新型植物基载体对乳糖酶的高效递送及保护

为解决口服酶制剂易被胃液的强酸环境破坏其效价,影响乳糖不耐受症治疗效果的问题,制备一种可以保护乳糖酶过胃而不失去活性的新型植物基载体。采用新型植物基材料向日葵孢粉素外壁胶囊为载体,用于乳糖酶的负载及保护。通过负载、包膜、释放等实验以及采用扫描电子显微镜、激光共聚焦显微镜等表征手段,确定5%海藻酸钠与6%羧甲基茯苓多糖在体积比为1∶1混合所得的凝胶球体外释放效果最佳,实现在消化道中的响应性释放。进一步实验发现,经冻干处理后该体系也具备成为乳糖酶冻干保护剂的潜力。基于此,实验成功论证了向日葵孢粉素外壁胶囊递送体系可以作为乳糖酶的高效递送及保护载体的可行性,为乳糖不耐受症的治疗提供了新的思路。     

Impact of whey protein isolates and concentrates on the formation of protein nanoparticles‐stabilised Pickering emulsions

Whey protein nanoparticles (NPs) were prepared by heat‐induced method. The influences of whey protein isolates (WPIs) and concentrates (WPCs) on the formation of NPs were first investigated. Then Pickering emulsions were produced by protein NPs and their properties were evaluated. After heat treatment, WPC NPs showed larger particle size, higher stability against NaCl, lower negative charge and contact angle between air and water. Dispersions of WPC NPs appeared as higher turbidity and viscosity than those of WPI NPs. The interfacial tension of WPC NPs (~7.9 mN/m at 3 wt% NPs) was greatly lower than that of WPI NPs (~12.1 mN/m at 3 wt% NPs). WPC NPs‐stabilised emulsions had smaller particle size and were more homogeneous than WPI NPs‐stabilised emulsions. WPC NPs‐stabilised emulsions had higher stability against NaCl, pH and coalescence during storage.     

Hydrocolloids with emulsifying capacity. Part 2 – Adsorption properties at the n-hexadecane–Water interface

The ability to adsorb at n-hexadecane – water interface of natural hydrocolloids was quantified by dynamic drop tensiometry. Conventional and matured hydrocolloids samples from Acacia senegal, Acacia seyal (AcSey), Sugar Beet Pectin (SBP) and natural untreated Gum Ghatti (GG), were studied in aqueous solutions at pH 4.5. Maturation of A. senegal gum (Acacia (sen) SUPERGUM? EM2, designated as EM2) increased its ability to lower interfacial tension and the elastic characteristics of the interfacial film. This change in properties can be attributed to the increase in molecular weight and in arabino-galactan-protein (AGP) content. EM2 exhibited the best interfacial properties. Conventional and matured AcSey presented interfacial properties that were similar to conventional A. senegal (GAc), correlating with minimal changes observed in their structural features after maturation. Gum ghatti reacted similarly to EM2 and presented relatively fast kinetic profiles, revealing the good qualities of this gum. The kinetics associated with all the hydrocolloids at pH 4.5 have been described using a mathematical model, from which quantitative parameters as onset time or half-time of interfacial-tension-decrease were determined. Compared to the other hydrocolloids, SBP adsorbs by a different mechanism. However, pectin presented the lowest final interfacial tension and gave the more elastic interfacial film. Acidification of hydrocolloid solutions to pH 3.1 increased both the ability to lower the interfacial tension and the elastic characteristics of interfacial film. The effect of structural modifications on interfacial properties was demonstrated, and clarifies further the already observed emulsification behaviour of the studied hydrocolloid.     

Effect of freezing and frozen storage on the gelatinization and retrogradation of amylopectin in dough baked in a differential scanning calorimeter

Frozen and non-frozen dough were baked in a differential scanning calorimeter (DSC) pan (heated in the calorimeter at temperatures similar to those of the center of the crumb during baking) and were aged at different temperatures. Gelatinized dough (DSC-baked dough) was heated again in the DSC. This methodology permitted us to study the effects of dough freezing and frozen storage on gelatinization and retrogradation of starch. During storage of frozen doughs at −18 °C an increase in the gelatinization enthalpy after 150 day of storage was observed. At 230 days of frozen storage a decrease in the onset temperature and an increase in the gelatinization temperature range was also detected. An increase of starch retrogradation with time of storage in frozen conditions was observed. During the aging of dough baked in DSC, a higher retrogradation temperature range was detected together with a faster retrogradation of starch at low temperature of aging.     

Innovative applications of high-intensity ultrasound in the development of functional food ingredients: Production of protein hydrolysates and bioactive peptides

In recent years, the research on functional peptide generation for the development of functional foods has focused, among other issues, on the enhancement of enzymatic hydrolysis by means of high-intensity ultrasound (HIU) application. It has been suggested that the use of HIU in pretreatment and during the hydrolysis process can modify protein conformation by affecting hydrogen bonds and hydrophobic interactions, disrupting the quaternary and/or tertiary structure of proteins due to the effects of cavitation. Therefore, these structural modifications may expose more hydrolysis sites to be accessible by the enzyme, causing an increase in degree of hydrolysis and bioactivity. The main objective of this work was to review recent advances in food science and technology on the application of HIU for the enhancement of enzymatic hydrolysis of proteins of both animal and plant origin in order to generate novel protein hydrolysates and bioactive peptides which could be used as functional-food ingredients.     

