Effect of succinylation on the functional and physicochemical properties of bovine serum albumin

Bovine serum albumin was modijed with succinic anhydride so that 50 or 82% of lysine residues were acylated. The structural alterations caused by modification were examined by pH titration, electrophoretic patterns, circular dichroism, amino acid analysis, and the measurement of amino, sulphydryl and hydrophobic groups. Changes in these physicochemical properties were related to inferior whipping, emulsification and gelling properties of succinylated bovine serum albumin compared with the native protein.     

Effect of thiolation on the physicochemical and functional properties of bovine serum albumin

The effects of the attachment of homocysteine residues, to either 16 or 21 amino groups of bovine serum albumin (BSA), on the physicochemical and functional properties were studied. Both thiolated protein derivatives had a lower isoelectric point, hydrophobicity and α-helix conformation compared with the native protein. Polyacrylamide gel electrophoresis indicated that modification of the proteins resulted in a mixture of products. Thiolation impaired the whipping and gelling properties of bovine serum albumin but there was little change in the emulsification properties. It was concluded that increasing the available sulphydryl groups did not promote disulphide/ sulphydryl interchange reactions leading to enhanced functional properties: on the contrary, the blocking of amino groups was instrumental in impairing the whipping and gelling properties.     

超高压处理对小米粉理化特性的影响研究

对米水比例为1∶1、1∶2(w/w)的小米在600 MPa下分别处理15 min、30 min,探讨不同处理条件对小米粉理化特性的影响。结果表明：与空白组相比,超高压对4组不同样品小米粉颗粒形貌、粒径和晶体特性均有影响。全粉中淀粉颗粒形貌由分散的不规则球体变为与其他物质络合粘结成块结构,颗粒平均粒径显著降低,颗粒整体缩小,晶体结构由天然A型转变为B型,米水比为1∶2时对微观结构影响尤为显著。动态流变表明超高压处理后小米粉糊G’和tanδ均高于原粉,G’’均低于原粉,表明高压处理可提高小米淀粉弹性和黏性,该技术可作为有效的物理改性方法改善小米粉的物理特性。     

Effects of the attachment of small molecules by carbodiimide-mediated condensation on the physicochemical and functional properties of bovine serum albumin

The effects of attaching three small molecules, namely N-butylamide, putrescine and lysine, via the carboxyl groups of bovine serum albumin on its physicochemical and functional properties ere studied. To levels of attachment ere achieved by choice of reaction time. All modified samples had high isoelectric points and ere highly positive hen separated electrophoretically. Partially and extensively modified samples behaved differently in their pH titration curves, their gelation properties and the hipping properties of their lysyl derivatives, in that partially modified samples had high values compared ith the control and extensively modified samples had loer values. This as explicable by to theories: either there is increased electrostatic attraction beteen molecules hose isoelectric points are closer to neutrality, or there is a midpoint here a partial degree of conformational disruption results in superior functional properties. The level of conformational disruption in the extensively modified samples as greater than the optimum, hich resulted in impaired functional properties. An EDC control sample produced ithout added nucleophile as extensively cross-linked intra- or intermolecularly and had impaired functional properties.     

Effects of high hydrostatic pressure on the structure and retrogradation inhibition of oat starch

As a non-thermal processing technology, high hydrostatic pressure (HHP) can be used for starch modification without affecting the quality and flavour constituents. The effect of HHP on starch is closely related to the treatment pressure of HHP. In this paper, we investigated the impacts of HHP treatment pressure (0, 100, 200, 300, 400, 500, 600 MPa) on the microstructure and retrogradation characteristics of oat starch, established the retrogradation kinetic model and elaborated the mechanism of HHP treatment inhibiting the retrogradation of oat starch. Results show that HHP treatment caused the microstructure of oat starch experienced crystallisation perfection (100–300 MPa), crystallisation destruction (400 MPa), crystallisation disintegration and gelatinisation (500–600 MPa). Results of oat starch retrogradation showed that, after treated at 500 MPa for 15 min, the recrystallisation rate of oat starch was reduced, the formation of nuclei at the early stage of oat starch retrogradation suppressed and its nucleation mode was changed from instantaneous to spontaneous, otherwise, the mobility of water in oat starch gel system reduced. Therefore, 500 MPa treated for 15 min can inhibits the retrogradation of oat starch. This study provides theoretical guidance for the application of HHP technology in starch modification and food processing.     

