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。     

XCCNAU-92生产黄原胶的发酵培养基配方的研究

用Ｌ２７（３１３）正交试验研究ＸＣＣＮＡＵ－９２生产黄原胶的发酵培养基配方。结果表明,碳源和氮源显著影响黄原胶发酵液的粘度,二者的交互作用对黄原胶产量及发酵液粘度的影响皆显著;黄原胶生产的最佳发酵培养基配方（ｇ／Ｌ）为：玉米淀粉６０．０,氮源Ｘ１．０,ＣａＣＯ３３．０,ＭｇＳＯ４·７Ｈ２Ｏ０．５,Ｋ２ＨＰＯ４·３Ｈ２Ｏ１．０（０．０）。３０℃,１５０ｒｐｍ条件下发酵７２ｈ,工业级黄原胶产量达４０．８４ｇ／ｋｇ,发酵液粘度８６０００ｃｐ,丙酮酸含量４．１％,碳源转化率达６８．１％。     

桃胶枸杞新型营养果冻的研制

[目的]调配研制出适合高血脂人群食用的桃胶枸杞新型营养果冻。[方法]以桃胶和枸杞为主要原料,采用单因素和正交试验优化制作桃胶枸杞营养果冻的最佳配方条件。[结果]试验得出,对果冻口感影响最大的是吉利丁粉的添加量,其次是柠檬酸钠的添加量,混合汁的添加量和白砂糖的添加量影响较小。在试验范围内,最佳配方为吉利丁粉4%,混合汁(桃胶汁∶枸杞汁=1∶2)30%,白砂糖3%,柠檬酸钠0.15%。[结论]研制出的桃胶枸杞果冻颜色橙红,风味独特,营养丰富,可给高血脂人群提供更多饮食选择,市场前景广阔。     

蜂胶与杨树胶中八种黄酮与肉桂酸含量的测定

目的:建立区分蜂胶与杨树胶的一种方法。方法:采用高效液相色谱法分析测定不同蜂胶样品中八种黄酮和肉桂酸为考察指标,进行含量比较。结论:真假蜂胶中肉桂酸含量存在一些差异。     

Impact of guar and xanthan gums on proofing and calorimetric parameters of frozen bread dough

The influence of guar and xanthan gum and their combined use on dough proofing rate and its calorimetric properties was investigated. Fusion enthalpy, which is related to the amount of frozen water, was influenced by frozen dough formulation and storage time; specifically gum addition reduced the fusion enthalpy in comparison to control formulation, 76.9 J/g for formulation with both gums and 81.2 J/g for control, at 28th day. Other calorimetric parameters, such as T_g and freezable water amount, were also influenced by frozen storage time. For all formulations, proofing rate of dough after freezing, frozen storage time and thawing, decreased in comparison to non-frozen dough, indicating that the freezing process itself was more detrimental to the proofing rate than storage time. For all formulations, the mean value of proofing rate was 2.97 ± 0.24 cm³ min⁻¹ per 100 g of non-frozen dough and 2.22 ± 0.12 cm³ min⁻¹ per 100 g of frozen dough. Also the proofing rate of non-frozen dough with xanthan gum decreased significantly in relation to dough without gums and dough with only guar gum. Optical microscopy analyses showed that the gas cell production after frozen storage period was reduced, which is in agreement with the proofing rate results.     

昆虫病原线虫Steinernema carpocapsae A11品系叶面应用辅助剂的筛选

研究了12种物质对昆虫病原线虫Steinernema carpocapsae A11品系的抗干燥保护作用。这些物质在试验浓度下对线虫和小菜蛾3龄幼虫的存活以及对线虫的侵染率都无显著影响。线虫加入抗干燥剂后经滤纸干燥法处理和叶面喷洒试验结果都表明,甘油和黄原胶的抗干燥保护作用最好。     

Electrokinetic properties of variable charge clays in the presence of an anionic xanthan polysaccharide and inorganic electrolytes

