Changes in protein-protein and protein-polysaccharide interactions induced by high pressure

β-Lactoglobulin and bovine serum albumin (BSA) protein solutions (0.1%, 0.2% and 2.5%), when subjected to high pressure treatment (800 MPa for 20 min) at neutral pH, were denatured and some aggregates formed. The total calorimetric enthalpy of 2.5% solutions of the pressure-treated proteins decreased to virtually zero for both β-lactoglobulin and BSA following pressure treatment. Isoelectric focussing patterns (IEF) indicated that aggregation occurred in both proteins and there was a concomitant loss of sulphydryl groups (42% for β-lactoglobulin and 55% for BSA), suggesting that protein aggregation after high pressure processing was caused, at least in part, by the formation of -S-S- bridges. The surface hydrophobicity of the two proteins was modified, increasing (40%) with β-lactoglobulin and decreasing (41%) with BSA. Pressure treatment of 1:1 mixtures of BSA and dextran sulphate (DS) yielded structures with a significant enthalpy. However, addition of DS to β-lactoglobulin had little effect on the thermograms, suggesting that the DS either protects the protein against pressure induced unfolding or enables the pressure-denatured protein to regain some secondary structure.     

Relationship between functional properties and aggregation changes of whey protein induced by high pressure microfluidization

Aggregation changes of whey protein induced by high-pressure microfluidization (HPM) treatment have been investigated in relation with their functional properties. Whey protein was treated with HPM under pressure from 40 to 160 MPa. Functional properties (solubility, foaming, and emulsifying properties) of whey protein concentrate (WPC) ultrafiltered from fluid whey were evaluated. The results showed significant modifications in the solubility (30% to 59%) and foaming properties (20% to 65%) of WPC with increasing pressure. However, emulsifying property of WPC treated at different pressures was significantly worse than untreated sample. To better understand the mechanism of the modification by HPM, the HPM-induced aggregation changes were examined using particle size distribution, scanning electron microscopy, and hydrophobicity. It was indicated that HPM induced 2 kinds of aggregation changes on WPC: deaggregation and reaggregation of WPC, which resulted in the changes of functional properties of WPC modified by HPM.     

Changes in textural and rheological properties of gels from tilapia muscle proteins induced by high pressure and setting

Tilapia meat pastes were prepared with a combination of hydrostatic pressure (200 MPa) and setting (50 °C) treatments, to investigate the changes in their rheological properties, gel-forming ability, whiteness and protein solubility of their gels. The control, a cooked gel (90 °C/30 min), was elastic and white, with low gel-forming ability. Gels formed by setting were elastic, rigid and mainly consisted of covalent bonds. Gels formed by pressurisation were soft and consisted of hydrogen bonds and hydrophobic interactions. Pressurisation prior to setting reinforced the gel structures, by formation of both covalent and non-covalent bonds. Setting prior to pressurisation did not alter the characteristics of the gel. Setting under pressurisation constructed a viscous gel with non-covalent bonds. Various fish gel products were formed in this study.     

Changes in the composition of hop secondary metabolites induced by high hydrostatic pressure

Hops contain large amounts of secondary metabolites, many of which have notable bioactive and sensory characteristics. Many of these properties are affected by the processing of raw hops into products. We studied the influence of high‐pressure processing (HPP) on the content and composition of secondary metabolites in hop homogenates prepared from fresh green cones of several Czech hop varieties. Homogenates contained more hop oils (27% on average) compared to dried hops. The composition of essential oils in homogenates after HPP showed a decrease in fatty acid methyl and thioesters fractions (80 and 100% respectively). Conversely, the number of other bioactive compounds from the group of resins and prenylflavonoids that remained in HPP homogenates was retained to a greater extent than in the dried hops. Low temperatures and an oxygen‐free atmosphere were effective conditions for the preservation of raw hops and hop products. Copyright © 2018 The Institute of Brewing & Distilling     

Effect of high pressure treatment on the physicochemical and functional properties of egg yolk