超高压处理对大米蛋白功能特性及结构的影响

以不同压力（200、400、600 MPa）对大米进行超高压处理。研究了超高压处理对大米中谷蛋白功能特性以及清蛋白、球蛋白和谷蛋白结构的影响。结果表明:超高压处理后大米蛋白的功能特性和二级结构均发生变化,不同压力影响效果不同。200 MPa时蛋白质的溶解性、持水性和乳化性提高,持油性降低;400 MPa时持水性和乳化性降低,持油性提高,溶解性升高不明显;600 MPa时溶解性、持水性、持油性和乳化性均降低。超高压处理后清蛋白、球蛋白和谷蛋白的二级结构发生改变,β-折叠结构含量降低,无序结构增多。相关性分析结果表明压力、功能特性和二级结构三者之间存在相关性。      

超高压对食品中微生物的影响

超高压是一种新型食品加工技术,已广泛应用于食品的非热加工。在超高压条件下微生物的细胞壁、细胞膜被破坏,引起细胞形态结构的改变;微生物细胞内的结构蛋白、酶等在超高压条件下被钝化,导致微生物正常的代谢功能和增殖能力被破坏;在超高压条件下微生物的蛋白组和基因组也产生了一定的变化,许多与抗逆有关的蛋白质和基因表达上调。     

Tailoring structure and technological properties of plant proteins using high hydrostatic pressure

The demand for proteins is rising and alternatives to meat proteins are necessary since animal husbandry is expensive and intensive to the environment. Plant proteins appear as an alternative; however, their techno-functional properties need improvement. High-pressure processing (HPP) is a non-thermal technology that has several applications including the modification of proteins. The application of pressure allows modifying proteins' structure hence allowing to change several of their properties, such as hydration, hydrophobicity, and hydrophilicity. These properties may influence the solubility of proteins and their ability to stabilize emulsions or foams, create aggregates or gels, and their general role in stability and texture of food commodities. Commonly HPP decreases the proteins' solubility yet increasing their surface hydrophobicity exposing sulfhydryl groups, which promotes aggregation or gelation or enhance their ability to stabilize emulsions/foams. However, these effects are not verifiable for all the proteins and are immensely dependent on the type and concentration of the protein, environmental conditions (pH, ionic strength, and co-solutes), and HPP conditions. This review collects and critically discusses the available information on how HPP affects the structure of plant proteins and how their techno-functional properties can be tailored using this approach.     

Effects of high hydrostatic pressure on physicochemical and functional properties of walnut (Juglans regia L.) protein isolate

BACKGROUND: Walnut (Juglans regia L.) is a good source of protein that has potential application in new product formation and fortification. The main objectives of this study were to investigate the effects of high hydrostatic pressure (HHP) treatment (300–600 MPa 20 min) on physicochemical and functional properties of walnut protein isolate (WPI) using various analytical techniques at room temperature. RESULTS: The results showed significant modification of solubility, free sulfhydryl content and surface hydrophobicity with increased levels of HHP treatment, indicating partial denaturation and aggregation of proteins. Differential scanning calorimetry and fluorescence spectrum analyses demonstrated that HHP treatment resulted in gradual unfolding of protein structure. Emulsifying activity index was significantly (P < 0.05) increased after HHP treatment at 400 MPa, but significantly decreased (P < 0.05) relative to the untreated WPI with further increase in pressure. HHP treatment at 300–600 MPa significantly decreased emulsion stability index. Additionally, HHP‐treated walnut proteins showed better foaming properties and in vitro digestibility. CONCLUSION: These results suggest that HHP treatment could be applied to modify the properties of walnut proteins by appropriate of pressure levels, which will help in using walnut protein as a potential food ingredient. © 2012 Society of Chemical Industry     

Effects of high hydrostatic pressure treatment on structural,allergenicity, and functional properties of proteins from ginkgo seeds

