基于质构品质变化的芒果果粒加工工艺优化

以质构品质为评价指标,研究了不同芒果品种、成熟度、硬化剂、硬化剂浓度、硬化时间、果粒大小对芒果果粒硬化效果的影响,并通过正交实验确定芒果果粒加工工艺优化参数。结果表明:台农芒果粒的硬度、咀嚼性显著高于贵妃芒、玉芒,弹性显著高于贵妃芒、玉芒、金煌芒。青熟、完熟芒果果粒硬度显著高于过熟芒果。乳酸钙处理组的芒果果粒硬度显著高于氯化钙、海藻酸钠处理组。正交实验结果表明,以完熟台农芒为原料,以乳酸钙为硬化剂,影响果粒硬度的主要因素是果粒大小与硬化剂浓度,适宜芒果果粒加工的优化工艺为:果粒大小为1.5 cm×1.5 cm×1.5 cm,硬化剂浓度为0.04 g/mL,硬化时间为2 h。在该条件下,芒果果粒的硬度为525.17 g。     

芒果片真空预处理联合超声辅助渗透脱水的传质动力学及品质分析

为解决芒果果脯生产过程中传质效率低、加工时间长的问题,该文研究了脉冲真空预处理联合超声辅助渗透脱水对芒果传质动力学、质量特性和微观结构的影响。结果表明：脉冲真空预处理联合超声辅助渗透脱水组的芒果失水率（54.43%）最高,较常规渗透脱水、脉冲真空预处理渗透脱水、超声辅助渗透脱水组分别高45.85%、14.06%、29.38%,增固率（12.81%）较常规渗透脱水、超声辅助渗透脱水、脉冲真空预处理渗透脱水组分别高90.03%、53.43%、32.06%。用Azuara模型拟合渗透脱水过程中失水率和增固率的变化,高回归系数（R2>0.97）和低RMSE表明Azuara模型可以较好拟合芒果渗透脱水过程,预测脉冲真空预处理联合超声辅助渗透脱水组的平衡脱水率、增固率最高,分别为65.06%和23.35%。测定色泽和质构,发现超声辅助渗透脱水组、脉冲真空预处理联合超声辅助渗透脱水组芒果硬度值显著低于常规渗透脱水组和脉冲真空预处理渗透脱水组（p<0.05）,而芒果色泽得到了较好保护。通过扫描电镜的观察,发现超声处理使芒果细胞壁塌陷与变形、细胞横截面积变小、微孔增多。此外,真空对芒果硬度和微观结构的影响均较小。综上,脉冲真空预处理联合超声辅助渗透脱水通过改变芒果细胞结构、增加传质微通道,提高了渗透脱水的效率,缩短加工时间,可以较好保护芒果色泽,但会导致硬度的下降。     

果胶酯酶在果粒生产中的应用

果胶酯酶作为一种新型的加工助剂,能最大程度地提高成型果粒的含量,有助于保持每一个果粒原有的形状和硬度,易于进一步的加工处理.     

超高压对鲜切胡萝卜硬度的影响及机制研究

鲜切果蔬的品质在加工后易受到破坏,超高压技术(high pressure processing,HPP)在鲜切果蔬品质保持方面具潜力。旨在探究鲜切果蔬的硬度随压力变化的规律及硬度变化的机制。本文以胡萝卜为对象,研究了超高压(100~600 MPa,5 min)对鲜切胡萝卜硬度、细胞膜完整性、果胶甲酯酶(pectin methylesterase,PME)及细胞壁果胶组成的影响。100 MPa处理后胡萝卜硬度无显著变化,随着压力增加,胡萝卜相对电导率显著增加,硬度显著下降,当达到300 MPa后,尽管压力继续升高,相对电导率和硬度变化已不显著;同时,高压处理后碱溶性果胶(sodium carbonate soluble pectin,NSP)增加,水溶性果胶(water soluble pectin,WSP)下降,但高压不能充分钝化果胶甲酯酶。超高压处理后细胞膜透性的改变和细胞壁果胶组分的变化共同影响了鲜切胡萝卜的硬度。     

