Effect of grape pectic enzyme treatment on foaming properties of white musts and wines

White grapes of three different varieties (Macabeo, Xarel.lo and Parellada), which are used in Spanish sparkling wines production (O.A.C. Cava), were treated with a pectic-enzyme preparation on an industrial scale. Foam capacity (foamability (HM), Bickerman coefficient (Σ), foam stability time (TS) and surface tension (ST)) of nine musts from pectic enzyme treated grapes and their corresponding wines were compared to their respective control samples. The HM, Σ, and TS values decreased and ST increased in most of the treated samples. This could be the case, because samples from enzyme-treated grapes had lower protein and polysaccharide contents and higher values of polyphenols than untreated samples: HM and Σ were positively correlated with proteins and polysaccharides and negatively with ST; polyphenol contents had a negative relationship with TS values.     

Comparison of the effects of high pressure homogenization and high pressure processing on the enzyme activity and antimicrobial profile of lysozyme

The effects of high pressure homogenization (HPH, < 190 MPa) and high pressure processing (HPP, < 600 MPa) on hen egg white lysozyme muramidase and antimicrobial activities were assessed. The results showed enzyme activation under mild process conditions (< 120 MPa for HPH and < 400 MPa for HPP, both at 20 °C) and mostly for activity measured at non-optimum pH and temperature. When processes were carried out at 50 °C, lower activation were observed (< 18% for HPH and < 13% for HPP), possibly indicating that processes at 50 °C delivered enough energy to promote undesirable unfolding on lysozyme. HPH induced a greater increase in muramidase activity (29%) than HPP (17%), but this not reflected the antimicrobial performance of the processed lysozyme, since only HPP reduced the minimum inhibitory concentration of the lysozyme against Bacillus cereus (50%) and Geobacillus stearothermophilus (66%). The results highlighted that each process changed differently the lysozyme muramidase and antimicrobial activity.Industrial relevanceHPP and HPH are generally described as technologies able to increase the activity of several enzymes and are suggested as tools to improve the performance of commercial enzymes. The results showed that although HPP and HPH were able to increase the muramidase activity of lysozyme, improvement of the antibacterial performance was only observed for samples processed by HPP. Therefore HPP was highlighted as the better pressure process to physically modify lysozyme.     

超高压技术对肉制品加工的影响

超高压技术是一种先进的食品加工技术。主要介绍了该项技术在肉制品加工的应用情况以及对产品品质的影响。     

Effect of high hydrostatic pressure and thermal processing on the nutritional quality and enzyme activity of fruit smoothies

Fruit smoothie samples were thermally (P₇₀ > 10 min) or high hydrostatic pressure (HHP) processed (450 MPa/20 °C/5 min or 600 MPa/20 °C/10 min) and the total antioxidant capacity (TAC), levels of antioxidant groups [total phenols (TP), anthocyanins and ascorbic acid], instrumental colour, polyphenol oxidase (PPO) enzyme activity and dissolved oxygen were examined over a storage period of 10 h at 4 °C. Thermal processing of smoothies reduced (p < 0.001) TAC and TP values, ascorbic acid and L and a colour attributes (lightness and redness respectively) compared to fresh and HHP-450 processed samples. Conversely, it did result in complete inactivation of PPO enzyme, with no activity detected. Of the HHP treatments, HHP-450 samples had higher (p < 0.001) levels of total antioxidant, phenols and anthocyanin content than HHP-600 samples. However, the latter was more effective in reducing (p < 0.001) the endogenous enzyme activity of the smoothies. .Ascorbic acid content degraded over the storage for all smoothies. HHP-600 samples had high initial values, which declined slowly over storage, while thermal samples had the lowest initial value (0.5 h) that fell below detectable limits by 10 h. Despite these data, less pronounced effects were observed for storage. No significant effects were observed for total anthocyanin and phenolic contents as well as L and colour change (ΔE) variables. Overall, HHP processing of smoothies at moderate temperatures may be a suitable alternative to traditional thermal processing.     