The effects of high-pressure (HP) treatment at 100–500 MPa on some physicochemical and functional properties of egg yolk (EY) were investigated. Protein solubility, viscosity, surface hydrophobicity (H₀), free sulfhydryl (SH) content, differential scanning calorimetry characteristics, emulsifying activities and emulsifying stability were evaluated. HP-treatment resulted in protein aggregation, as evidenced by gradual decrease in protein solubility and significantly increased in viscosity. HP-treatment at 100–500 MPa induced a gradual decrease in H₀ and SH content, possibly due to protein unfolding and subsequent aggregation/re-association of unfolded proteins. Emulsifying activity index (EAI) was slightly decreased between 100 and 300 MPa and when the pressure is above 400 MPa, EAI was significantly (P < 0.05) decreased relative to the untreated EY. HP-treatment at 100 MPa significantly (P < 0.05) increased the ESI values of EY, while a significant (P < 0.05) decrease was observed when the pressure was above 200 MPa. It was also investigated that there are significant correlations between physicochemical properties of EY, and the differences in the modification of EY protein by HP treatment at different pressure levels may be attributed to the differences in aggregation and unfolding/refolding extents of proteins.     

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。      

Changes induced by high hydrostatic pressure in acidified and non-acidified milk during Oaxaca cheese production

Oaxaca cheese, produced using the pasta filata method, is a very popular Mexican dairy products. In this work, the effect of high hydrostatic pressure (HHP) and the acidification process before and after HHP treatment of raw cow milk was studied at different pressure levels (150, 300 and 500 MPa) and holding times (10 and 30 min). Clotting time, proximal composition, microstructure, secondary protein structure and electrophoretic profile were evaluated. HHP did not influence clotting time in samples acidified before HHP, but it appears to have a positive effect at lower pressure treatments on non-acidified milk. Moisture, protein and fat were similar in cheeses treated at most HHP conditions regardless of the acidification. HHP did not influence the microstructure of cheese and the secondary structure of proteins. The use of HHP during the manufacture of Oaxaca cheese allowed preserving quality parameters evaluated without advantages in processing time and the product's proximal composition.     

Viscoelastic properties of high pressure and heat induced tofu gels

Tofu gels were rheologically examined to determine their storage or elastic (G′) and loss or viscous (G″) moduli as a function of frequency within their linear viscoelastic limits. The tofu gels were made using either glucono-δ-lactone (GDL) or calcium sulphate (CaSO₄·2H₂O), followed by either heat treatment (heated soymilk at ?97 °C prior to coagulation and subsequently held at 70 °C for 60 min, HT) or high pressure treatment (400 MPa at 20 °C for 10 min, HP). The overall moduli values of the GDL gels and CaSO₄·2H₂O gels of both physical treatments were similar, each gave frequency profiles expected for weak viscoelastic materials. However, although both temperature and high pressure treatments could be used to produce tofu gels, the final products were not the same. Pressure formed gels, despite having a higher overall “consistency” (increasing values of their moduli), had a proportionately higher contribution from the loss modulus (increased tan δ). Differences could also be observed using confocal scanning laser microscopy. While such treatment may give rise to differing systems/structures, with new or modified organoleptic properties, the more “open” structures obtained by pressure treatment may well cause processing difficulties if subsequent reworking or moulding is required.     

Changes in aromatic volatile composition of strawberry after high pressure treatment

The aromatic volatile compounds of high pressure treated strawberry coulis (Fragaria ananassa Gariguette) were analysed by capillary gas chromatography–mass spectrometry (GC–MS) and compared with aromatic volatile compounds of raw strawberry and heat-treated strawberry coulis. Characterisation of treated and untreated samples was achieved by applying principal component analysis to the chromatographic data. Aroma of strawberry was specifically identified by furaneol (2,5-dimethyl-4-hydroxy-furan-3-one) and nerolidol (3,7,11-trimethyl 1,6,10-dodecatrien-3-ol). No significant changes of all the aromatic volatile compounds were observed between untreated and high pressure-treated (200 and 500 MPa, 20°C, 20 min) strawberry coulis. On the other hand, changes appeared in the composition of aromatic compounds after an ultra high hydrostatic pressure treatment at 800 MPa (20 min, 20°C) and after a sterilisation (120°C, 20 min).     

