金属-多酚网络/纤维素微纤丝复合物的制备及其抗氧化性和稳定性研究

利用Fe³⁺和单宁酸(TA)制备金属-多酚网络(MPN),并用于纤维素微纤丝(CMF)的功能化改性,以制备CMF-MPN复合物,探讨CMF与MPN制备条件对CMF-MPN复合物抗氧化性和稳定性等的影响。结果表明,MPN可赋予CMF抗氧化性,当TA与Fe³⁺质量比为4∶1、pH值为3制备的MPN添加量为2%(相对于绝干CMF质量)时,所得CMF-MPN复合物的DPPH清除率达97.0%;热重分析结果表明,CMF-MPN复合物残余质量相对于CMF提高了8.13%,但最大热降解温度略有下降;傅里叶变换红外光谱分析结果表明,CMF与MPN间的吸附为物理吸附;以CMF为载体可以提高MPN结构的稳定性,放置60天后仍能保持初始抗氧化性的80%左右,具有缓慢持续释放抗氧化因子的性能,这为开发绿色食品保鲜包装材料提供了新思路。     

蓝莓叶多酚研究进展及其在食品中的应用

多酚是一种植物次生代谢物,包括花色苷类、黄酮类、黄酮醇类、酚酸等成分,其结构多样,具有抗氧化、抗肿瘤、抑菌、预防心血管疾病等多种生物活性。蓝莓,又称越桔,属于杜鹃花科,越橘属植物,常绿或落叶灌木。蓝莓叶全绿或有锯齿,可以药食两用。近年来,蓝莓叶因多酚类物质含量高而倍受关注,蓝莓叶多酚具有多种生理功能逐渐成为天然产物化学研究的热点。本文综述了蓝莓叶多酚的提取技术、分离纯化技术、多酚总量的测定方法、组成分析与结构鉴定、生物活性,开发利用并展望了其发展前景。蓝莓叶多酚是值得研究与开发的天然植物成分。     

葡萄渣多酚的分布、生物活性及其在食品中的 应用研究进展

许多水果在加工过程中会产生大量的副产物,如葡萄酒酿造过程中产生的葡萄果渣(grape pomace,GP),由于其中含有丰富的生物活性物质,如多酚、膳食纤维、有机酸和不饱和脂肪酸等,已成为医药、化妆品和食品工业提取植物活性物质的廉价来源。尤其是酚类化合物受到越来越多的关注,葡萄渣中的酚类化合物是一类次生代谢产物,主要包括类黄酮、花青素和白藜芦醇等,很多研究已经证实这些酚类化合物具有抗氧化、抗菌、抗病毒、抗炎和抗癌等生物活性,因此,如何从葡萄渣中提取多酚化合物并将其开发成功能性食品配料,成为越来越多的企业和学者的关注。在此本文对GP多酚的组成分布、生物活性、在食品中的稳定性及其应用等进行了较全面的总结,旨在为葡萄渣多酚功能性食品的开发提供参考。     

γ-谷氨酰转肽酶的催化特性及其在食品领域应用研究进展

γ-谷氨酰转肽酶广泛存在于生物体中,可以专一性催化γ-谷氨酰基的转移反应,参与生物体内谷胱甘肽代谢和γ-谷氨酰基循环等生理过程。随着食品酶学、合成生物学技术的发展,γ-谷氨酰转肽酶在生物催化领域的应用也日渐受到重视。基于其水解和转肽催化活性,γ-谷氨酰转肽酶可被应用于茶氨酸等多种γ-谷氨酰化合物的生物催化合成。利用酶工程手段进一步优化γ-谷氨酰转肽酶的催化特性,提高目标产物产率,使得γ-谷氨酰转肽酶在食品功能因子的绿色生物制造领域具有较好的应用前景。文章综述了γ-谷氨酰转肽酶的分子结构、催化机制及其在食品工业中的应用现状,并重点关注γ-谷氨酰转肽酶的分子改造及其在催化合成L-茶氨酸领域的应用,以期为γ-谷氨酰转肽酶在食品领域的研究及应用提供参考。     

辣木多酚提取、功能及应用研究进展

辣木是一种药食两用多年生的植物,多酚是其主要活性成分之一。本文综述了辣木不同部位多酚种类和含量、辣木多酚提取方法、辣木多酚功效、辣木多酚应用的发展现状,其中重点综述了辣木多酚抗氧化、抗炎、抗菌、抗病毒、抗癌和降糖等功能的研究现状,期望能为辣木多酚的未来研究和应用提供理论基础以及新的见解。     

多酚/植物蛋白质复合物的界面特性及其在乳液中的应用研究进展

植物蛋白作为天然食品乳化剂,其优势不言而喻.但蛋白质易与食品中的酚类物质结合而影响其乳化特性,并与环境因素有关.已有诸多文献报道了多酚极易与植物蛋白结合形成微粒吸附在油/水界面,但是并无系统论述多酚和植物蛋白形成复合物对稳定乳液的作用方式及对蛋白质结构的影响,进而影响其界面特性.基于此,文章综述了多酚与植物蛋白质的结合...     

