Profiles and concentrations of heterocyclic aromatic amines formed in beef during various heat treatments depend on the time of ripening and muscle type

Heterocyclic Aromatic Amine (HAA) profiles and concentrations depended on several factors. The largest changes in the HAA profile were observed in meat ripened (chill stored) for 5–10 days. Amines whos concentration varied most prominently included: Phe-P 1, harmane, AαC, IQ, IQx, PhIP, MeAαC, and MeIQx. HAA concentrations were strongly correlated with concentrations of the above compounds. Time of storage significantly affected the HAA profile and concentration. The profile changed dynamically for storage times up to 10 days. For longer times the profile stabilized, only the HAA content increased.A novel, highly precise and accurate HAA analytical method was developed for this study. Results may help to optimize meat processing technology from the point of view of reducing concentration of HAA formed during heat treatment, including the most carcinogenic; IQ, IQx, MeIQx and PhIP amines.     

Improvement of functional properties of acid-precipitated soy protein by the attachment of dextran through Maillard reaction

The functional acid-precipitated soy protein (SAPP)–dextran conjugate was prepared by dry-heated storage at 60 °C under 79% relative humidity (RH) for 5 days through Maillard reaction between the ε-amino of lysine in soy proteins and the reducing-end carbonyl residue in the dextran. The covalent attachment of dextran to SAPP was confirmed by SDS-polyacrylamide gel electrophoresis and gel filtration chromatography. Functional properties of soy protein depend on the structural and aggregation characteristics of their major components (storage globulins 7S and 11S). The conjugate seemed to be predominantly formed by 7S, and the acidic subunits of 11S in soy protein. The emulsifying properties of the SAPP–dextran conjugate were about four times higher than those of SAPP. The solubility of the protein was not enhanced as a result of preheating, but rather it was not decreased when the conjugated protein was heated at 90 °C for 20 min due to the presence of the polysaccharide. The excellent emulsifying properties of SAPP–dextran conjugate were maintained even at pH 3.0 and were further improved at pH 10.0. The object of Maillard reaction is to guarantee the suitable reaction degree, and the resulting soluble conjugate can have excellent emulsifying properties.     

Formation of acid‐precipitated soy protein–dextran conjugates by Maillard reaction in liquid systems

The conjugation reaction between soybean acid‐precipitated protein (SAPP) and dextran in liquid systems via the initial stage of the Maillard reaction was studied. Functional SAPP–dextran conjugates were prepared in 80% ethanol‐reacting system at 50 °C for 6 h, along with 95% ethanol‐reacting system at 60 °C for 24 h. The covalent attachment of dextran to SAPP was confirmed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and gel filtration chromatography.Compared to the classical dry‐heating, the reaction time of glycosylation in the two ethanol systems was largely shortened. Emulsifying activity of SAPP–dextran conjugates obtained by dry‐heating incubation and in ethanol was similar at pH 7.0 and10.0, significantly higher than that of SAPP–dextran mixture or SAPP alone. In addition, SAPP–dextran conjugates obtained in 80% ethanol‐reacting system for 6 h were completely soluble after heating at 90 °C for 20 min. The impact of various processing conditions on the formation of SAPP–dextran conjugates was investigated. This study provides important guidance to create protein–polysaccharide conjugates at mild temperatures in liquid systems.     

Structural characteristics of adsorbed protein and monoglyceride mixed monolayers at the air–water interface

Monolayer technique has been used successfully to study the properties of mixed emulsifiers spread at the air–water interface. In this contribution we are concerned with the analysis of structural characteristics of mixed monolayers formed by milk proteins (β-casein and β-lactoglobulin) and monoglycerides (monopalmitin and monoolein), and how these differ depending on the method used for the formation of the mixed film at the air–water interface (spreading, penetration or by spreading of a lipid into a previously adsorbed protein film). Measurements of the π-A isotherm were obtained in Langmuir- and Wilhelmy-type film balances coupled with Brewster angle microscopy (BAM). The π-A isotherm deduced for adsorbed β-lactoglobulin monolayer in this work is practically the same as that obtained directly by spreading. However, for β-casein the adsorbed monolayer is more condensed than the spread one. For protein–monoglyceride mixed films, the π-A isotherms for adsorbed and spread monolayers at surface pressure (π) higher than the equilibrium spreading pressure of protein (π_e^protein) are practically coincident, a phenomenon which may be attributed to protein displacement by the monoglyceride from the interface. At π<π_e protein and monoglyceride coexist at the interface and the adsorbed and spread π-A isotherms (monolayer structure) are different. Monopalmitin has a higher capacity than monoolein for the displacement of protein from the air–water interface. However, some degree of interaction exists between proteins and monoglycerides and these interactions are higher for adsorbed than for spread films. The topography of the monolayer corroborates these conclusions.     