超高压升压和贮藏期胡萝卜软化特征及其机制

目的:明确升压阶段及超高压处理后贮藏期内果蔬质构的动态变化规律。方法:本文研究100～600 MPa、0～2 min高压处理对胡萝卜硬度的影响,并探究其在14 d贮藏期内的硬度变化。从细胞膜透性、细胞显微结构、细胞壁果胶的酶促降解与组分变化,探究硬度变化的机理。结果:压力大于200 MPa会引起胡萝卜硬度下降(P0.05),300 MPa时硬度仅剩37.7%。保压阶段和贮藏过程中硬度变化不明显。相对电导率随压力的升高而增加,表明细胞膜透性增加。用透射电镜观察胡萝卜的微观结构,结果表明,高压处理能引起细胞形变,400 MPa导致膜裂解,600 MPa导致部分细胞溃散。超高压处理后胡萝卜在4℃贮藏期内,细胞分离和细胞壁降解程度加深。果胶甲酯酶、聚半乳糖醛酸酶仍保持较高活性,水溶性果胶含量显著下降(P0.05),向螯合性、碱溶性果胶的转化加速。结论:超高压引起的胡萝卜硬度损失主要由高压对细胞膜的机械损伤引起,果胶组分的转化有利于贮藏期内硬度的保持。     

果胶甲酯酶对保持苹果质构作用的研究

从质构、酯化度、水溶性果胶含量三个方面研究了果胶甲酯酶对苹果块质构的保持作用。实验证明,用果胶甲酯酶能有效地保持苹果的质构。由经果胶甲酯酶处理的苹果切块(酶浓度0.4mL／50g水,Ca2 浓度0.2％,pH4.5,在0.09MPa下脱气20s)制成的悬浮饮料,在37℃、RH为50％的环境下放置30d后,其硬度保持率为48.5％,咀嚼度保持率为33.46％;未经该酶处理的样品的相应指标分别为32.5％和16.45％。同时模拟实验也表明,苹果中果胶的酯化度从78.6％下降到48.7％,果胶物质在介质中的溶出率从38.95％下降到15.59％。     

响应面分析法优化干椰纤果制备工艺

通过单因素及响应面试验探讨羧甲基纤维素钠(CMC)真空渗透条件和热风干燥条件对椰纤果的复水性、复水后的质构等的影响。结果表明：采用CMC真空渗透处理可以改善干椰纤果的复水比、复水后的硬度和弹性。影响干椰纤果复水性质的因素主要是CMC质量分数、固液比、干燥温度、真空渗透时间,干椰纤果制备的最佳工艺条件为：CMC质量分数0.90%、固液比1:2、真空渗透时间4.5h、干燥温度60℃。     

超高压对鲜切猕猴桃果片多聚半乳糖醛酸酶及品质的影响

采用超高压处理对鲜切猕猴桃片进行保鲜,研究了超高压处理对贮藏期间多聚半乳糖醛酸酶活性、果片硬度、可溶性果胶和VC含量的影响。研究结果表明:猕猴桃片采用600MPa压力、30℃下加压10min后,在4℃条件下贮藏9d,与未超高压处理的对照组相比,超高压处理的鲜切猕猴桃片多聚半乳糖醛酸酶活性较低,果片硬度、可溶性果胶含量、VC含量和可溶性果胶变化不显著;600MPa超高压处理可通过抑制多聚半乳糖醛酸酶活性而维持果片硬度,同时可有效控制VC的损失。     

超高压与重组果胶甲酯酶抑制剂联合应用对鲜榨橙汁果胶甲酯酶活性及品质的影响

为了探究超高压与重组果胶甲酯酶抑制剂(recombinant pectin methylesterase inhibitor,rPMEI)联合处理对鲜榨橙汁中果胶甲酯酶(pectin methylesterase,PME)活性及品质的影响,研究了超高压(400、500和600 MPa,5 min,20 ℃)与重组果胶甲酯酶抑制剂对橙汁微生物、PME酶活、色泽和V_C含量的影响。结果表明:超高压处理条件为500 MPa/5 min,rPMEI添加浓度为0.06 mg/mL时,橙汁中的菌落总数、霉菌与酵母菌数均能达到农业行业标准《NY/T 434-2016绿色食品、果蔬汁饮料》所规定的要求,同时PME被完全钝化;橙汁色泽变化显著小于热处理组(ΔE*=1.22<2.26);V_C保留率为85.1%,显著高于热处理组(保留率=8.33%)。     

