超高压和酶抑制剂对山药泥中多酚氧化酶活性的影响

本文采用超高压、温度和酶抑制剂单独和复合处理山药泥，对山药泥中多酚氧化酶活性和色泽变化进行了研究。结果表明，山药泥中多酚氧化酶(PPO)最适作用温度为35℃。压力400MPa、温度20℃时，PPO的活性有一个峰值，当压力大于或小于400MPa，PPO的活性都明显减弱，600MPa时PPO活性最弱。对山药泥进行温度、压力、时间的L9(3^4)正交试验结果表明：在550MPa、40℃下处理10min后，PPO活性最弱，抑制效果最佳。通过酶抑制剂正交试验筛选出最佳PPO抑制剂配方为：0．05％柠檬酸 0．4％抗坏血酸 0．02％EDTA。用超高压(550MPa)和酶抑制剂共同处理山药泥，不仅抑制了PPO活性，而且保持了山药泥原有的色泽。     

超高压处理对芒果泥品质的影响

为了提升芒果泥的品质,本研究采用了超高压、辐照和低温等离子三种非热加工手段对芒果泥进行处理,并对不同方法的杀菌效果进行分析比较。选取其中较优的方法（超高压）,进一步研究其对芒果泥的色度、感官、可溶性固形物含量以及储藏稳定性的影响。结果表明,超高压（≥200 MPa）和辐照（≥3 kGy）处理均对芒果泥有良好的杀菌效果,果泥的菌落总数均≤2 lg(CFU/g),达到商业无菌标准。但低温等离子处理效果不理想,当处理时间≤6 min时,果泥中的菌落总数均未达到商业无菌标准。超高压处理后芒果泥的口感与对照样品较为接近。大于500 MPa的压力处理后,芒果泥的储存期稳定性较好,特别是用600 MPa处理后的样品,其储存期至少可以达到9个月。这一结果表明,超高压可以在杀灭芒果泥中有害微生物提高芒果泥稳定性的同时,最大限度地保持芒果泥的原有品质。本研究为超高压技术在食品加工中的应用提供了一定的理论依据和方法指导。     

超高压处理对复合山药泥贮藏期间品质变化的影响

该研究以山药、秋葵、猕猴桃为原料制备得到的复合山药泥为研究对象,对比分析了超高压（High Hydrostatic Pressure,HHP）处理（400 MPa/5 min,400 MPa/10 min,500 MPa/2 min）和热处理（Thermal processing,TP）（97 ℃/2 min）对复合山药泥在4 ℃下贮藏24 d中微生物、营养成分、抗氧化性、内源酶活性及粒径等品质指标的影响。结果表明,贮藏期间,HHP能很好地抑制微生物生长,400 MPa/5 min和500 MPa/2 min处理样品菌落总数均小于1 lg CFU/g,且所有处理样品中均没有霉菌和酵母菌检出;相比于TP处理,HHP处理后的复合山药泥的总酚含量提高了60.66%~227.54%,因此在贮藏期间其抗氧化能力相对更强;贮藏期间,HHP组的?E显著小于TP组,24 d后TP组的?E达到了25.26,而500 MPa/2 min组仅为5.44,因此HHP处理更能维护复合果蔬泥在贮藏期间的色泽。但是,由于不能有效抑制PME的酶活,HHP处理组在贮藏期间的粒径和黏度均高于TP处理。综上,HHP处理能够满足复合果蔬泥的商业应用需求,但对内源酶活性的抑制效率不高。     

Polyphenoloxidase Activity and Color of Blanched and High Hydrostatic Pressure Treated Banana Puree

The effects of blanching and high hydrostatic pressure (HHP) treatments on natural flora evolution, polyphenoloxidase (PPO) activity and color of banana puree adjusted to pH 3.4 and water activity (a_w) of 0.97 were evaluated during 15 days storage at 25°C. Standard plate as well as yeast and mold counts of HHP treated purees were <10 CFU/g throughout storage. Blanching time was found to affect (P<0.05) puree color. HHP treatments retained the initial color of the banana purees. Longer browning induction times and slower browning rates were observed when a longer blanching time was combined with a 689 MPa pressure treatment. A residual PPO activity < 5% was observed in the puree when a 7 min blanch was followed by HHP treatment at 689 MPa for 10 min.     

