Colour degradation and rheology of green chilli puree during thermal processing

The kinetics of degradation of both green- and total-colour of green chilli puree was studied at selected temperatures (50–90 °C). A fractional conversion concept was applied to determine the kinetic parameters. The degradation of green- and total-colour followed first order reaction kinetics. In the case of green colour the data was based on changes in Hunter – a value while L  ×  a  ×  b was found to adequately represent total colour change. Dependence of the rate constant during heat treatment obeyed the Arrhenius relationship. The activation energy values for green- and total-colour degradation were 23.04 and 25.02 kJ mol^–1, respectively. These results indicated that total colour should be used as the quality indicator during thermal processing of green chilli puree. The pungency of green chilli puree decreased during thermal processing as the capsaicin content was reduced from 559 to 441 μg g^–1 while the Scoville heat unit decreased from 8500 to 7480. The puree behaved as a shear-thinning fluid and the flow activation energy at 100 r.p.m. equalled 19.22 kJ mol^–1.     

Effect of blanching on thermal color degradation kinetics and rheological behavior of rocket (Eruca sativa) puree

Rheological behavior and green color retention are important parameters during thermal processing of pureed leafy vegetables. In this study, an attempt was made to investigate thermal effect on the color and rheological characteristics of rocket (Eruca sativa L.) purees made from leaves with and without stems. The color degradation kinetics of rocket puree was studied at temperatures between 60 and 110 °C using fractional conversion technique. The degradation kinetics of puree followed a 1st order reaction kinetics and the activation energy values for puree with and without stems were ranged between 38.90 and 51.21 kJ/mol. Effects of blanching on oscillatory and steady flow rheology of puree made from leaves with and without stems were studied in the temperature range of 25 to 70 °C. All puree samples exhibited an elastic modulus that is larger than the loss modulus in the tested frequency range. Blanched leaf puree exhibited the highest mechanical strength at 70 °C. The steady flow data fitted the Herschel–Bulkley model well. The complex viscosity and the apparent viscosity at similar frequency and shear rate range failed to follow the Cox–Merz rule. Scanning electron microscopy and sieve-analysis revealed that the leaf puree had smaller particle sizes than puree with stems.     

热处理方式对菠萝果浆理化品质的影响研究

用高压蒸煮、沸水浴与微波加热的方式处理菠萝果浆,研究处理后果浆的理化品质,分析三种方式的影响,并考察贮藏2周后果浆的理化指标的变化。结果表明:热处理能延长菠萝果浆的保质期。三种方式对果浆pH、可溶性固形物和总酸含量这三项指标影响不大,均使得总糖成分有所上升;高压蒸煮对浊度影响较大;微波处理的VC损耗小于其他两种方式;高压处理使果浆产生的色差最大,其次是沸水处理的,而微波处理有利于菠萝果浆颜色的保持。      

热处理方式对菠萝果浆理化品质的影响研究

用高压蒸煮、沸水浴与微波加热的方式处理菠萝果浆,研究处理后果浆的理化品质,分析三种方式的影响,并考察贮藏2周后果浆的理化指标的变化.结果表明:热处理能延长菠萝果浆的保质期三种方式对果浆pH、可溶性固形物和总酸含量这三项指标影响不大,均使得总糖成分有所上升;高压蒸煮对浊度影响较大;微波处理的Vc损耗小于其他两种方式;高压处理使果浆产生的色差最大,其次是沸水处理的,而微波处理有利于菠萝果浆颜色的保持.     

超高压与热处理对芒果果浆抗氧化成分及抗氧化能力的影响

探讨不同加工处理对芒果果浆在贮藏过程中抗氧化成分和抗氧化能力的影响规律,以期为芒果果浆的贮藏提供指导。对芒果果浆分别进行超高压（600MPa,1min）、高温短时（110℃,10s）和低温长时处理（70℃,30min）,分析不同加工处理后芒果果浆在贮藏过程（0¹5W）中抗氧化成分（L-抗坏血酸、总酚和总类胡萝卜素）和抗氧化能力（采用DPPH和FRAP法评价）变化。结果表明:不同加工处理对芒果果浆在贮藏过程中其抗氧化成分和清除DPPH·能力有显著影响,其中超高压处理能够较好的保持芒果果浆的总酚和总类胡萝卜素含量以及样品清除DPPH·能力;用零级、一级和零级、一级联合动力学模型拟合各抗氧化成分指标的动态变化的研究发现,联合动力学模型可以更好地表示L-抗坏血酸、总酚和总类胡萝卜素的动态变化（R>0.988）。本研究对不同加工处理后芒果果浆在贮藏过程中抗氧化成分和抗氧化能力变化进行了分析,现有的分析将为超高压技术应用于工业化生产芒果果浆中贮藏性、稳定性和质量评价提供数据支撑。      

Color degradation kinetics of pineapple puree during thermal processing

Improvement of color, as a quality attribute of processed pineapple puree, has been made possible by the increase in knowledge of kinetic of color change. The kinetics of color degradation of pineapple puree were investigated during heat treatment at 70-110 °C in order to cover the temperature range that used in preheat and sterilization of commercial aseptic pineapple puree. Color changes associated with heat-treated puree were monitored using Hunter colorimeter (L, a, b, total color difference—ΔE) and Browning index (A₄₂₀). The changes in L and b values fitted well to the first-order kinetic model while ΔE, a value, and Browning index followed the zero-order kinetic. The dependence of the rate constant on temperature was represented by an Arrhenius equation. The results suggested that ΔE and lightness, based on activation energy, were the most sensitive measures of color change at temperature range 70-90 and 95-110 °C, respectively.     