超高压处理对鲜切马铃薯质地及细胞壁多糖含量的影响

本文旨在探究鲜切马铃薯的质地随压力变化的规律及质地改变的机制。研究了超高压(HPP,100~600 MPa,10 min)对鲜切马铃薯色泽、硬度、咀嚼度、细胞壁相关酶活及多糖组成的影响。结果表明,HPP在压力≥ 500 MPa下对鲜切马铃薯的褐变抑制较好,300 MPa时褐变严重且程度高于空白。HPP相较传统热处理,能够更好的保持鲜切马铃薯的硬度及咀嚼度;但相比空白,HPP处理后硬度均有不同程度的下降,其中300 MPa时硬度下降最大,达到500 MPa时,硬度出现回升,咀嚼度在该压力下同样存在回升现象。HPP在一定程度上改变了马铃薯细胞壁相关酶活性及多糖含量,果胶甲酯酶(PME)活性在压力≤ 500 MPa具有稳定性,同时HPP可抑制多聚半乳糖醛酸酶(PG)和内切β-葡聚糖酶(Cx)活性,在压力100、500、600 MPa下提高β-葡糖苷酶及外切β-葡聚糖酶(C₁)活性;相比空白,HPP处理后鲜切马铃薯纤维素(CEL)、碱溶性果胶(NSF)、螯合性果胶(CSF)含量显著(P<0.05)提高,其中CSF含量在300 MPa下显著(P<0.05)低于空白水平,水溶性果胶(WSF)含量在100、600 MPa下显著(P<0.05)下降,其余压力下无显著变化,而经HPP处理后鲜切马铃薯半纤维素(HC)含量均显著(P<0.05)下降。经相关性分析,HPP处理后马铃薯硬度、咀嚼度与CSF、NSF、CEL含量呈显著或极显著正相关(P<0.05或P<0.01),与WSF含量呈极显著(P<0.01)负相关,与HC含量相关性不显著,PME活性对其质构指标影响较大。综上,超高压处理后细胞壁多糖组成及含量变化影响了鲜切马铃薯的质地。     

Texture improvement of fresh and frozen mangoes with pectin methylesterase and calcium infusion

BACKGROUND: A major problem of mango products is texture loss. The effect of commercial pectin methylesterase (PME) and calcium infusion on improvement of the texture of both fresh and frozen‐thawed mango cubes was investigated in the present study. RESULTS: The weight gain and moisture content of mango samples were greater at relatively high vacuum level (10 kPa). The PME activity of samples infused with PME and calcium at 10 kPa increased fourfold in comparison with that of control and water‐infused samples. The combined effect of PME and calcium was found to improve the texture and microstructure of both fresh and frozen‐thawed mangoes. Fresh mangoes infused with PME and calcium at 10 kPa showed significantly higher firmness than control fresh samples. Frozen‐thawed mangoes infused with PME and calcium at 50 kPa and atmospheric pressure had superior texture and microstructure in comparison with control frozen‐thawed samples. CONCLUSION: The results of the present analysis allow for a better appreciation of the role of PME, calcium and appropriate infusion conditions in improving the texture of both fresh and frozen‐thawed mangoes. Copyright © 2012 Society of Chemical Industry     

Effect of Pectinmethylesterase Infusion Methods and Processing Techniques on Strawberry Firmness

Strawberry halves were pretreated with fungal pectinmethylesterase (PME) and calcium chloride using, respectively, passive osmotic infusion, vacuum‐assisted infusion, and pressure‐assisted infusion with the aim to improve the firmness. The vacuum‐assisted procedure was observed to be the only method able to accomplish an uptake of infusion solution and hence capable of improving the firmness of the strawberries. Significantly less firmness increase was realized when tomato PME was vacuum‐infused instead of fungal PME. Strawberry halves were pretreated by vacuum‐assisted infusion with fungal PME and calcium chloride and were subsequently subjected to thermal treatments at 60 °C and 80 °C and pressure treatments at about 400 MPa and 550 MPa. For all treatments studied, the pretreated sample was significantly firmer compared with the reference sample. For the thermal processes, the residual firmness relative to the initial value before treatment was depending on the temperature of the treatment and not on the pretreatment. However, vacuum‐assisted infusion of PME and calcium could limit the portion of firmness loss due to pressure treatment to 30% compared with 80% for non‐pretreated fruits.     

