黄原胶添加对碱法诱导魔芋胶凝胶特性及凝胶机制的影响

【目的】探究黄原胶添加量对魔芋胶凝胶特性及凝胶机制的影响,为相关凝胶食品的开发利用提供理论依据和技术参考。【方法】以2%的魔芋胶溶胶为基质,通过添加不同浓度的黄原胶,制备混合多糖体系,并在2%的碱浓度（Na₂CO₃）及90℃的高温下加热混合体系2 h,冷却后制得不同黄原胶含量（0-1.5%,w/v）的混合凝胶。通过测定混合凝胶强度,研究去离子水浸泡、2%柠檬酸溶液浸泡和冻融处理对凝胶样品的影响。同时,采用扫描电镜观察不同处理凝胶的微观形貌,探究不同处理及黄原胶添加量对魔芋胶凝胶结构的影响。另外,基于流变学、X-射线衍射以及热重分析等手段,探究魔芋胶-黄原胶混合体系在热碱处理过程中凝胶网络的形成过程,揭示凝胶化机制。【结果】90℃恒温加热2 h后,随黄原胶含量增加,混合凝胶强度反而降低,表明90℃加热过程中,黄原胶的存在影响了魔芋胶凝胶网络的形成。但室温条件下,黄原胶含量越高,混合凝胶强度也越高,表明冷却过程中黄原胶可能加强了凝胶网络。经去离子水、2%柠檬酸溶液浸泡后,各处理凝胶强度均呈下降趋势,以2%柠檬酸溶液浸泡处理后的凝胶强度降低最明显。此外,冻融处理后,魔芋胶凝胶出现明显的析水现象,析水率可达50%,但加入黄原胶后,混合凝胶的析水作用显著降低,黄原胶含量越高,析水作用越弱。流变学测试结果表明,在90℃恒温加热2 h的过程中,随黄原胶添加量增加,体系凝胶化速率减小,表明加入黄原胶降低了魔芋胶凝胶网络的形成。随后对该混合体系进行降温扫描,发现当温度从90℃降低至60℃时,凝胶弹性模量呈明显降低趋势,当温度继续降低至室温时,凝胶弹性模量呈明显增加趋势,转折点所对应的温度为60℃,温度越低,弹性模量越高,表明黄原胶分子在60℃时开始与魔芋胶网络发生协同结合作用。【结论】黄原胶添加可显著提高碱法诱导的魔芋胶凝胶在室温下的凝胶强度,同时可改善该凝胶的冻融稳定性,该结论可为魔芋胶凝胶相关食品的开发提供有益参考。     

Effect of xanthan gum on the degradation of cereal β-glucan by ascorbic acid

Oat and barley β-glucans are polysaccharides known for their beneficial effects on glycemia and cholesterol. These physiological effects seem to be related to increased viscosity in the digestive tract. It has recently been shown that free radicals derived from the reaction of ascorbic acid and oxygen can cause a viscosity loss in β-glucan due to depolymerization through the Fenton reaction. However, recent studies have reported a synergistic effect between xanthan gum and β-glucan on viscosity in heat-treated fruit juices. Therefore, the objective of this study was to determine if xanthan gum has a protective effect against OH radical-induced depolymerization of β-glucan by ascorbic acid. Oat β-glucan (0.4%) solutions were studied in water at pH 4. Ascorbic acid concentrations and viscosity profiles were measured over a period of 56 days. The addition of ascorbic acid caused a rapid decrease in β-glucan viscosity. The presence of xanthan gum reduced the viscosity loss (p ≤ 0.0001) but did not provide complete protection for β-glucan over time. Therefore, incorporation of β-glucan in food formulations still presents a challenge in ensuring its physical and nutritional stability in the final product. The use of OH radical scavengers such as sugars and antioxidant compounds could be used in addition to xanthan gum to obtain improved protection.     

黄原胶降解菌菌株X08a产酶和降解能力的研究

研究了从土壤中用平板划线法分离出的1株黄原胶降解菌,所产酶的酶活、酶学性质、降黏率和氮源磷源对该菌产酶的影响。结果表明:X08a降解黄原胶以NH4Cl和Na2HPO4为氮源和磷源、pH为5~6、在30~40℃的条件下降解效果最好。     

扁桃胶组分和多糖结构的研究

【目的】研究扁桃胶的氨基酸和单糖组成以及多糖结构。【方法】利用离子色谱仪测定扁桃胶的氨基酸和单糖组成;采用红外色谱仪分析多糖结构。【结果】扁桃胶的氨基酸成分为Arg、Ala、Thr、Gly、Val、Ser、Pro、His、Phe、Glu、Asp、Tyr等12种氨基酸。其中Thr含量(百分比)最高,为47.89%。扁桃胶的单糖主要由葡萄糖醛酸、木糖和半乳糖和阿拉伯糖组成。另外,还有少量的鼠李糖和海藻糖,这6种成分的摩尔比为24.35﹕9.25﹕33.75﹕31.60﹕0.74﹕0.31。初步推断扁桃胶的多糖主链结构可能由1,6-linked Galp和1,4-linked Araf构成;非还原性末端基团为1-linked Fucp、1-linked Ribf或1-linked GluA;分枝点主要位于1,2,6-linked Galp上。【结论】本研究可以作为扁桃胶深度开发利用的重要依据。     