植物多酚的抑菌活性及其在食品保鲜中的应用

植物多酚是一种植物次生代谢物, 其结构多样, 具有多种生物活性。植物多酚的抑菌活性是其重要活性之一, 并在食品中得到了广泛的应用。本文主要综述了植物多酚的组成、性质, 抑菌机制以及在食品保鲜中的应用。     

淀粉-多酚复合物制备及其消化特性研究进展

多酚是一种从植物中提取的,具有降血糖、抗炎、抗氧化、抗癌和抗菌特性的化合物。在一定条件下,淀粉可以与多酚发生相互作用,形成两种类型的复合物。一种是非包合物,即酚类化合物的羟基和羰基与淀粉相互作用形成分子间聚集体;另一种是V型包合物,即酚类化合物部分包封在淀粉的内部疏水螺旋内。上述两种复合物均对降低淀粉消化率有积极作用,但受加工方式、淀粉和多酚种类的影响。因此,本文在总结上述因素对淀粉-多酚复合物理化及消化特性影响的基础上,指出目前淀粉-多酚复合物研究中存在的不足之处,提出进一步的研究重点,以期为淀粉-多酚复合物在不同食品中的应用提供参考。     

蛋白质-多酚相互作用及在食品开发中的应用进展

多酚是一种常见的植物化学物质,能有效预防心血管疾病、高血压和肿瘤等病变的出现,却因化学性质不稳定在食品中应用受到限制。蛋白质是重要的食品大分子营养成分,其功能性质对食品营养、品质至关重要。多酚与蛋白质通过共价相互作用和非共价相互作用形成蛋白质-多酚复合物,从而影响蛋白质的功能性质。文章综述了蛋白质-多酚相互作用方式、蛋白质-多酚的乳化特性、凝胶性和抗氧化性以及蛋白质-多酚乳液递送生物活性物质和对食品色泽、风味的影响,以期为蛋白质-多酚功能特性的研究及在食品开发中的应用提供理论依据。     

苹果多酚功能及其作用机理的研究进展

大量研究表明苹果多酚将是重要的食品和药品添加剂,其很多功能性优于其他多酚。苹果多酚的抗氧化、抗癌、降血压、预防心脏病、抗龋齿、抗过敏、抗病毒等功能性已经被人们认可,但部分功能性的作用机理还并不十分明确,有待研究。介绍近年来关于苹果多酚几种重要生理功能的研究进展以及一些功能性作用机理的推断。     

纤维素微纤丝改性方式对胶原纤维复合膜性能的影响

利用金属-多酚网络（metal-polyphenol network,MPN）和不同程度羧基化改性制备的纤维素微纤丝（cellulose microfibrils,CMF）与胶原纤维（collagen fiber,CF）共混制成复合膜,探究CMF改性方式对复合膜性能的影响。结果表明：MPN改性的CMF能使复合膜抗氧化性能提高51.49%,断裂延伸率和阻光性也有显著提高;MPN和高含量羧甲基共同改性的CMF能最大程度降低MPN对复合膜机械强度的影响;MPN和高含量羧乙基共同改性的CMF能使复合膜对水蒸气和氧气的阻隔能力分别提高1.30 倍和3.48 倍。扫描电子显微镜和红外光谱分析表明不同方式改性的CMF与CF之间是物理交联且具有良好的相容性,从而为提高复合膜的性能以更好地应用到食品包装领域提供了一种新手段。     

绝缘竹浆制备过程中酸处理除铁离子规律研究

探讨了竹浆制备过程中,硫酸和柠檬酸处理对铁离子去除的影响,揭示了铁离子的去除规律,建立了相应的预测模型,并对高纯度绝缘竹浆的性能进行分析。结果表明,采用硫酸和柠檬酸处理竹浆,铁离子的去除历程大致可分为快速去除、充分去除和残余去除3个阶段。当酸用量1%、处理时间60 min、处理温度70℃时,铁离子的去除效果较佳。与硫酸处理相比,柠檬酸处理所得纸浆纤维损伤小,聚合度无明显变化,纸张的物理强度较优。经硫酸和柠檬酸处理后的竹浆均可满足高纯度绝缘浆的质量要求。     