超高压处理对复合苹果泥微生物和品质的影响

本研究以苹果、猕猴桃、胡萝卜为原料制备复合苹果泥,对不同配比的样品进行感官评价以确定最佳配比,并研究超高压(High Hydrostatic Pressure,HHP)处理参数(处理压力、保压时间)对样品微生物和品质的影响。通过感官评定确定苹果:猕猴桃:胡萝卜最佳配比为6:2:1,通过筛选确定超高压杀菌参数为400 MPa/2 min和500 MPa/2 min。结果表明,HHP样品的可溶性固形物、膳食纤维、总类胡萝卜素和β-胡萝卜素含量与热处理之间没有显著性差异(P>0.05);HHP样品具有更好的色泽和更高的抗坏血酸含量及抗氧化能力,其中抗坏血酸含量在0.75~0.83 mg/100 g,而热处理仅为0.55 mg/100 g;同时HHP样品黏度更高,表面积平均粒径更小。超高压处理对样品中多酚氧化酶(Polyphenol Oxidase,PPO)和果胶甲酯酶(Pectin Methylesterase,PME)的钝化能力比热处理弱,残存酶活分别为56.70%~65.54%和82.08%~86.91%,而热处理则为38.04%和81.89%。因此超高压处理能够更好地保证复合苹果泥的理化特性和营养品质,但对酶活的钝化能力不强。     

Thermophysical properties of mango pulp (Mangifera indica L. cv. Tommy Atkins)

The density, heat capacity and thermal conductivity of mango pulp (Mangifera indica L. cv. Tommy Atkins) were determined at moisture contents of between 0.9 and 0.52 kg kg⁻¹ (w.b.) and temperatures of between 20 and 80 °C. The experimental data were satisfactorily fitted (explained variation values >99.1%) as functions of the moisture content and temperature by using multivariate linear models. In the range of conditions considered, the moisture content exhibits a greater influence on the studied properties than temperature.     

Enzyme Activity and Nutritional Quality of Peach (Prunus persica) Juice: Effect of High Hydrostatic Pressure

The inactivation of polyphenol oxidase and pectin methylesterase in peach juice was investigated after high hydrostatic pressure processing at 400–600 MPa and 25°C for 5–25 min, respectively. At 400 MPa, polyphenol oxidase and pectin methylesterase were activated by 7.3 and 2.6%. At 500 and 600 MPa, polyphenol oxidase and pectin methylesterase were inactivated significantly with increasing the pressure and time, and the inactivation kinetics was fitted by the first order model. Moreover, some physio-chemical properties were studied. The results revealed that high hydrostatic pressure treatment preserved more L-ascorbic acid and maintained the color and sensory quality better than thermal treatment.     

超高压对菠菜浆贮藏期间颜色变化的影响

为探究超高压技术（HHP）处理菠菜浆的颜色品质在不同贮藏条件下的变化规律,对HHP处理样品的CIEL’a’6’颜色进行测定。结果表明,HHP处理菠菜浆在处理后和贮藏期与传统热处理菠菜浆相比其颜色品质更好。在4~C下进行贮藏,HHP处理样品的一a‘值和h。值均显著高于热处理样品,并且在贮藏期阀基本保持不变;￡_’值在HHP处理后显著增加,在贮藏过程中亦基本保持不变,色泽更为明亮。在27。C下进行贮藏,HHP处理样品的一a’值和h。值均显著高于热处理和未处理样品,并在贮藏期间呈下降趋势;上’值在贮藏过程中呈现曲折上升的趋势。因此,HHP处理菠菜浆的表观绿色在冷藏和室温贮藏条件下均要好于传统热处理。HHP处理可以在一定程度上保持绿色菠菜浆的颜色品质,减缓其颜色品质的劣变。     

超高压和高温瞬时杀菌对蓝莓汁品质影响的比较

主要研究了2种杀菌方式对蓝莓汁品质的影响。一种是550 MPa、5 min的超高压杀菌,另一种是121℃、5 s的高温瞬时杀菌。通过测定杀菌后蓝莓汁的菌落总数、悬浮稳定性、色差值、花色苷含量和理化性质等指标,证实超高压杀菌在杀菌的同时较好地保持了蓝莓汁原有的品质、色泽及营养。     

不同杧果品种对杧果酵素品质的影响

以‘金煌杧’、‘凯特杧’、‘红象牙杧’3 种杧果为原料制备杧果酵素,通过测定发酵过程中的感官、可溶性固形物含量、pH 值、总酸、还原糖、总酚含量和超氧化物歧化酶（superoxide dismutase,SOD）酶活力等指标,探究不同杧果品种对杧果酵素品质的影响。结果表明：根据3 组杧果酵素发酵过程中的指标变化可以发现,发酵72 h 时品质最佳;与‘凯特杧’、‘红象牙杧’相比,‘金煌杧’杧果酵素在发酵72 h 时的感官评分（92）、可溶性固形物含量（8%）、还原糖含量（1.51 mg/mL）、总酚含量（0.308 mg/mL）以及SOD 酶活力（36.6 U/mL）均最佳,因此‘金煌杧’是制作杧果酵素的最佳原料。     