The effects of high hydrostatic pressure (HHP) treatment on the structural, allergenicity and functional properties of ginkgo seed protein (GSP) were investigated. GSP was treated under pressures of 100, 200, 300, 400, 500, 600 and 700 MPa. Western blotting and ELISA assay revealed that HHP treatment at pressure ranges from 300 up to 700 MPa can significantly reduce the allergenicity of GSP. Meanwhile, SDS-PAGE, MALDI-TOF-MS, CD spectra, fluorescence spectra and UV absorption spectra analysis revealed that, after HHP treatment, the GSP disintegrated into proteins with small molecular weights ranging from 4 to 30 kDa; the secondary structures of α-helices and β-sheet were largely destroyed and turned into random coil; and the UV absorption intensity, surface hydrophobicity and sulfhydryl group (SH) content of GSP were significantly increased. Moreover, the HHP-treated GSP showed markedly improved heat stability and emulsifying properties compared to the untreated GSP.Industrial relevanceAs a traditional food and medicine source, the seeds of Ginkgo biloba were used in china for several thousand years. Ginkgo seeds could be added to desserts, glazed fruit, beverages and tipple, also ginkgo seeds, as a traditional Chinese medicinal material, have been recorded in the Compendium of Materia Medical. Research shows that ginkgo seeds have a relatively high content (10%–15%) of proteins, which possess rich and reasonable composition of amino acids, and much higher content of essential amino acids than the recommended FAO/WHO standard, belonging to the high-quality protein. Ginkgo seeds proteins (GSP) have many biological activities, including anti-oxidation, anti-aging, anti-tumor, and anti-bacterial, so it has high value of nutrition and medicine. However, eating GSP could result in allergic reaction to humans, infant, or children are more sensitive to GSP, the clinical symptoms such as nausea, vomiting, bellyache, diarrhea, dysphoria, exanimation, convulsions, dyspnea, and mydriasis, and sometimes even death can occur.In the study, we used the method of high hydrostatic pressure (HHP) treatments, which can significantly improve the functional properties and reduce the antigenicity of GSP. After the HHP treatment, GSP can be transformed into proteins with small molecular weights ranging from 4 to 30 kDa, the antigenicity of GSP can be reduced by more than 95%, and the heat stability and emulsifying properties of GSP can be markedly improved. Thus, this study is very helpful for designing the hypoallergenic and improved functional GSP, which could have a relevant practical application for their use as base ingredients of food.     

Effect of the attachment of valine residues on the physicochemical and functional properties of bovine serum albumin

The effects of attaching a hydrophobic amino acid residue, valine, to the ?-amino groups (lysine residues) of bovine serum albumin (BSA) on the physicochemical and functional properties were assessed. The valyl groups were attached using an N-carboxyvaline anhydride derivative. The valine content of BSA was increased from 27 mol mol^?1 protein to 47·91 or 53·72 mol mol^?1. The number of lysine residues acylated was dependent on the pH of the reaction mixture as was the degree of polyvalylation. Attachment of polyvalyl chains resulted in improved whipping and gelling properties compared with a control sample of ultrafiltered BSA, and interfered with the formation of α-helices. Hydrophobicity measurements using the fluorescent probe cis-parinaric acid revealed increased hydrophobicity values only after the modified samples had been heat denatured.     

Effects of high hydrostatic pressure on the physicochemical and emulsifying properties of sweet potato protein

The influence of high hydrostatic pressure (HHP) treatment on the physicochemical and emulsifying properties of sweet potato protein (SPP) at various concentrations, e.g. 2%, 4% and 6% (w/v, SPP‐2, SPP‐4 and SPP‐6), was investigated. Significant differences in hydrophobicity, enthalpy of denaturation and solubility were observed (P < 0.05). Emulsifying activity indexes (EAI) of SPP‐2 and SPP‐6 increased at 400 MPa, whereas EAI of all SPP significantly decreased at 600 MPa (P < 0.05). Emulsion stability (ESI) was significantly decreased for SPP‐2 and SPP‐6, while increase in ESI was observed for SPP‐4 above 200 MPa (P < 0.05). SPP‐2 emulsions showed sharp decrease in apparent viscosity with pressure increase, while pseudo plastic flow behaviour was not changed for all of emulsions. Sporamins A and B were well‐adsorbed in pressurised emulsion without displacement. These results suggest that HHP treatment could be used to modify the physicochemical and emulsifying properties of SPP.     

高静压加工对山竹汁微生物及品质的影响

利用高静压(high hydrostatic pressure,HHP)技术对山竹果汁中的微生物和果汁品质进行研究。结果表明:经400 MPa,10 min和500 MPa,5 min的HHP处理后,山竹汁中的自然菌群全部被杀灭,而山竹汁的颜色、糖度、酸度等理化指标,以及其中的VC、总酚含量和抗氧化活性等营养品质,未发生显著的变化(P>0.05)。     

Effect of high hydrostatic pressure on the structure,physicochemical and functional properties of protein isolates from cumin (Cuminum cyminum) seeds

The effect of high hydrostatic pressure (HHP) treatment on the structure, physicochemical and functional properties of cumin protein isolate (CPI) was investigated. More aggregates, pores, irregular conformations and bigger particle size were observed for HHP-treated CPI. HHP resulted in an increase in α-helix, a decrease in β-strand and fluorescence intensity of CPI. Surface hydrophobicity (H_o) of CPI significantly increased after HHP treatment, from 343.35 for native CPI to 906.22 at 600 MPa (P < 0.05). HHP treatment at 200 MPa reduced zeta-potential and solubility of CPI, while had little effect at 400 and 600 MPa. Emulsifying activity and stability of CPI decreased after HHP treatment, of which droplet size of emulsions significantly increased (P < 0.05). HHP-treated CPI could form heat-induced gelation at lower temperature (68.5 °C) and improved storage modulus (G′) comparing to native one (80.6 °C), suggesting that CPI might be potential protein resources as gelation substitute in food system.     