高压均质对大豆分离蛋白功能性质的影响

为了了解高压均质技术对大豆分离蛋白（SPI）功能性质的影响,采用不同的均质压力、均质次数和料液比对大豆分离蛋白溶液进行了高压均质处理,并分析处理前后SPI功能性质的变化.结果表明：高压均质可在一定程度上提高SPI的溶解性、乳化活性及其稳定性和起泡性及泡沫稳定性.均质压力在0～70 MPa的范围内升高时,SPI的溶解性、乳化稳定性、起泡性和泡沫稳定性得到了相应的改善,而乳化活性在压力为40 MPa时达到最高;均质次数由1次向3次增加时,SPI的乳化稳定性、起泡性及泡沫稳定性得到了提高,而溶解性和乳化活性则降低;均质物料料液比在1∶16～1∶8 （g∶mL）的范围内逐步增大时,SPI的各项功能性质均有不同程度的提高,并在料液比为1∶8时达到了最高值.     

高静压处理对魔芋葡甘聚糖/大豆分离蛋白复合溶胶特性的影响

为考察高静压对多糖-蛋白质复合体系功能特性的影响,以魔芋葡甘聚糖和大豆分离蛋白为原料,研究不同压力、不同时间下高静压处理对两者复合溶胶的乳化活性、乳化稳定性、黏度特性以及微观结构的影响。研究结果表明,在400 MPa压力下经不同的处理时间,复合溶胶的功能性质均有显著性提高,其中乳化活性、乳化稳定性在处理10~15 min时达到最佳,与空白组相比分别提高了5.6%~6.2%和2.5%~2.7%,而黏度则在400 MPa/15 min时达最高值,比空白组提高了145.3%。同时扫描电镜分析得出,适当高静压处理可使多糖和蛋白质复合溶胶体系形成更加均匀致密的三维网络结构,二者间相互作用增强。     

Changes in purified tomato pectinmethylesterase activity during thermal and high pressure treatment

The enzymatic reaction of purified tomato pectinmethylesterase on pectin was investigated during a combined high pressure/temperature treatment (0.1–600 MPa/20–65 °C) at pH 8.0 and pH 4.4. The optimal temperature for tomato pectinmethylesterase activity at atmospheric pressure is situated around 45 °C at pH 8.0, and around 35 °C at pH 4.4. At both pH 8.0 and pH 4.4, the optimal temperature shifted to higher values at elevated pressure compared with atmospheric pressure. At both pH values, the catalytic activity of tomato pectinmethylesterase was higher at elevated pressure than at atmospheric pressure, creating possibilities for rheology improvements by pressure processing. Maximal tomato pectinmethylesterase activity in the pressure–temperature domain investigated was observed at 55 °C and 300 MPa for pH 8.0 and at 57 °C and 450 MPa for pH 4.4. However, under all pressure–temperature conditions tested the catalytic activity of tomato pectinmethylesterase at pH 4.4 was much lower than at pH 8.0. The chemical de‐esterification of pectin at pH 8.0 was accelerated by increasing pressure and temperature, whereas no chemical deesterification of pectin was observed at pH 4.4. Copyright © 2004 Society of Chemical Industry     

Micellar changes induced by high pressure. influence in the proteolytic activity and organoleptic properties of milk