MICROWAVE-VAPOR HEAT DISINFESTATION ON ORIENTAL FRUIT FLY EGGS IN MANGOES

The objective of this research was to develop a microwave‐vapor heat treatment (MW‐VHT) for mangoes (Mangifera indica L.) cv. Namdokmai Si Thong to disinfest the oriental fruit fly, Bactrocera dorsalis (Hendel). The mortality of oriental fruit fly eggs and quality acceptability characterized by thermal‐death‐time and thermal‐quality‐time overlay plots were initially obtained by hot‐water immersion. Two treatments within a range of acceptable quality were selected for inoculation experiments to confirm MW‐VHT process. The acceptable range was temperature ranging from 46 to 55C with time ranging from 2 to 20 min. The MW‐VHT using microwave for preheating followed by vapor for holding processes effectively disinfested oriental fruit fly eggs. Changes in physiochemical properties of mangoes, e.g., color, titratable acid (TA), total soluble solid (TSS), TSS/TA and firmness, of MW‐VHT‐treated mangoes were not significantly different (P > 0.05) from physiochemical properties of the nontreated mangoes. MW‐VHT resulted in less heat damage of mangoes than conventional vapor heat treatment (VHT) and shortened process time more than 90% during the preheating period. MW‐VHT also retained equivalent or better lethality of oriental fruit fly eggs than did conventional VHT.     

Enzyme infusion prior to thermal/high pressure processing of strawberries: Mechanistic insight into firmness evolution

Strawberries were infused with fungal pectinmethylesterase (PME) and calcium chloride, followed by a thermal (70 °C–0.1 MPa), a high pressure (25 °C–550 MPa) or a combined thermal-high pressure (70 °C–550 MPa) process. Macroscopic (firmness) and microscopic characteristics were assessed to evaluate the texture of the fruits. In order to interpret the texture changes, the chemical structure of pectin was investigated. Processing of strawberries caused a decrease in firmness, which was limited by infusion of PME and calcium chloride, although the extent of beneficial effects depended on the type of processing. PME was able to decrease the degree of methoxylation of pectin, which was accompanied by an increased crosslinking of the chains. During high pressure or combined thermal-high pressure processing, the degree of methoxylation of pectin in infused strawberries was even further decreased, probably due to a higher activity of the fungal PME under high pressure. In case of the high pressure process, this was reflected in a very firm texture. However, the combined thermal-high pressure process caused more severe tissue damage, in spite of the advantageous pectin properties.Industrial relevanceDuring high pressure processing of strawberries many nutritional and sensorial characteristics are quite well preserved. Unfortunately, texture of strawberries deteriorates during such processes. This paper provides mechanistic insight into how infusion of fungal pectinmethylesterase and calcium ions in strawberries can preserve the firmness of these fruits during high pressure processing.     

High-pressure treatment of cloudy apple juice

A factorial design with four factors (pressure, holding time, temperature and waiting period between crushing of apple and high-pressure (HP) treatment) was built up to study the effect of HP treatment on pectin methylesterase activity (PME, EC 3.1.1.11) in cloudy apple juice. PME activity was measured by the methanol release during the storage of samples at 4 °C for 1 month. Only the holding time of the treatment and three interactions between factors (holding time×temperature, pressure×waiting and holding time×waiting) had significant effects on the PME level. Increasing the pressure or the holding time at moderate temperatures (15-40 °C) increased the activity. PME purified from apple was pressure stable in the range 100-600 MPa at 25 °C. The soluble pectin content was not changed after HP treatment. The particles size increased with the temperature reached during the treatment, in agreement with a diffusion-limited-aggregation model but were independent of pressure and holding time. In a separate experiment we found a positive correlation between the PME activity and the residual content of the catechins suggesting that polyphenoloxidase (PPO, EC 1.14.18.1) and oxidized polyphenols play a role in the PME activity level after HP treatment.     