不同pH对扁桃胶水解物晶体特性的影响

利用RINT2000 vertical goniometer型X-衍射仪测定不同pH条件下扁桃胶水解物的结晶度,研究不同pH条件对扁桃胶晶体特性的影响规律,并用电子显微镜观察水解物的微晶结构。结果表明:1)pH的改变不仅能够使非晶体的扁桃胶表现出晶体特性,而且对晶相也有极显著的影响,在pH3～1,晶体结构与多糖的微纤维化有关,在pH11～13,晶体与多糖的结构有关;2)以pH7为中心坐标,随着pH的不断降低,扁桃胶的结晶度变化符合方程y=10.94201e-(x-2.23006)2/1.872403(R2=0.85175);随着pH的不断增加,扁桃胶的结晶度变化规律符合方程y=-8.83822+1.38118x(R2=0.89675)。     

松脂中树脂酸的酸异构分离与枞酸分子结构

松脂中枞酸型树脂酸在酸的作用下经过异构反应、结晶分离得到99.15%高纯度(-)-(4R,10R,9S,5R)-7,13-二烯-18-枞酸,得率74.2%.通过MS,1HNMR,13CNMR,IR光谱分析和单晶X-光衍射研究确证其化合物分子结构,其单晶X-光衍射测试数据与湿地松松香和马尾松松香直接经过重结晶分离得到枞酸样品的结果一致,都为单斜晶系,P21空间群,分子绝对构型和天然枞酸构型一样.在枞酸晶体结构中2个枞酸分子的羧基生成氢键连接是得到高纯度结晶的主要原因.     

微波诱变筛选无色素黄原胶产生菌

[目的]筛选出含色素较少或无色素的黄原胶生成菌株,生产高品质的透明黄原胶,促进黄原胶发酵工业的发展。[方法]经过各个平板内比较、各个稀释度内比较、各个试验组内比较及各种条件试验内的单菌落颜色比较,选取出发菌株。对出发菌株进行微波照射诱变,并选取最佳照射条件。[结果]在微波强度为60%的条件下照射40s,每隔10s进行冷却为最佳的黄单胞菌微波诱变条件。经显微镜检测、连续传代后的菌落形态观察及所产黄原胶的比较结果表明,该试验使用微波诱变筛选已获得1株产生无色素黄原胶的黄单胞菌caM45-5突变株,该突变株可用于生产高品质的透明黄原胶。[结论]为生产高品质的透明黄原胶、减少黄原胶提取工艺过程提供了方便。     

结冷胶发酵生产工艺优化研究

通过摇瓶试验,得出了结冷胶生产工艺中的最佳发酵培养基配方。通过改变发酵培养基中碳源、氮源的百分比,进而测量结冷胶发酵液的粘度、产胶率,来确定最佳发酵工艺。50 L罐发酵试验得到发酵液粘度为19 600 cp,粗胶产率达1.73%,清胶产率0.80%,试验结果为生产中优化结冷胶的发酵工艺、提高结冷胶的粘度和产胶率提供科学依据。     

Effects of Bicarbonate,Xanthan Gum,and Preparation Methods on Biochemical,Physicochemical, and Gel Properties of Nile Tilapia (Oreochomis niloticus Linn) Mince

This study was aimed to determine the effects of phosphate compound substitutions (sodium bicarbonate and xanthan gum) and preparation methods—headed, gutted whole fish, and mince; fresh and after frozen storage (?20°C for 3 months)—on Nile tilapia mince qualities. Results showed that bicarbonate (0.3% with 8% sucrose/sorbitol) is an efficient phosphate compound replacement as evidenced by the comparative values of salt extractable protein, Ca²⁺-ATPase activity, total sulfhydryl content, and textural properties to those of the phosphate-added—0.3% sodium tripolyphosphate (STPP) with 8% sucrose-sorbitol—sample after 3-month frozen storage (p > 0.05). Both cryoprotected samples containing STPP or bicarbonate exhibited higher denaturation temperatures of myosin than others. Xanthan gum (0.5%) could neither stabilize the biochemical and physicochemical properties of mince during 3-month frozen storage nor improve textural properties of gel from frozen whole fish.     

沙枣树采胶不同创口类型下的出胶量

本文对沙枣树的出胶,进行了不同创口类型和创口数量与出胶量关系的试验。结果表明:在成龄树的主干上或者老树的树瘤上进行人为创伤制造创口的办法,都可获得较多的出胶量,并且出胶量随创口数的增加而增加。