热烫条件对香蕉浆褐变的影响

研究了热烫温度、热烫时间、热烫固液比以及热烫液加酸量对香蕉热处理过程中PPO酶活以及香蕉浆褐变的影响。结果表明,香蕉热处理的优化条件为:热烫温度为100℃、热烫时间为6min、热烫固液比为1∶5(w∶v)和柠檬酸浓度为0.6%。在此条件下进行验证实验,测得香蕉浆中的残留PPO酶活为16U,香蕉浆液的褐变度仅0.072,对控制香蕉在加工过程中的褐变有明显效果。      

Effect of blanching on mineral and oxalate content of spinach

Summary. Unblanched and blanched spinach were sampled from a factory line with conventional water blanchers. the samples were analysed for potassium, sodium, calcium, magnesium, phosphorus, nitrate and soluble and insoluble oxalate. the main results show that spinach takes up calcium from the water during blanching. This increase in calcium content of the spinach has a direct influence on the ratio between the soluble and insoluble form of oxalate. Loss of nitrate is higher than that of the other water soluble constituents.
In a small trial, an attempt was made to increase the nutritional value of spinach by precipitation of all soluble oxalate through addition of excess of calcium chloride to processed, chopped spinach. However, a taste panel rated the enriched sample as inferior owing to its colour. A small blanching trial with tap, distilled and softened water showed that the amount of calcium in tap water has no such undesirable effect on colour.     

Effect of mild pressure treatments and thermal blanching on yellow bell peppers (Capsicum annuum L.)

The effect of thermal blanching, in conditions carried out at industrial level, and pressure treatments of 100 and 200 MPa on quality of yellow bell peppers was compared. While the soluble protein content was reduced from 13 to 34% by the blanching treatments, the pressure treated peppers showed equal (100 MPa) to higher levels (up to 33%) for 200 MPa. The ascorbic acid (AA) content of the peppers was not affected by thermal blanching, with the exception of the more severe condition (98 °C/150 s), whereas all pressurized samples showed an increase of AA content in the range of 11-48%. Polyphenol oxidase activity was found mainly in the soluble fraction (around 80%) and decreased progressively as the temperature and time of blanching increased, till reaching about 50% the value of unprocessed peppers, while the pressure treatments showed no effect. Peroxidase activity was practically absent in the ionically-bound fraction (only 1% of total activity) and was reduced by the blanching treatments by 80%-100%, while the pressure treatments only reduced peroxidase activity from 5 to 10%. Activity of pectin methylesterase was undetectable in fresh and both thermally and pressure processed peppers. Firmness of peppers measured from the skin side was about 2.5 fold higher than from the flesh side. After the thermal blanching and the pressure treatments, firmness of peppers was better retained when measured from the flesh side. Upon freezing the pressure treated and the thermally blanched peppers showed similar relative decreases in firmness.     

不同蔬菜热烫对维生素C的影响

对黄瓜、菠菜、藕、蒜苔四种新鲜脆性蔬菜在不同温度、时间下进行热烫,运用2,6-二氯靛酚法测定其中的维生素C含量。结果表明:在70～100℃内,热烫温度越低,所需时间越长,而维生素C的损失越高;热烫温度升高,热烫时间缩短,维生素C损失降低;当热烫温度过高时,维生素C的损失增加。大多数蔬菜热烫的温度为90℃,时间为40～60s时,维生素C的保存率最高。      

杀青条件对杜仲茶主成分的影响

探讨了杀青条件对杜仲茶主成分的影响,结果表明:(1)杜仲鲜叶不切,直接采用复干机杀青有利于杜仲茶主成分的保留:(2)杀青条件以杀青温度125℃、杀青叶量0.30kg、杀青时间3min最有利于杜仲茶主成分的保留。     

超高压处理对椰肉原浆保鲜的影响

为了研究适宜的椰肉原浆的保藏方法,将椰肉原浆经过600MPa压力,保压时间10min,保压温度30℃条件下处理后在0～5℃条件下贮藏16d,分析超高压处理对贮藏期间椰肉原浆的菌落总数、色泽、pH、电导率影响.结果表明:与对照组相比,超高压处理后可以明显抑制微生物的生长.L、a、b值、电导率有所下降,pH升高,但在储藏期间其变化比较缓慢,在一定程度上延缓了椰肉的品质改变.所以超高压技术是一种较好的椰肉原浆保鲜的方法.     