Effects of high pressure on papain activity and structure

Papain was progressively inactivated by increasing pressures in both phosphate (pH 5·0 and 6·8) and Tris (pH 6·8) buffer, but in all systems the effect at pressures up to 600 MPa was minimal and independent of the temperature. However, at 800 MPa, significant losses were found. These losses at 800 MPa were more marked when pressure treatment was at 60°C than when at 20°C. Even though inactivation occurred at 800 MPa, electrophoretic and calorimetric analysis indicated there was little change in size or conformation of the enzyme. The loss in activity, though, was very dependent on the oxygen concentration during pressure treatment, and it is suggested that oxidation of the thiolate ion at the active site, to SO₂⁻ or SO₃⁻, is the major reason for the pressure inactivation of papain. © 1997 SCI.     

Effects of medium high pressure treatments on protease activity

The ability of Lactobacillus manihotivorans LMG 18010 to produce l(+)-lactic acid from a high concentration of starch by direct fermentation was investigated. To improve the production of lactic acid from a highly concentrated starch, fed-batch cultures were carried out with different feeding strategies to reduce substrate inhibition. The highest lactic acid production was 71.4 g/L, which was obtained by intermittent feeding of concentrated starch media containing nitrogen sources. After 5 days of fermentation, about 87% of the substrate was consumed with a volumetric productivity of 0.6 g/L·h which is 1.8 times higher than that obtained from batch fermentation. This result clearly shows that intermittant feeding of a highly concentrated substrate solution during fermentation is an efficient way of eliminating substrate inhibition.     

超高压处理对肉及肉制品的影响

超高压处理应用于肉与肉制品时可降低酶活性,抑制微生物生长繁殖,延长货架期。同时它对肉的色泽、风味、营养成分、蛋白质凝胶、嫩度等也有一定影响。为了推进超高压在肉品中的应用,本文综述了肉及肉制品应用超高压时受到的影响。      

Effects of high pressure processing on lipid oxidation: A review

High pressure processing (HPP) is an alternative mild-technology used in the past decades to sterilize and pasteurize food matrices such as meat and seafood. HPP obeys thermodynamic principles, namely Le Chatelier's law of equilibrium and the isostatic rule, both of which account for microbial inactivation. HPP has the advantage of ensuring reduction of pathogens and spoilage in foods, and preserving the organoleptic characteristics of the product that are compromised in traditional heat treatments. However, high pressure changes the thermodynamic equilibrium of chemical reactions. This is the case of lipid oxidation, in which kinetics is accelerated in the presence of high hydrostatic pressure.In recent years, there has been increasing focus on the response of lipid components to HPP, especially considering the deleterious outcomes that secondary products of oxidation have on the final product. The objective of this work is to review the literature on the effect of this “mild-technology” in the degradation of lipid fraction of foods. We discuss qualitative and quantitative determinations, as well as the thermodynamic and chemical interpretations underlying the phenomenon.Industrial relevanceIn this work we reviewed the literature concerning the effect of high-pressure processing (HPP) on lipid oxidation. Since 1990s HPP has been used as an alternative to thermal treatments to pasteurize and sterilize food products, such as meats and seafood. Many of these raw materials have a high content of lipids (among them trialglycerols and cholesterol-derivative) that are susceptible to oxidation. During the last decade, there has been increasing interest on the response of lipid components to HPP, especially considering the deleterious outcomes that secondary oxidation-derivative molecules have on the final product. This review intends to summarize and discuss the data reported in literature, contextualizing the oxidation within the broad transformation of biological structures due to hydrostatic pressure. A better understanding of the underlying phenomena could lead to the development of predicting models which could be use in food industry.     

High-intensity pulsed electric fields processing parameters affecting polyphenoloxidase activity of strawberry juice

High-intensity pulsed electric fields (HIPEF) were applied to strawberry juice to study the feasibility of inactivating polyphenoloxidase (PPO). Response surface methodology was used to evaluate the effect of HIPEF processing, in which total treatment time (1000 to 2000 μs), pulse frequency (50 to 250 Hz), pulse width (1.0 to 7.0 μs), and polarity (monopolar or bipolar) were the controlled variables at a constant electric field of 35 kV/cm. The proposed 2nd-order response functions were accurate enough to fit experimental results. Strawberry juice PPO was strongly reduced within the range of assayed conditions. HIPEF treatments were more effective in bipolar than in monopolar mode in inactivating PPO. Treatments of longer duration resulted in reductions of the enzyme activity. Moreover, it was feasible to minimize residual PPO activity (down to 2.5%) by selecting bipolar treatments at frequencies higher than 229 Hz and pulse widths between 3.23 and 4.23 μs for a constant total treatment time of 2000 μs.     