膳食纤维饱腹感的研究进展

作为食品的重要组成部分,膳食纤维已被认为是第七大营养素,具有重要的生理作用。膳食纤维能促进咀嚼,增加唾液的分泌,结合大量的水而使胃部膨胀,水合后粘度增加能够延缓营养物质的吸收和胃的排空,具有回肠刹车作用从而减慢肠道的蠕动。通过这些作用,膳食纤维能够促进机体产生饱腹感;另一方面,膳食纤维能够调节胃肠道中与饱腹感产生相关的激素的分泌,如胰岛素、饥饿素、胰高血糖素样肽-1(glucagon-like-peptide-1,GLP-1)、胆囊收缩素(cholecystokinin,CCK)和YY肽(peptide YY)等。本文概述了膳食纤维饱腹感的研究现状,主要包括膳食纤维对饱腹感的影响、饱腹感的生理指标和主观饱腹感的检测方法等方面。     

Particle size determines foam stability of casein micelle dispersions

The role of interfacial properties and size of casein micelles aggregates on foam stability of casein micelle dispersions (CMDs) was examined. CMDs were prepared by redispersing casein micelles pellets obtained by ultracentrifugation. The size of colloidal particles could be controlled by differences in redispersing temperature. CMDs redispersed at 20 °C (CMD_20 °C) and 4 °C (CMD_4 °C) had average particle sizes of around 200 nm (micelles) and 500 nm (micelles and aggregates), respectively. At 3% total protein, the foam half-life, t_½, of CMD_4 °C was significantly higher than that of CMD_20 °C and skim milk. No correlation between foam stability and surface rheological properties or protein composition could be observed. Foam stability was strongly related to the size of colloidal particles present in CMD. This was confirmed by the observation that the foam stability of CMD_4 °C decreased to that of CMD_20 °C when the aggregates were broken down by homogenisation.     

Diffusing wave spectroscopy and rheological studies of rennet-induced gelation of skim milk in the presence of pectin and κ-carrageenan

The effect of the presence of κ-carrageenan on casein micelle stability and their rennet-induced aggregation was studied using diffusing wave spectroscopy and rheology measurements. Different concentrations of κ-carrageenan, below the gelation regime, were added to skim milk at pH 6.7. No changes in casein stability and on the aggregation kinetics of casein micelles were observed at κ-carrageenan concentrations <0.015% (w/v). The effect of mixing different concentrations of high methoxyl pectin (HMP) (0.04, 0.12 and 0.18%, w/v) with 0.015% (w/v) κ-carrageenan in skim milk was then studied. It was observed that κ-carrageenan protects the system from HMP-induced destabilization. The study of the synergistic effect of κ-carrageenan and HMP on the structuring of casein micelles in milk opens new avenues for the development and control of processes where different mechanisms of aggregation and destabilization occur simultaneously.     

Hydrocolloids with emulsifying capacity. Part 1 – Emulsifying properties and interfacial characteristics of conventional (Acacia senegal (L.) Willd. var. senegal) and matured (Acacia (sen) SUPER GUM™) Acacia senegal

The emulsifying properties and interfacial behaviour of conventional arabic gum (Acacia Senegal, control gum) and after thermal maturation (EM1 and EM2) were studied. All gums presented good oil in water emulsifying capacities. However, after 20–60 high-pressure homogenization passes, matured gums formed more homogenous emulsions with smaller mean oil droplets (0.4 μm) than the control gum (0.65 μm). Modification of pH from 4.5 to 7.0 did not affect sample characteristics. The film-forming capability of all samples at air–water interface was studied using adsorbed and spread techniques. The greater the amount and molecular mass of the arabinogalactan protein (AGP) component in the gum, the better the interfacial properties (tension drop kinetic and interfacial tension final values). Good dilatational elasticity was found for all three gums samples, corresponding to highly elastic interfacial films. The spread films of matured gum EM2 rearranged during compression, passing through liquid expanded, liquid condensed into solid states. Conversely, control and EM1 gums only formed liquid expanded films and smaller surface coverage than EM2. Analytical interfacial results confirm the improved emulsifying properties of matured gums. The properties of the AGP molecules in the gums could be responsible for these differences.     

单宁酸对小麦醇溶蛋白结构及功能性质的影响

采用荧光分光光度计、紫外分光光度计(UV-visible)、傅立叶红外光谱仪(FTIR)等探究单宁酸与小麦醇溶蛋白通过非共价与共价方式结合的机理以及蛋白结构与功能特性的改变。结果表明,在非共价作用下,单宁酸对小麦醇溶蛋白的淬灭类型为生成复合物的静态淬灭作用,两者以氢键作用驱动结合,且以1:1摩尔比结合。同时,在碱性环境下,单宁酸与小麦醇溶蛋白上的自由氨基发生席夫碱反应以共价方式形成复合物。此外,不同条件下,复合物的形成会使得小麦醇溶蛋白三级结构发生去折叠现象、二级结构展开。碱性环境下复合物的形成导致小麦醇溶蛋白二级结构展开程度更高。单宁酸的加入使复合物的抗氧化能力提高,且非共价复合物抗氧化活性更高。在热稳定性方面,两者共价结合使小麦醇溶蛋白的热稳定性提升1.03℃,而两者非共价结合使小麦醇溶蛋白热稳定性降低5.39℃。