We investigated the effects of high-pressure treat-of 25 to 60 degrees C, on micelle structure, proteolytic activity, and sensory properties of milk. Pressure treatments at 25 degrees C considerably reduced micelle size, while pressurization at higher temperatures progressively increased micelle dimensions. Pressure-induced denaturation of beta-lactoglobulin (beta-LG) amounted 76% at 25 degrees C and was almost 100% in milks treated at 40 to 60 degrees C. alpha -Lactalbumin (alpha-LA) was resistant to pressure at temperatures up to 40 degrees C, but its denaturation reached 56% at 60 degrees C. Plasmin resisted pressurization at room temperature; however, pressure treatments at higher temperatures increased plasmin inactivation, which reached 86.5% at 60 degrees C. Pressurization at temperatures from 40 to 60 degrees C reduced the proteolytic activity and improved the organoleptical properties of milk, compared with the same treatments at 25 degrees C, which suggested that these combined treatments could be used to produce milk of good sensory properties with an increased shelf life. These results are discussed in the light of the changes found in micellar structure.     

Changes in rheological behaviour and functional properties of hen's egg yolk induced by processing and fermentation with phospholipases

Functional changes of hen's egg yolk rheological behaviour as a result of processing (pasteurisation, freeze-drying) and modifying its phospholipids using phospholipase A₁ (PLA₁) and phospholipase A₂ (PLA₂) were studied. It could be shown how fermentation with phospholipases affects the different steps of heat-induced gelation of egg yolk. As a consequence of fermentation of native yolk with 0.1% PLA₁, the first viscosity maximum was shifted from 79 to 97 °C. In fermented pasteurised yolk, the homogenous gel-like consistency from the first viscosity maximum was even stabilised up to 100 °C. The second viscosity ascent, which indicates solid gel structures (caused by aggregation of denatured proteins), was prevented entirely. In contrast to pancreatic PLA₂, fermentation of egg yolk with microbial PLA₁ resulted in a hydrolysis of approximately 78% of phosphatidylethanolamine and a significant change in flow behaviour (of yolk solutions).     

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。     

Effect of high pressure processing on structural and functional properties of canned aquafaba

Food Science and Biotechnology - Aquafaba is chickpea cooking water. It has great functional properties since it consists of starch and protein. High pressure processing (HPP) is proven to modify...     

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.     

Antibody binding and functional properties of whey protein hydrolysates obtained under high pressure

This paper examines the potential of high hydrostatic pressure to produce whey protein hydrolysates that combine low immunoglobulin (Ig)G- and IgE-binding with acceptable functional properties, with the aim to produce milk-based ingredients with reduced potential allergenicity that could be used in hypoallergenic foods. Treatment with pepsin and chymotrypsin under high pressure produced, in minutes, hydrolysates in which α-lactalbumin and β-lactoglobulin were totally proteolysed, giving rise to large and hydrophobic peptides. Such hydrolysates presented reduced antigenicity and human IgE-binding properties. The hydrolysates obtained with pepsin at 400 MPa showed improved heat stability, particularly at a pH, close to the isoelectric point of the whey proteins, and their emulsion activity indexes at pH 7.0 were superior to those of the untreated whey proteins. These results suggest that the peptides present retained low antigenicity together with sufficient capacity to form emulsions.     

Determination of carbendazim and thiophanate-methyl residues in some vegetables and fruits by high pressure liquid chromatography

Summary A simple method is described for the quantitative determination of carbendazim and thiophanate-methyl. The fungicides are extracted with methanol and the extracts are successively filtered through a C 18-Sep-pak cartridge and a basic aluminium oxide column. Ten samples can be analysed in about three hours by means of reversed-phase liquid chromatography.

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Bestimmung von Carbendazim und Thiophanate-methyl in Gemüse und Obst durch Hochdruck-Flüssigkeits-Chromatographie

Zusammenfassung Eine einfache Methode für die quantitative Bestimmungen von Carbendazim und Thiophanat-methyl in Gemüse und Obst wird beschrieben. Die Fungicide werden mit Methanol extrahiert und anschließend durch C 18-Kieselgel und eine basische Aluminiumoxidkolonne filtriert. Zehn Proben können in etwa 3 Std durch Umkehrphasenchromatographie analysiert werden.