Effects of high pressure processing on antioxidant activity, and total carotenoid content and availability, in vegetables

High pressure processing (HPP) is a relatively new food preservation processing technology that enhances food safety and shelf-life without compromising organoleptic qualities. There has been little research on the impact of HPP on the nutritional and health-promoting properties of foods to date and most of it has focused on juices and purees of fruit such as oranges and tomatoes. The objective of this study was to determine the effects of HPP treatment at two pressure levels (400 MPa; 600 MPa) on antioxidant activity, total carotenoid content and carotenoid availability in vitro, of three commonly consumed vegetables. Antioxidant capacity and total carotenoid content differed between vegetables but were unaffected by HPP treatment. In vitro availability of specific carotenoids also varied greatly between vegetables (3–35%). HPP altered availability of carotenoids according to the type of vegetable treated and processing pressure applied, however the magnitude of the responses was minor.

Industrial relevance

This study provides further scientific evidence of the benefits of high pressure processing in retaining the nutritional attributes of fresh foods. Antioxidant activity and levels of carotenoids before and after exposure to high pressures (up to 600 MPa for 2 min) were essentially no different. Also, the data suggest that micronutrients and phytochemicals in certain vegetables may be made more bioavailable by high pressure treatment. From a nutritional perspective, high pressure processing is an attractive food preservation technology and clearly offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products.     

Activation and conformational changes of mushroom polyphenoloxidase by high pressure microfluidization treatment

Activation and conformational changes of mushroom polyphenoloxidase (PPO) after high pressure microfluidization treatment were observed by means of UV spectrophotometer, far-UV circular dichroism, fluorescence emission spectra, UV absorption spectra and sulphydryl groups detection. The results indicated that, treated under pressures of 90 MPa, 110 MPa, 130 MPa and 150 MPa one pass, and 150 MPa 1, 2 and 3 passes, respectively, mushroom PPO exhibited an increase in activity. The circular dichroism (CD) analysis demonstrated that some of secondary structures such as α-helix were destroyed. There were some indices that the increase of relative activity was accompanied by a decrease in α-helix content. The fluorescence emission spectra analysis indicated that Trp and Tyr residues in mushroom PPO were more or less exposed to solvent, and the result was in good agreement with that of UV absorption spectra analysis. The sulphydryl groups detection showed that the sulphydryl groups content on the surface of mushroom PPO was increased.Industrial relevanceResults of the present study show that high pressure microfluidization can not be used to inactivate mushroom PPO. However, it provides a new way for enzyme preparation, such as enzyme modification, with higher activity. High pressure microfluidization can be easily operated, with shorter treatment time and higher food safety compared with chemical methods.     

超高压加工对菊糖果糖转移酶活力和构象的影响

运用高效液相、荧光光谱和圆二色谱等方法研究了超高压加工对菊糖果糖转移酶活力和构象的影响,并分析了压力处理后的酶构象变化与酶活力大小之间的联系。结果表明：在80℃的条件下,与未处理组相比,经压力处理后的菊糖果糖转移酶活力随处理压力的升高及保压时间的延长先上升后下降,200MPa处理30rain后相对酶活力达最高,为124．08％。菊糖果糖转移酶的内源荧光主要来自Trp残基,压力处理后酶的相对荧光强度和相对酶活力之间呈正线性相关,表明酶活力变化与压力处理后的Trp微环境的变化有关。圆二色谱的结果显示该酶仅在219nm有负峰,表明β-折叠是菊糖果糖转移酶的主要二级结构;219nm负峰的峰值大小与相对酶活力呈负线性相关,表明β-折叠是该酶发挥催化活力的结构基础。压力引起酶构象变化的研究为超高压加工提高酶活力的机理研究提供了一定的理论依据．     

Combined effect of high pressure,temperature and holding time on polyphenoloxidase and peroxidase activity in banana (Musa acuminata)

Polyphenoloxidase and peroxidase enzyme activities were evaluated following combined pressure, temperature and holding time treatment in banana (Musa acuminata). Using pressures of up to 110 MPa, temperatures of up to 70 °C and holding times of up to 25 min, based on a 2³ central composite design, the interactive effects were found to significantly influence the activity of both enzymes in prepared banana pulp. Temperature and pressure were found to influence the inactivation of polyphenoloxidase separately, while temperature, pressure and holding time were found to influence the loss of peroxidase in the banana, although no significant interactive effects were found. The reduction in polyphenoloxidase activity was found to be less influenced by the combined treatment than peroxidase activity, thought to be due to solubilisation of the enzyme and effects of the soluble solids content. © 2000 Society of Chemical Industry     