Effect of gamma-irradiation on the molecular properties of bovine serum albumin

To investigate the effect of oxygen radicals on the molecular properties of bovine serum albumin (BSA), the secondary and tertiary structures, molecular weight and optical anisotropy of BSA were examined after the irradiation of the protein at various doses. gamma-Irradiation of the protein solution caused the disruption of the ordered structure of protein molecules as well as degradation, cross-linking and aggregation of polypeptide chains. Fluorescence spectroscopy indicated that irradiation quenched the emission intensity excited at 280 nm. Fourier transform infrared spectroscopy (FTIR) indicated that irradiation caused transformation from beta-turns into beta-sheets. A light scattering study showed that increasing the radiation dose decreased the molecular weight of the protein. Optical anisotropy data showed that radiation changed the ordered structure of the protein. Ultraviolet absorption spectroscopy indicated that fragmentation and aggregation might occur in response to radiation exposure.     

超高压对牛乳清蛋白水解影响的研究进展

主要综述了国内外关于超高压处理对牛乳清蛋白水解及其产物功能特性影响的研究进展,并展望了超高压处理在酶法制备乳清蛋白生物活性肽方面的应用前景。      

Physicochemical and functional properties of cowpea protein isolates treated with temperature or high hydrostatic pressure

The effect of thermal (TT, 70 and 90 °C) and high hydrostatic pressure (HHPTs, 200, 400 and 600 MPa) treatments on physicochemical and functional properties of cowpea protein isolates (CPIs) extracted at pH 8.0 (A8) and pH 10.0 (A10) was analyzed. The pH of protein extraction affected some physicochemical properties (surface hydrophobicity (Ho) and denaturation temperature), without affecting the functional properties. Treatments led to the formation of soluble protein aggregates stabilized by disulfide bonds, especially with TT at 90 °C. TT and HHPTs shifted the wavelengths of maximum emission to red and to blue, respectively. All treatments induced unfolding and denaturation. HHPTs was more efficient than TT to enhance gelation and water holding capacities. Interestingly, treated and untreated CPIs exhibited high values of solubility (72–97%). TT and HHPT induced greater changes in physicochemical and functional properties of A8 than in those of A10. Remarkably, functional properties were improved from the less energetic treatments (70 °C, 200 MPa).Industrial relevanceThe comparison between treatments (one traditional and one corresponding to an emerging technology) gives information about the possibility of obtaining modified proteins for different functional purposes. The modified cowpea protein isolates may be used in beverages because of high solubility, in desserts because of gel formation capacity and/or as additives in other foodstuff because of improved water holding capacity. This knowledge would increase the added value of a local production currently marketed without processing.     

Cycled high hydrostatic pressure processing of whole and skimmed milk: Effects on physicochemical properties

In this study, we compare the effects of single- and double-cycle HP treatments at 600 MPa on inactivation of the natural microflora and physicochemical properties of whole and skimmed milk of high bacterial load. The results show that two-cycled HP (2 × 2.5 min) was more effective (P < 0.05) on microbial inactivation, and caused similar or slightly less changes (P > 0.05) in physicochemical properties of milk in comparison to single cycled HP (1 × 5 min). In addition to the expected milk protein structure changes, HP at 600 MPa caused only slight effects on milk fat and lactose. Minor decreases in levels of short chain fatty acids were observed with the cycled treatments, and the volatiles in general decreased after HP treatment, depending mostly on the pressure time but also on cycling in skimmed milk. The study confirmed the superior effect of two-cycle HP on microbial inactivation, and shows a slightly better preservation of the physical-chemical milk quality.Industrial relevanceMulti-cycling HP has been shown to be advantageous for microbial inactivation, but limited information is available regarding the effect on milk components in whole milk or skimmed milk. The present study compares the psychochemical properties of whole and skimmed milk processed by multi-cycling in comparison to single cycle HP treatment. Double cycled HP presented a superior effect on microbial inactivation and slightly better preservation of milk quality than one continuous HP.     

超高静压对食品热力学特性的影响

超高静压技术是21世纪食品工业大力提倡和发展的高新技术之一。在食品的超高静压处理中,由于压缩做功使其温度发生改变,导致压致升温现象的产生,而要了解食品在超高静压下的温度变化,须知道与压力有关的这些食品的热力学特性。本文综述了在超高静压处理中食品热力学特性的测定方法及高静压对这些热力学特性的影响。