真空烫漂处理对牡蛎肉腥味成分的影响

以感官评定为指标,采用热烫和真空脱腥相结合的方法对香港牡蛎肉进行脱腥实验,应用顶空-固相萃取和气质联用技术对脱腥前后牡蛎肉中的挥发性成分组成、含量进行分析。结果显示,在温度为80℃,时间为3min,真空度为0.07MPa的条件下进行脱腥处理,牡蛎肉中的腥味物质总数由脱腥前的12种降至10种,相对含量由19.18%降至15.19%,腥味脱除率达到了20.8%,能够较好的达到脱除牡蛎肉腥味的目的,同时呋喃类物质的增加能够提升牡蛎的肉香味。研究表明,采用热烫及真空的方法对牡蛎肉进行脱腥,能够降低牡蛎肉中的腥味成分,是一种较为有效的腥味脱除方法。      

超高压处理对椰肉原浆保鲜的影响

为了研究适宜的椰肉原浆的保藏方法,将椰肉原浆经过600MPa压力,保压时间10min,保压温度30℃条件下处理后在0～5℃条件下贮藏16d,分析超高压处理对贮藏期间椰肉原浆的菌落总数、色泽、pH、电导率影响。结果表明:与对照组相比,超高压处理后可以明显抑制微生物的生长。L、a、b值、电导率有所下降,pH升高,但在储藏期间其变化比较缓慢,在一定程度上延缓了椰肉的品质改变。所以超高压技术是一种较好的椰肉原浆保鲜的方法。      

The preservation and storage of leaf protein preparations

Moist leaf protein is most readily preserved for a few months by adding 1 % acetic acid. When dried leaf protein is stored, there is oxidation of the lipid fraction which decreases the carotenoid and tocopherol contents, and affects the nutritional value and palatability of the protein. Oxidation is especially rapid when products are stored in the light because of the catalytic effect of chlorophyll. The preparations contain 0.8 to 1.7 mg/g of β-carotene that oxidises fast giving some protection to other lipids. Using carotene oxidation as an index, satisfactory storage is best achieved by processing extracts rapidly to avoid the destruction of natural antioxidants and the formation of lipoperoxides in the juice; dried products will then keep well at room temperature, packed tightly in bags impermeable to light and oxygen.     

Effect of ultrasonic treatment on enzyme activity and bioactives of strawberry puree

The aim of this study was to evaluate the impact of ultrasound (US) at different frequencies (20, 370, and 583 kHz) and power levels (35 and 48 W) on the residual activity (RA) of peroxidase (POD) and polyphenol oxidase (PPO) in strawberry puree. Total anthocyanin content (TAC), total phenolic content (TPC), ferric ion reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) were also assessed. Results were compared with untreated, thermally treated at 40 °C (control) and pasteurized (90 °C) strawberry puree. POD and PPO RA were significantly (P < 0.05) reduced, whilst there was a significant (P < 0.05) increase in TAC (5%–19%) in all US-treated samples in comparison with the untreated samples and the controls. US at 20 kHz (35 W) increased significantly (P < 0.05) TPC (9%) and FRAP (6%) in strawberry puree, whereas the effect of 583 kHz (48 W) on these parameters was insignificant (P > 0.05). Pasteurization inactivated POD and PPO, however, decreased dramatically TAC (14%), TPC (17%) and FRAP (9.5%) in strawberry puree. These findings suggest that US is a promising novel non-thermal food technology that can be tailored to improve the quality of strawberry puree by inactivating enzymes responsible for food deterioration whilst maintaining the content of bioactive compounds.     

不同热烫条件对胡萝卜榨汁效果的影响

通过试验了获得了热水、柠檬酸、醋酸、混合酸，蒸汽和微波6种热烫方式对胡萝卜榨汁效果影响的数据处理。其中榨汁效果主要从出汁率，可溶性固形物，pH值，颜色及稳定性5个方面进行评价。     

贮藏温度对草莓浆理化成分和品质变化的影响

探明贮藏条件对草莓浆理化成分和品质的影响。研究了常温(25℃)、0、4、-18℃冷冻贮藏期间草莓浆花色苷、V_C、可滴定酸、可溶性固形物、风味的变化。结果表明,贮藏60 d,常温和4℃冷藏草莓浆花色苷保留率为12.56%和70.6%,0℃和-18℃冷冻贮藏草莓浆花色苷保留率仍在88%以上,常温和4℃贮藏V_C保留率分别为42.26%和73.21%,0℃和冷冻贮藏V_C保留率均为90%以上;可滴定酸和可溶性固形物在0℃和冷冻贮藏60 d内无显著变化;0℃和冷冻贮藏草莓浆的色泽明显优于常温贮藏;-18℃冷冻贮藏可以较好的保持草莓浆的酸味、甜味等味觉感官品质。经综合评价,0℃和-18℃冷冻环境条件有利于草莓果浆品质的保持,可显著延缓花色苷和V_C的降解,是较合适的草莓浆保藏温度,为草莓浆加工与保藏提供了参考。