Lactic Fermentation of Non-Tannin and High-Tannin Cereals: Effects on In Vitro Estimation of Iron Availability and Phytate Hydrolysis

The effect on iron availability estimated in vitro and phytate hydrolysis was investigated in non-tannin and high-tannin cereals, lactic fermented as flour/water slurries or gruels. A natural starter culture initiated fermentation and addition of germinated flour and phytase in the fermentation process was tested. Lactic fermentation of nontannin cereals with added flour germinated sorghum seeds or wheat phytase increased iron solubility from about 4% up to 9 and 50%, respectively. Soaking flour in water before adding starter culture had a similar effect. The increase in soluble iron was strongly related to enzymatic deeradation of phytate (p<0.001). The reduction of inositol hexa- and pentaphosphates was about 50% with added germinated flour. Reduction was > 90% after soaking the flour prior to fermentation and almost complete with 50 mg phytase added. High-tannin cereals showed a minor increase in soluble iron after fermentation, ascribed to the inhibitory effect of tannins (both on iron solubility and on enzymatic hydrolysis of phytate). Lactic-fermented cereal foods have a potential in developing countries to improve iron nutrition.     

Phytochemical constituents and antioxidant capacity of different pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars

Six pecan cultivars were analyzed for their antioxidant capacity (AC), total phenolics (TP), condensed tannin (CT), HPLC phenolic profile, tocopherol and fatty acid composition. Kernels which included the outer brown testa or pellicle, and shells which is the hard cover that surrounds the kernel, were evaluated for each cultivar. Strong correlations were found in kernels between AC and TP for both DPPH (r² = 0.98) and AC_ORAC (r² = 0.75) antioxidant assays. AC_ORAC values ranged from 372 to 817 μmol trolox equivalents/g defatted kernel, corresponding to Desirable and Kanza cultivars, respectively. CT ranged from 23 to 47 mg catechin equivalents/g defatted kernel and TP from 62 to 106 mg of chlorogenic acid equivalents/g defatted kernel. After a consecutive basic-acid hydrolysis, gallic acid, ellagic acid, catechin and epicatechin were identified by HPLC. The TP, AC and CT were 6, 4.5 and 18 times higher, respectively, for shells compared to kernels. The presence of phenolic compounds with high antioxidant capacity in kernels and shells indicates pecans can be considered an important dietary source of antioxidants.     

可食性蛋白膜在食品包装中的应用研究进展

采用杨梅单宁对酪蛋白膜进行改性,使用溶液浇铸法制备杨梅单宁-酪蛋白复合膜。研究不同比例的杨梅单宁对复合膜水溶性、不透明度、拉伸性能、形貌特征、水蒸气透过率、热稳定性和抗氧化性的影响。研究结果表明,复合膜的水溶性、拉伸性能、水蒸气透过率、热稳定性和抗氧化性得到有效改善。随着杨梅单宁含量的增加,复合膜的透明度下降,当杨梅单宁质量分数达15%时,复合膜的整体改性效果最优,拉伸强度较纯酪蛋白膜提高了近70.9%,水蒸气透过率下降了72.1%,DPPH自由基清除率提高了18.2%。由此可见,杨梅单宁可作为酪蛋白膜的多功能性改性剂,在食品包装领域有潜在应用前景。     

Evidence for the inhibition of the terminal step of ruminal α-linolenic acid biohydrogenation by condensed tannins