Effect of Soluble Solids Concentration and Temperature on Thermo-Physical and Rheological Properties of Mango Puree

Thermo-physical and rheological properties of mango pulp were evaluated at different temperatures (20, 40, 60, and 80°C) and total soluble solids concentrations (15, 20, 32, and 40°Brix). Thermal properties were primarily dependent on the moisture content of the sample, and increased with temperature and decreased with soluble solids concentrations. Density showed a reverse trend. Glass transition temperatures increased with an increase in soluble solids concentrations indicating better stability. Empirical models developed for each thermal property as a function of temperature and soluble solids concentrations (R² > 0.90) generally showed better predictions than published models. Mango puree exhibited pseudo-plastic behavior during steady shear measurements, and the power law model well described their flow behavior. Consistency coefficient increased with soluble solids concentrations and decreased with temperature. The flow behavior index ranged between 0.27 and 0.38 but did not show a clear trend either with soluble solids concentrations or temperature. Small amplitude oscillatory shear measurements revealed that mango puree behaved like a weak gel and demonstrated visco-elastic properties.     

Effect of High Hydrostatic Pressure Treatment (HHPT) on Quality and Shelf Life of Atlantic Mackerel (Scomber scombrus)

The ability of high hydrostatic pressure treatment (HHPT) to extend the shelf life of Atlantic mackerel (Scomber scombrus) was assessed in this study. For that purpose, fillets were subjected to pressure treatments at 200, 300, 400 MPa at 5, 10, 15 °C for 5 and 15 min. The influence of pressure treatments on the levels of trimethylamine nitrogen (TMA-N) and thiobarbituric acid (TBA) as well as color changes was investigated. The suitable combinations were determined as 200 MPa, 15 °C for 5 min. and 400 MPa, 5 °C for 5 min. In the second stage, the shelf life of samples, which were treated at these conditions, stored at 4?±?0.5 °C were studied by monitoring pH, color, sensorial features (appearance and odor), TMA-N, TBA, total volatile basic nitrogen, histamine, and total mesophilic aerobic count. The unpressurized mackerel samples were acceptable up to only 7 days compared to 17 and 19 days after 200 and 400 MPa treatments; respectively. The results obtained in this study showed that HHPT in combination with chilled storage can improve the shelf life and quality of fish.     

高静压加工对新鲜蛋液微生物及品质的影响

研究在不同处理压力和时间条件下,高静压对新鲜全蛋液微生物(细菌总数、大肠菌群)、色泽、乳化特性(乳化活力、乳化稳定指数)及起泡特性(起泡性、泡沫稳定性)的影响。结果表明:200 MPa处理10 min,全蛋液微生物指标已符合国家标准;相比空白组,400 MPa处理10 min,全蛋液乳化活力及乳化稳定性显著增加,300 MPa处理20 min及400 MPa处理10 min全蛋液起泡性较好,而400 MPa处理10~15 min及500 MPa处理5~15 min可使全蛋液颜色更鲜亮。综上,适当的高静压处理可使全蛋液达到有效杀菌且改善其品质的目的。     

Kinetic Study of the Combined Effect of High Hydrostatic Pressure and Temperature on the Activity of Lactobacillus delbrueckii ssp. bulgaricus Aminopeptidases

ABSTRACT:  The effect of high hydrostatic pressure (HHP) (100 to 700 MPa) combined with temperature (20 to 40 °C) on the activity of 5 aminopeptidases (PepN, PepX, PepY, PepC, and PepA) of Lactobacillus delbrueckii ssp. bulgaricus ACA-DC 0105, used as starter culture for feta cheese production, was studied. Aminopeptidases PepN, PepX, and PepA were activated at pressures up to 200 MPa, at temperatures up to 40 °C. PepY and PepC appeared to be more sensitive to pressure and temperature treatment leading to inactivation for pressures above 100 and 200 MPa, respectively, combined with temperature above 30 °C. A multi-parameter equation was used for predicting the activation of PepN, PepX, and PepA aminopeptidases in the pressure and temperature domain. Overall, processing at 200 MPa and 20 °C may be selected as the optimum conditions for maximum activation of 4 out of 5 aminopeptidases of L. delbrueckii ssp. bulgaricus. A 20-min treatment at these conditions leads to an average 3-fold increase in activity, which could lead to better and faster maturation of white cheese.     

