22.49%;3号样品3-淀粉、3-100、3-200、3-300的结晶度分别为:32.96%、28.94%、26.48%、25.76%。1号样品1-淀粉、1-100、1-200、1-300的粒度80%分别分布在19.652μm-73.045μm、8.473μm-135.541μm、8.7μm-88.907μm和7.395μm-56.966μm之间;2号样品2-淀粉、2-100、2-200、2-300的粒度80%分别分布在18.74μm-66.371μ、14.07μm-213.55、7.895μm-63.463μ和7.433μm-53.244之间;3号样品3-淀粉、3-100、3-200、3-300的粒度80%分别分布在17.616μm-76.813、9.979μm-202.63、7.196μm-56.888μm和7.444μm-53.697μm之间。2号淀粉颗粒相对较小,1号淀粉和3号淀粉粒径相近。超微全藕粉100目样品粒径远大于淀粉粒径,200目和300目的样品粒径小于淀粉颗粒。(5)藕淀粉与超微全藕粉糊化特性的研究不同粒度的超微全藕粉,在不同条件下黏度变化趋势与相同品种的藕淀粉相似。但是由于全藕粉中复杂成分之间的相互作用,超微全藕粉的糊化温度高于藕淀粉,另外由于超微粉碎过程已经破坏了淀粉的颗粒结构,所以超微全藕粉糊化所需要的能量低于颗粒完整的藕淀粉;超微全藕粉的溶解度远远高于相应的藕淀粉;不同粒度超微全藕粉的溶解度顺序为为300目＞200目＞100目;超微全藕粉的膨胀度高于淀粉,不同粒度超微全藕粉的膨胀度顺序为100目＞200目＞300目;淀粉的冻融稳定性远远高于超微全藕粉,不同粒度的超微全藕粉的冻融稳定性顺序为100目＞200目＞300目。超微全藕粉的粘度低于藕淀粉,但其稳定性好于藕淀粉;不同粒度的全藕粉中粘度的热稳定性和冷稳定性都表现为100目＜200目和300目,200目和300目之间的稳定性差异不明显。藕淀粉在较低浓度6%时即可形成较好的凝胶,超微全藕粉则要在较高浓度11%时才能形成凝胶,且凝胶强度低,但超微全藕粉形成的凝胶弹性较好。(6)藕淀粉与超微全藕粉糊老化特性的研究超微全藕粉与藕淀粉糊在放置过程中透光率降低,超微全藕粉糊透光率低于藕淀粉;与藕淀粉糊相比超微全藕粉糊更容易沉降,不同粒度超微全藕粉糊的沉降速度大小为300目＞200目＞100目;超微全藕粉与藕淀粉糊或凝胶在存放过程中,碘蓝值和α-淀粉酶酶解率都降低,说明在糊或凝胶中游离淀粉含量降低,淀粉老化在缓慢的进行,同时在存放过程中,超微全藕粉与藕淀粉凝胶的凝胶强度增加,凝胶弹性降低。本论文的创新之处在于:(1)对鲜切藕片进行了四种脱水干燥工艺的研究,优化了热风薄层干燥工艺参数,建立了干燥数学模型,并研究了超微全藕粉的生产工艺,获得了不同品种、不同粒度的超微全藕粉产品。(2)在国内首次系统的研究了不同品种藕淀粉与超微全藕粉的理化性质、颗粒结构和功能性质,为其在食品工业中的应用提供理论依据。本论文鲜切藕片护色部分、热风薄层干燥部分以及藕淀粉与超微全藕粉颗粒结构特性研究部分已分别在《食品工业科技》和《食品科学》上发表。更多还原

【Abstract】 Nelumbo nucifera Gaertn is a kind of hydrophilous economy-crop which can provide ample nutrition such as starch,vitamin,Fe,Ca and alkaloid et al.But after harvested lotus root tends to get browning. Many inhibitors and drying methods were studied to protect fresh-cut lotus root from browning during experiments.The production of super-fine whole-lotus-root powder can keep much of the nutrition and be benefit to the store and conveyance of the lotus root.The study of super-fine whole-lotus-root powder’s functional characteristic provided the theoretic base for structure,pasting and retrogradation characteristics, and the results can be the guidance for application of super-fine whole-lotus powder in food industry.The results as following:(1) The study of protecting fresh-cut lotus root from browningThe best inhibitor combination is:citric acid 0.15%,vc 0.15%,dl-malicacid 0.25%and L-cysteine 0.15%,combined with 60℃water dipping during the production to control browning.(2) The study of drying methods on fresh-cut lotus rootThe fresh-cut lotus root are drying with hot-air drying,microwave drying,microwave+hot-air drying and vacuum freezing drying.The qualities of products are evaluated comprehensively by drying rate, starch-iodine-blue,TW and the ability of water retention.The results show that hot-air drying is the best method to preserve the quality of lotus root.And the best technological drying condition is 70℃,the speed of wind is 0.3m/s and the quantity is 40g.Under this condition,the mathematical drying model equation MR＝0.857412114exp(-0.050102613t)(R~2＝0.96537) has been established.The results show that there is little difference between the speculated results and the calculated outcomes,so the mathematical model equation established on these date can be applied to describe the process of hot-air thin layer drying for fresh-cut lotus roots. (3) The preparation of lotus root starch and super-fine whole-lotus root powderWe get the lotus root starch with the method of extracting with water.The drying slices of lotus root are crushed to get the meal and then transferred to the super micron-milling equipment to gain the finer powder.And the powder is separated to three grades according to their size.The output of each sample is that the percent of 1-starch,1-100,1-200,1-300 is 3.23%,34.3%,47.0%,15.3%each;the percent of 2-starch, 2-100,2-200,2-300 is 3.71%,30.2%,47.6%,19.4%each;the percent of 3-starch,3-100,3-200,3-300 is 2.64%,35.3%,38.7%,and 22.1%each.(4)The study on the structure of lotus root starch and super-fine whole-lotus root powderThe shape and the structure of lotus starch and different sizes of super-fine whole-lotus powder are studied with optical microscope,scanning electron microscope,polarizing microscope and X-ray diffraction.The results show that most of the lotus starch particles are club-shaped and the size are about 40μm and a few of them are elliptic or circular and the size are about 10-25μm,and all of them present apparent ring and their center is on the end of particle.The intrinsic structure of lotus root starch is almost destroyed during super-fine smashing.Little intact starch can be observed,the damaged starch attached to other fragments to form small groups.Otherwise the size of whole-lotus