The effect of the electrolytes (MA: NaCl, MgCl₂ , PbCl₂ , and NaH₂PO₄ ) on the polymeric (a) weak-stabilization (PWST), (b) flocculation (PFL); and (c) stabilization (PST) of allophane in the presence of xanthan polysaccharide (GX), was investigated by electrophoretic mobility (EPM) measurements. At pH 6.5 (i.e.p.), with further addition of chlorides, the decrease in the absolute value of the negative EPM (|—EPM|) of allophane in 0.01 mm MA solutions indicated the suppression of PWST and PST, respectively, probably due to the decrease in the repulsive force originating from the negatively charged GX-chains with the addition of MA. By first addition of MA, the decrease in the |—EPM| value of allophane in 0.01 mm NaCl and MgCl₂ solutions also showed the suppression of PWST and PST. In 0.01 mm PbCl₂ and NaH₂PO. solutions, the increase in the EPM and |—EPM| values of allophane reflected the dispersion due to the specific adsorption of Pb₂₊ and H₂PO₄ - ions on the negatively and positively charged sites of the surface, respectively. At pH 4.5, the decrease in the |—EPM| value of allophane in 0.1 mm NaH₂PO₄ solution indicated the suppression of PST due to the specific adsorption of H₂PO₄ - ion on the positively charged surface of the particles. The absence of (i) PWST in the presence of GX and (ii) high stability in the presence of cationic lead species for the flocculated imogolite at pH 8.5 can be attributed to the tubular structure proposed by Cradwick et al. (1972: Nature (London) Phys. Sci., 240, 187-189), namely, to the difficulty in the development of a negative charge on the outer surface of its unit particle.     

Effect of particle size of halloysite on the deflocculation of mutual flocs of allophane and halloysite at pH 6.5 in dilute xanthan polysaccharide solutions

The effect of the particle size of halloysite on the deflocculation of mutual floes of allophane and halloysite in the presence of anionic xanthan polysaccharide was investigated spectrophotometrically. Although allophane which flocculated at the i.e.p. (pH 6.5) exhibited polymeric (i) weak-stabilization (PWST), (li) flocculation (PFL), and (iii) stabilization (PST) with increasing addition of xanthan, allophane and halloysite which flocculated mutually at pH 6.5 inhibited the deflocculation, viz., PWST and PST. Halloysite with a smaller average particle size (i.e., 0.08,um in average diameter) than the suspended microaggregates (SMAs) of allophane inhibited significantly the deflocculation, suggesting that the halloysite particles flocculated around the allophane particles. Halloysite with a larger average particle size (i.e., 0.2 μn in average diameter) than the SMAs of allophane slightly inhibited the deflocculation, suggesting that the halloysite particles were attached to the center of the flocculated SMAs of allophane. The inhibitory effects of particle arrangements on the deflocculation of the mutual floes of allophane-montmorillonite and allophanekaolinite were also investigated comparatively.     

Healed long-bone fractures in wild birds

AIM: To build a profi le of the oral lesions that occur in sheep in New Zealand that need to be considered within the differential diagnosis of foot-and-mouth disease.

METHODS: Lesions of the anterior lips and gums of sheep were surveyed in two abattoirs, photographed, and described grossly and histopathologically.

RESULTS: A sequence of lesions in order of age and stage of healing are described and illustrated, and their pathogenesis discussed. Lesions of the midline of the lips and gums of traumatic or irritant aetiology were common, and the prevalence was higher in adult sheep than in lambs.

CONCLUSIONS: The majority of lesions observed appeared to be primarily of traumatic aetiology. They probably arose from the fright/flight response behaviour of sheep, resulting in the mouth impacting against wire fences or yard railings while being handled. A smaller percentage of lesions may have been due to abrasive or irritant feed or soil. The presence of plant material and bacteria in lesions delayed healing and contributed to the formation of ulcers.     

Correlating the fineness and residual gum content of degummed hemp fibres

It is well known residual gum exists in degummed or retted hemp fibres. Gum removal results in improvement in fibre fineness and the properties of the resultant hemp yarns. However, it is not known what correlation if any exists between the residual gum content in retted hemp fibres and the fibre fineness, described in terms of fibre width in this paper. This study examined the mean width and coefficient of variation (CV) of fibre width of seventeen chemically retted hemp samples with reference to residual gum content. The mean and CV of fibre width were obtained from an Optical fibre diameter analyser (OFDA 100). The linear regression analysis results show that the mean fibre width is directly proportional to the residual gum content. A slightly weaker linear correlation also exists between the coefficient of variation of fibre width and the residual gum content. The strong linear co-relation between the mean of fibre width and the residual gum content is a significant outcome, since testing for fibre width using the OFDA is a much simpler and quicker process than testing the residual gum content. Scanning Electron Microscopy (SEM) reinforces the OFDA findings. SEM micrographs show a flat ribbon like fibre cross-section hence the term “fibre width” is used instead of fibre diameter. Spectral differences in the untreated dry decorticated skin samples and chemically treated and subsequently carded samples indicate delignification. The peaks at 1370 cm⁻¹, 1325 cm⁻¹, 1733 cm⁻¹, and 1600 cm⁻¹ attributed to lignin in the untreated samples are missing from the spectra of the treated samples. The spectra of the treated samples are more amine-dominated with some of the OH character lost.