超高压处理对鲜杏鲍菇品质的影响

本文以新鲜杏鲍菇为研究对象,研究了超高压不同处理方式下(不同压力100 MPa、150 MPa、200 MPa、250 MPa、300MPa,不同保压时间3 min、6 min、9 min、12 min、15 min、18 min),对杏鲍菇多酚氧化酶(PPO)、失重率、色差、硬度、感官等品质的影响。研究结果表明,超高压处理后杏鲍菇的PPO酶活力和弹性随着压力的升高和保压时间的延长出现先下降后上升的变化,色差的亮度(L*)值和硬度则逐渐降低,黄度(b*)值和失重率则逐渐增加。在储藏期内(0~12 d),贮藏温度为4℃,超高压处理下(压力200 MPa保压时间9 min)的酶活力低于未处理的杏鲍菇样品,而高压处理的失重率增幅大于未处理组样品,而色差和硬度变化则小于未处理组样品。通过实验分析得到杏鲍菇超高压处理的最佳压力和保压时间参数为:200 MPa、9 min。     

Comparison of Microbial Inactivation and Rheological Characteristics of Mango Pulp after High Hydrostatic Pressure Treatment and High Temperature Short Time Treatment

The effects of high hydrostatic pressure (HHP) treatments at pressures of 300–600 MPa for 1–20 min and of high-temperature, short-time (HTST) treatment on the inactivation of natural microorganisms in blanched mango pulp (BMP) and unblanched mango pulp (UBMP) were investigated. No yeasts, molds, or aerobic bacteria were detected in BMP or UBMP after HHP treatments at 300 MPa/15 min, 400 MPa/5 min, 500 MPa/2.5 min, and 600 MPa/1 min and HTST treatment at 110 °C/8.6 s. Therefore, these conditions were selected to study the effects of HHP and HTST treatments on pectin methylesterase (PME) activity, water-soluble pectin (WSP) levels, and the rheological characteristics of UBMP and BMP. HHP treatment at a pressure of 600 MPa for 1 min significantly reduced PME activity in UBMP and significantly activated PME in BMP, whereas pressures of 300–500 MPa activated PME regardless of blanching. However, PME activity was reduced by 97 % in UBMP and was completely inactivated in BMP by HTST treatment. WSP levels were significantly decreased by HHP treatment but were increased by HTST treatment in UBMP and BMP. Both HHP and HTST treatments increased the viscosity, storage modulus, and loss modulus of UBMP and BMP. No significant changes in total sugar, total soluble solids, titratable acid, or pH were found after any treatment.     

Effects of High Hydrostatic Pressure Combined with Blanching on Microorganisms and Quality Attributes of Cloudy and Clear Strawberry Juices

Effects of high hydrostatic pressure combined with blanching on microorganisms and quality attributes of strawberry juices were investigated. High hydrostatic pressure at 600 MPa/4 min/ambient temperature inactivated total aerobic bacteria, coliform bacteria, yeasts, and molds in juices, ensuring their microbiological safety. Under this condition, the cloudiness of cloudy juices increased by 54.49% and its viscosity decreased by 12.40%. Ascorbic acid decreased by 7.82% in cloudy juices and 12.60% in clear juices. The content of total volatile flavor compounds increased by 13.21% in cloudy juices and decreased by 6.92% in clear juices. No significant changes in anthocyanins, total phenols, and antioxidant capacity were found with high hydrostatic pressure treatment.     

Effects of High Hydrostatic Pressure on the Physical,Microbial, and Chemical Attributes of Oysters (Crassostrea virginica)

The change in the quality attributes (physical, microbial, and chemical) of oysters (Crassostrea virginica) after high hydrostatic pressure (HHP) treatment at 300 MPa at room temperature (RT, 25 °C) 300, 450, and 500 MPa at 0 °C for 2 min and control oysters without treatment were evaluated over 3 wk. The texture and tissue yield percentages of oysters HHP treated at 300 MPa, RT increased significantly (P < 0.05) compared to control. Aerobic and psychrotrophic bacteria in control oysters reached the spoilage point of 7 log CFU/g after 15 d. Coliform counts (log MPN/g) were low during storage with total and fecal coliforms less than 3.5 and 1.0. High pressure treated oysters at 500 MPa at 0 °C were significantly higher (P < 0.05) than oysters HHP treated at 300 MPa at 0 °C in lipid oxidation values. The highest pressure (500 MPa) treatment in this study, significantly (P < 0.05) decreased unsaturated fatty acid percentage compared to control. The glycogen content of control oysters at 3 wk was significantly higher (P < 0.05) when compared to HHP treated oysters [300 MPa, (RT); 450 MPa (0 °C); and 500 MPa (0 °C)]. HHP treatments of oysters were not significantly different in pH, percent salt extractable protein (SEP), and total lipid values compared to control. Based on our results, HHP prolongs the physical, microbial, and chemical quality of oysters.