root powder is getting smaller after super-fine smashing,even smaller then starch.The polarization cross is clear and the club-shaped starch shapes“X”,but elliptic and circular starch shape vertical or declining cross and some of them are in the shape of“X”,Most lotus starch structure of super-fine whole-lotus powder is destroyed,only a few“X”or fragmentary“X”and cross can be seen.Lotus starch exhibits a B-type in X-ray diffraction pattern,but after super-fine smashing which exhibits an A-type in X-ray diffraction.With the sizes of the super-fine whole-lotus powder getting smaller,the intention of diffraction apex falls and the extent of crystal minishes and the extent of non-crystal spreads.The crystal degree of each sample is that the percent of 1-starch,1-100,1-200,1-300 is 35.77%,25.61%,23.77%,21.81%each,the percent of 2-starch, 2-100,2-200,2-300 is 32.30%,28.72%,24.28%,22.49%each,the percent of 3-starch,3-100,3-200,3-300 is 32.96%,28.94%,26.48%,25.76%each.The 80%of the size distribution of each sample is that 1-starch, 1-100,1-200,1-300,2-starch,2-100,2-200,2-300,3-starch,3-100,3-200,3-300 is among 19.652μm-73.045μm,8.473μm-135.541μm,8.7μm-88.907μm,7.395μm-56.966μm,18.74μm-66.371μm, 14.07μm-213.55μm,7.895μm- 63.463μm,7.433μm-53.244μm,17.616μm-76.813μm,9.979μm-202.63μm, 7.196μm-56.888μm,7.444μm-53.697μm each.(5) The study of paste characteristic of lotus root starch and super-fine whole-lotus root powderThe results show that the changing direction of viscosity of different size of whole-lotus root powder is similar to the same sort of lotus root starch under varied conditions.The gelatinization temperature of super-fine whole-lotus powder is higher than the lotus root starch due to the complicated component and the reciprocity of each other.The energy needed to gelatinize of super-fine whole-lotus powder is fewer than the lotus root starch because that the structure of starch in whole-lotus powder has been destroyed during super-fine smashing.The super-fine powder is more soluble than the starch.The solubility of different size of super-fine powder is that 300 mesh＞200 mesh＞100 mesh.The swelling power of super-fine powder is better than starch.The swelling power of different size of super-fine whole-lotus powder is that 100 mesh＞200 mesh＞300 mesh.The freezing-thawed stability of lotus starch is much better than super-fine powder.The freezing-thawed stability of different size of super-fine whole-lotus powder is that 100 mesh＞200 mesh＞300 mesh.The viscosity of super-fine whole-lotus root powder is lower than lotus root starch while its stability is better than the starch.The viscosity stability of different size super-fine whole-lotus root powder under high temperature and low temperature are both 100mesh＜200mesh and 300mesh,there is little difference between 200 mesh and 300 mesh.Lotus root starch can gel when the concentration is above 6%while the super-fine whole-lotus root powder can gel only when the concentration is above 11%.The intensity of starch gel is higher than super-fine whole-lotus root powder while the springness is on the contrary.(6) The study of retrogradation of lotus root starch and super-fine whole-lotus root powderThe results show that the paste’s euphotic ratio of lotus root starch and super-fine whole-lotus root powder fall during placement.And the paste’s euphotic ratio of super-fine whole-lotus root powder is lower than that’ of lotus root starch.Comparing with lotus root starch,the super-fine whole-lotus root powder paste more easily incline to delaminate,and the sedimentation rate is getting faster with the size getting smaller.Both the starch-iodine-blue and the decomposeing percent of paste and gel of lotus root starch and the super-fine whole-lotus root powder decline during the placement.The explanation is that the content of dissociated starch are getting fewer during the placement in the paste and gel and the retrogradation is processing slowly.The gel’s intensity is getting stronger and it’s springiness gets lower during placement.The innovations of this paper as following:(1) Four drying methords have been applied for fresh-cut lotus root,and the parameters of hot-air drying are optimized.We work over the producing technics about super-fine whole-lotus root powder and gain the production.(2) The physical and chemical characteristics,granule structure and functional characteristics of lotus root starch and super-fine whole-lotus root powder are studied systemicly for the first time at home.And the research affords the academic foundation for their application in the food insustry.更多还原