超高压处理在毛蚶脱壳和减菌化中的作用研究

目的明确超高压处理对毛蚶脱壳效果、感官品质以及细菌总数的影响,建立超高压技术在毛蚶加工中的工艺参数。方法以鲜活毛蚶为对照,在250~500 MPa的压力范围内设置6个超高压处理组,根据闭壳肌是否脱离以及壳的完整情况记录毛蚶脱壳效果,通过感官评定、电子鼻气味分析,以及p H、TVB-N、细菌总数等指标的测定评价不同压力处理对毛蚶品质和微生物的影响。结果 300 MPa及以下的处理压力对毛蚶闭壳肌作用小,脱壳效果较差,而450 MPa及以上的压力处理会造成毛蚶壳的破损。毛蚶经超高压处理后,感官评分略有下降,其中350 MPa及以下压力的处理组与对照组之间无显著性差异(P0.05),而400 MPa及以上压力处理组由于气味的变化,对应的感官评分显著降低(P0.05)。超高压处理对毛蚶TVB-N无显著影响(P0.05),300 MPa及以上压力处理组的p H显著升高(P0.05)。毛蚶细菌总数随处理压力的增大显著下降。结论综合考虑脱壳效果、感官品质以及减菌化效果,350~400 MPa的区间范围比较适宜作为毛蚶的超高压处理工艺。     

超高压处理对草莓汁品质酶和杀菌效果的影响

研究了超高压处理对草莓汁多酚氧化酶、果胶甲酯酶和杀菌效果的影响。结果表明:超高压处理对草莓汁具有良好的杀菌效果,微生物随着压力的增加而显著减小,300MPa,15min处理草莓汁,菌落总数和霉菌酵母菌均符合商业无菌条件;草莓汁中PPO和PME比较耐压,中低压条件下,PPO和PME酶活性被激活,随压力增加和时间延长而增大。而中高压处理后,酶活性显著减小(p<0.05),600MPa 25min,PPO及PME残余酶活力分别降至74.6%和47.0%。      

高酶活大豆粉对馒头增白效果的研究

研究了添加高酶活大豆粉对馒头的增白效果,随着添加量的增加,增白效果先提高后降低,当添加量为0.5%时,馒头表面及馒头瓤的L*值、a*值最大、b*值最小、黄色素含量最低,因而增白效果最好。另外,通过控制和面过程的条件:加水量、加水温度、和面时间,得出在加水量50%,加水温度30℃,和面时间17min,能使高酶活大豆粉对馒头的增白效果达到最好。     

超高压处理对腌渍红椒灭菌效果及品质的影响

文中研究25℃条件下不同压力(100、200、300、400、500MPa)及不同保压时间(5、10、15、20、25min)处理对腌渍红椒色泽、质构、相关酶活、微生物等指标的影响。结果表明,随着压力的增加,菌落总数下降明显,在压力≥400MPa时,从7 566 CFU/g降到36 CFU/g以下;果胶酶和过氧化物酶的活性总体处于下降趋势,在100~200MPa压力时,酶活性存在激活现象;辣椒色泽变暗,偏红和偏黄程度加深;Vc含量略下降;硬度和黏着性下降;弹性、凝聚性、回复性和咀嚼性均呈先上升后下降趋势。与热处理组相比,超高压处理对于腌渍红椒有更好的灭菌效果,能在一定程度上钝化酶的活性,同时能较好地保持腌渍红椒的营养成分和质构特性。     

高压CO2对水酶法乳状液破乳影响的研究

研究高压CO2破乳过程中的各种因素对破乳效果的影响,并采用透射电镜来观察乳状液破乳前后油脂和蛋白的变化情况。在单因素基础上通过响应面优化得到最佳破乳条件:高压CO2压力为13.96MPa,温度155.64℃,处理时间21.46 s,浓度0.53 g/cm3,破乳率最优值(94.88±0.30)%。并且通过透射电镜观察发现,破乳前乳状液中大部分油脂被蛋白牢牢包裹,然而破乳后乳状液中包裹油脂的蛋白被破坏,油脂释放并结合在一起。