Growth of hydroxyapatite plate-like nanoparticles by additive free precipitation for the deposition of aligned coatings

In recent years, nanoparticles' morphology has been tailored to tune nanoparticle specific properties for several applications. In particular, plate-like particles have been synthesized to create an analog of nacre microstructure exhibiting outstanding mechanical performance attributed to nacre's micro and nano hierarchy. However, the synthesis of equiaxed hydroxyapatite (HA) plates for constructing an oriented architecture has remained as an astounding challenge. In this study, we designed an additive-free chemical precipitation route in which the pH was increased stepwise to maintain the particles' equiaxed 2d shape. Our results showed that the produced particles exhibited HA's crystal structure and highly sustained the equiaxed/rectangular plate morphology of the octacalcium phosphate (OCP) phase, formed as an interphase during the precipitation. The reaction time, reactant concentration, and heat treatment were found essential in controlling the particles' morphology, size, and crystal symmetry. The crystal features of the particles were dissected via high-resolution scanning and transmission electron microscopes (HRSEM and HRTEM) and X-ray diffraction (XRD) analysis. Moreover, the Williamson-Hall plot and Rietveld Size-strain algorithm were implemented to calculate the crystallite size and strain of the particles. HRSEM and HRTEM micrographs showed that ultrathin (10–20 nm) 2d HA particles with mean lengths of 140–150 nm grew through the c-axis. In the last stage, we attempted to use the particles to deposit oriented coatings by electrophoretic deposition (EPD).     

Optimization of jujube peel pigment multivesicular liposome formulation and evaluation of the protective effect on UVB-induced photodamage

Jujube peel pigment (JP), an ideal natural water-soluble pigment extracted from jujube peel, mainly consists of flavonoids and possesses a wide range of physiological activities. In this study, JP-loaded multivesicular liposomes (JP-MVL) were prepared using the double emulsification method. JP-MVL was characterized, and its encapsulation efficiency was determined using the UV-Vis method. Furthermore, the release behavior and antioxidant capacity of JP-MVL were evaluated in vitro. The results displayed in the structure of JP-MVL were spherical with internal vesicles; the average particle size of JP-MVL was 5.63 μm, and the zeta potential was −69.50 mV. Analysis of the release results indicated that the best-fitting models in PBS (Phosphate buffered saline pH 7.4) and 0.9% NaCl were the Higuchi and first-order kinetic models, respectively. The cytotoxicity of JP-MVL at the appropriate concentrations was negligible and had a good protective effect against UVB-induced photodamage.     

植物基原料游离多酚的提取与分离纯化方法研究进展

多酚是植物基食品原料中的主要次级代谢产物, 具有多种生物活性与药用价值。植物基原料中的游离多酚结构具有多样性, 稳定性也存在差异, 在提取和分离纯化过程中, 由于技术局限或方法不当, 游离多酚易发生降解, 浸提率低、产品纯度低等问题一直是制约其深度开发与广泛应用的瓶颈。结合现代提取分离技术, 针对植物基原料中酚类物质的差异性, 选择个性化的精准提取方案将是一种有效的解决思路。本文总结了近5年游离多酚的提取和分离纯化方法的研究进展, 概述了植物基原料游离多酚的存在形式, 归纳了溶剂萃取等传统方法和超声波、微波、超临界流体等现代技术辅助提取法, 总结了金属离子沉淀、柱层析、吸附树脂、膜分离技术及高速逆流色谱法在分离纯化过程中的应用, 旨在为植物基原料中游离多酚的精准提取及活性物质的个性化开发和高值化应用提供参考。     

花色苷递送系统研究进展

花色苷作为植物中常见的功能色素物质,具有广泛的生理功能。然而,花色苷在加工和贮存过程中稳定性较差,容易发生降解。许多研究报道递送系统可应用于提高花色苷稳定性,进而提高其在体内的生物利用度。本文介绍了花色苷在人体内消化吸收的过程,并综述了目前用于提高花色苷肠道稳定性的几种递送系统,包括蛋白质递送系统、多糖递送系统、脂质体递送系统、复乳体系递送系统以及复合递送系统,以期为功能因子在食物中的进一步开发和利用提供理论依据。     

啤酒废酵母泥综合利用的研究

研究了利用啤酒废酵母泥制备酵母抽提物和β-葡聚糖的相关工艺条件。结果表明,自溶-酶联法是制备啤酒酵母抽提物的理想方法,用该法制备啤酒酵母抽提物的抽提率达68.6%、蛋白质利用率达87.3%,抽提物中蛋白质、游离氨基酸态氮和复合核苷酸的含量分别达10.6%、4.2%和3.9%,远高于普通自溶工艺的技术指标;将自溶后的酵母残渣进一步制备成β-1,3-葡聚糖,通过正交试验获得了其优化的工艺条件:酵母浓度10%、碱浓度2%、反应温度80℃、反应时间4 h、碱处理次数4次。在优化的工艺条件下,β-1,3-葡聚糖得率达26.8%、成品中杂蛋白含量仅0.4%、β-葡聚糖分子质量为158ku。实现了啤酒废酵母泥的综合利用和高值化。