Effects of condensed tannins (CT), either via extract or plant-bound, and saponin extract on ruminal biohydrogenation of α-linolenic acid (ALA) were investigated in vitro. Grass-clover hay served as basal diet (control). The control hay was supplemented with extracts contributing either CT from Acacia mearnsii [7.9% of dietary dry matter (DM)] or saponins from Yucca schidigera (1.1% of DM). The fourth treatment consisted of dried sainfoin (Onobrychis viciifolia), a CT-containing forage legume, in an amount also providing 7.9% CT in dietary DM. All diets were supplemented with linseed oil at a level contributing 60% of total dietary ALA in all treatments. Diets were incubated for 10 d (n = 4) in the rumen simulation technique system, using the last 5 d for statistical evaluation. Fatty acids were analyzed in feed, feed residues, incubation fluid, and its effluent. Data were subjected to ANOVA considering diet and experimental run as main effects. Both CT treatments reduced ruminal fiber and crude protein degradation, and lowered incubation fluid ammonia concentration. Only the CT extract suppressed methane formation and shifted microbial populations toward bacteria at cost of protozoa. The saponin extract remained without clear effects on fermentation characteristics except for increased protozoal counts. The extent of ALA biohydrogenation was 20% less with the CT plant, but this probably resulted from reduced organic matter degradability rather than from an inhibition of biohydrogenation. After incubation analysis of incubation fluid effluent and feed residues showed a considerable proportion of the 3 biohydrogenation intermediates, cis-9, trans-11, cis-15 C18:3, trans-11, cis-15 C18:2, and trans-11 C18:1, which did not occur in the initial feeds. Only the CT-extract diet led to a different profile in the effluent compared with the control diet with trans-11 C18:1 being considerably increased at cost of C18:0. This could have been achieved by suppressing protozoa and enhancing the bacterial population, thus removing potential microbes involved in biohydrogenation and increasing competition between bacteria involved in biohydrogenation and others. The elevation of trans-11 C18:1 as the precursor of cis-9, trans-11 conjugated linoleic acid formed in body tissue and mammary gland is probably favorable from a human health point of view.     

Sensory astringency of 5-O-caffeoylquinic acid,tannic acid and grape-seed tannin by a time-intensity procedure

The astringency of 5-0-caffeoylquinic acid (5-CQA) was investigated by a time-intensity technique alongside those of tannic acid and grape-seed tannin. Significant differences were recorded between 5-CQA and the other phenolic solutions for the intensity of the response, its persistence (or overall duration), its fading (or decline from maximum intensity to zero), and for the total gustatory response (or total area under the time-intensity curve). In each case, 5-CQA elicited a weaker response than either grape-seed tannin or tannic acid. Nevertheless, overall, panellists recorded a response for 5-CQA that was qualitatively similar to those for tannic acid and grape-seed tannin, which are traditionally accepted as astringents. This phenomenon occurred, despite 5-CQA having a molecular mass of 354 and containing only one 1,2-dihydroxyphenyl residue, which would place it outwith the traditional definition of an astringent. The requirements appropriate to vegetable tanning may not therefore apply to oral astringency.     

Effect of dietary quebracho tannin extract on milk fatty acid composition in cows

The aim of this study was to examine the capacity of quebracho tannin extract (QTE) to modulate the fatty acid (FA) profile in the milk fat of cows. Fifty Holstein cows yielding 33.2 ± 8.2 kg/d of milk were divided into 2 groups. The cows were fed a basal diet with a forage-concentrate ratio of 66:34 on a dry matter (DM) basis. Diets tested were control (CON, basal diet without QTE) and basal diet plus 15 or 30 g of QTE/kg of DM (QTE₁₅ and QTE₃₀, respectively). Two treatments could be tested simultaneously and were arranged along 6 periods. The milk FA profile was characterized by increments in the proportion of linoleic (LA) and α-linolenic acid (α-LNA) (QTE₁₅ = 10 and 6.1%; QTE₃₀ = 28 and 25%, respectively) compared to CON, which might indicate reduced ruminal biohydrogenation (BH) of both dietary LA and α-LNA. Vaccenic acid (VA) in the milk fat was reduced (QTE₁₅ 8.9% and QTE₃₀ 12%) compared to CON, which may be linked to inhibited BH of LA and α-LNA. Rumenic acid (RA), a conjugated LA (cis-9,trans-11 conjugated linoleic acid) and an important human health promoter, was unfortunately decreased (QTE₁₅ 8.3% and QTE₃₀ 16%) in the milk compared with CON, probably because of inhibited ruminal BH of LA. However, reduced RA in the milk was probably due to reduced availability of VA produced in the rumen and the consequently low VA available to be desaturated to RA in the mammary gland by Δ⁹-desaturase. The proportions of total polyunsaturated FA were increased with QTE₁₅ and QTE₃₀ by 4.7 and 15% compared to CON, respectively, and the long-chain FA proportions were also increased (QTE₁₅ 2.0% and QTE₃₀ 8.2%). Moreover, myristic and palmitic acid were reduced by QTE₃₀ (9.6 and 3.3%, respectively) compared to CON, which also contributed to increasing the nutritional quality of milk because they are recognized to increase high-density lipoprotein in humans. Branched-chain FA in milk was reduced with QTE treatments, which indicates inhibited ruminal BH and microbial activity. In general, our findings suggest that dietary QTE have the potential to modulate FA profile of milk fat, and this effect is dosage dependent. Because QTE influenced the FA profile of milk fat both positively and negatively, further research is needed before concluding that QTE may improve the nutritional quality of cow milk fat in human diets.