高压均质对NFC水蜜桃浊汁稳定性及品质的影响

本文采用高压均质技术,探究了均质压力（20~40 MPa）及次数（1~2次）对NFC水蜜桃浊汁的混浊度、离心沉淀率、粒径、Zeta电位等稳定性指标和pH、TSS、总酸、固酸比、还原糖、色泽、总酚、V_C等品质指标的影响。结果表明:高压均质（30~40 MPa/1、20~40 MPa/2）可有效提高NFC水蜜桃浊汁的稳定性,离心沉淀率较未处理组下降13.49%~24.22%,平均颗粒粒径由1853.67 nm降至501.10~665.27 nm,绝对Zeta电位值显著提高（P<0.05）。随着均质压力及次数的增加,浊汁中可溶性果胶含量上升,而残存果胶甲基酯酶活力逐渐降低。高压均质后,浊汁色泽显著改善,L*值升高,褐变指数BI值下降（P<0.05）;30 MPa/1下,品质保持最佳,总酚、V_C含量较未处理组显著提高（P<0.05）,而pH、TSS、总酸和固酸比无变化（P>0.05）;随着均质次数增加,pH、TSS、总酚和V_C含量显著降低（P<0.05）,品质下降。高压均质处理可有效提高NFC水蜜桃浊汁稳定性、抑制褐变,并提高总酚、V_C等营养物质含量。     

Vacuum Infusion of Citrus Pectinmethylesterase and Calcium Effects on Firmness of Peaches

Vacuum infiltration of Majestic peaches (Prunus persica) for 1 hr with a solution of Marsh grapefruit pectinmethylesterase (PME) containing 100 mg/L CaCl₂ significantly increased firmness of canned peaches. Mean firmness of peaches infused 2 hr and thermally processed was 13.9 J/Kg as compared to 3.2 J/kg for noninfused, processed controls. The calcium content increased from 278 to 432 mg/kg during 2 hr infusion of blanched peaches. Specific activity of PME in peach halves increased more than 20 fold after infusion.     

Effect of Osmotic Dehydration Under High Hydrostatic Pressure on Microstructure, Functional Properties and Bioactive Compounds of Strawberry (Fragaria Vesca)

Sliced strawberries were subjected to combined osmotic dehydration (40 °Brix) and high hydrostatic pressure (HHP) at 100, 200, 300, 400 and 500 MPa for 10 min. This research was carried out to study the effects of pressure on firmness, polysaccharides, total dietary fibre and microstructure, functional properties (rehydration ratio and water holding capacity) and bioactive compounds (anthocyanins, flavonoid and total phenolic). HHP affected the texture of the fruits leading to soft fruits due to increasing pressure. Fruit microstructure evidenced influence of pressure presenting the pressurised samples irregular matrices compared to samples treated at 0.1 MPa (control samples). Polysaccharides increased with pressure. Total dietary fibre, anthocyanins, flavonoids and total phenolic content showed a decrease with pressure when compared to control samples. Based on results, minor alterations of the mentioned quality parameters were evidenced when working in the range of 300–500 MPa.     

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。     

超高压处理对LDPE、PA6食品包装材料包装性能可逆性的研究

本文在不同条件下对LDPE、PA6进行超高压(HPP)处理,测定不同压力、保压时间及存储时间对材料拉伸强度、热封性能、阻隔性能、热性能以及包装性能可逆性的影响。实验表明:处理压力、保压时间及存储时间对2种材料的热封性均未产生显著影响,但LDPE、PA6试样的拉伸强度随压力升高明显增大;当压力300 MPa时LDPE的透湿性逐渐上升,当压力300 MPa时LDPE的透湿性又逐渐降低,对PA6来说,当压力100 MPa时,材料的透湿性明显下降由10.13 g/(m2·d)(0.1 MPa/10 min)降低到6.79 g/(m2·d)(200 MPa/10 min),但随压力增大透湿性下降的幅度并不明显;两种材料的熔融焓在HPP下均有升高,当存储24 h后,两种材料的ΔH又有所恢复;与0.1 MPa下相比,经过HPP后对异丙基甲苯在LDPE(500 MPa)和PA6(100 MPa)薄膜中的渗透率分别降低约50%和58%,但随着存储时间的延长又逐渐恢复至常压下的渗透率。研究发现实验中采用的LDPE和PA6 2种薄膜的包装性能均有可逆现象出现。