高压二氧化碳对鲜榨梨汁杀菌效果及动力学研究

本文研究了高压二氧化碳(HPCD)对梨汁中细菌菌落总数的影响,并分析其杀菌动力学。结果表明:随着温度、压强升高以及处理时间延长,梨汁中细菌菌落总数显著降低(p<0.05);在相同温度和处理时间条件下,HPCD处理显著高于热处理的杀菌效果,处理温度对HPCD杀菌具有协同效应;当HPCD处理条件为30MPa、40℃、60min时,灭菌效果最佳,梨汁中细菌菌落总数的残存率降低了2.66个对数;Weibull模型能较好地拟合HPCD处理后梨汁中细菌菌落总数的失活曲线,模型动力学参数比例因子a和形状因子b随压力增加和温度升高呈现逐渐变小的规律性变化。      

Controlled‐atmosphere storage of tomato fruit: low oxygen or elevated carbon dioxide levels alter galactosidase activity and inhibit exogenous ethylene action

The effects of 3% O₂ and 20% CO₂, both alone and together with 100 µg g⁻¹ C₂H₄, on ethylene production, chlorophyll degradation, carotenoid biosynthesis and α‐ and β‐galactosidase activity in breaker tomato (Lycopersicon esculentum Mill) fruit were investigated. The low O₂ and high CO₂ atmospheres prevented the rise in ethylene production, total carotenoid and lycopene biosynthesis and α‐ and β‐galactosidase activity and slowed down chlorophyll degradation and loss of firmness (P < 0.05). These suppressive effects were not reversed, or only in part – in the case of chlorophyll breakdown – by addition of 100 µg g⁻¹ C₂H₄ to said controlled atmospheres. After transfer from the various atmospheres to air, flesh firmness decreased and ethylene production, total carotenoids, lycopene and β‐galactosidase II activity increased but these parameters were, in all cases, still significantly different from those of fruit held in air. Keeping tomatoes in controlled atmospheres, even in the presence of ethylene, had marked residual effects. Results suggest an antagonism between elevated CO₂/low O₂ and exogenous ethylene which could determine most of the ripening parameter behaviour under controlled‐atmosphere storage, though a direct regulatory mechanism by O₂ and/or CO₂ should not be discarded. © 1999 Society of Chemical Industry     

Solubility measurement of methyl anthranilate in supercritical carbon dioxide using dynamic and static equilibrium systems

The solubility of methyl anthranilate in supercritical carbon dioxide was determined using dynamic and static equilibrium systems. Three temperatures (40, 60 and 80 °C) and a pressure range between 160 and 340 atm were applied for the dynamic solubility measurements. The flow rate was maintained at 0.5 mL min^?1 in the dynamic solubility measurements, where the solute solubility was claimed to be independent of the flow‐rate factor. Two temperatures (40 and 60 °C) and the pressure range between 100 and 265 atm were used in the static equilibrium system. The crossover pressure region was observed between 220 and 240 atm in the static system, but was not seen in the dynamic system. The solubility of methyl anthranilate determined by the static system was consistently higher than the dynamic solubility measurement, indicating that the static technique provided more reliable solubility data for methyl anthranilate than the dynamic technique. The solubility data obtained with the static system were in good agreement with the predictive models based on the Chrastil equation and the Peng–Robinson equation of state with the Panagiotopoulos and Reid mixing rule. Copyright © 2006 Society of Chemical Industry     

Simultaneous measurement of total acid content and soluble salt-free solids content in Chinese vinegar using near-infrared spectroscopy

Total acid content (TAC) and soluble salt-free solids content (SSFSC) in Chinese vinegar are 2 important indicators in the assessment of its quality. This paper shows the feasibility to determine TAC and SSFSC in Chinese vinegar by near-infrared (NIR) spectroscopy. Synergy interval partial least square (Si-PLS) algorithm was performed to calibrate the regression model. The number of PLS factors and the number of intervals were optimized simultaneously by cross-validation. The performance of the model was evaluated according to root mean square error of prediction (RMSEP) and correlation coefficient (R) in the prediction set. The optimum Si-PLS model for TAC was achieved with RMSEP = 0.264 g/100 mL and R(p) = 0.9655; the optimum Si-PLS model for SSFSC was achieved with RMSEP = 1.93 g/100 mL and R(p) = 0.9302. The overall results demonstrated that NIR spectroscopy combined with Si-PLS could be utilized to determinate TAC and SSFSC in Chinese vinegar, and NIR spectroscopy has a potential to be used in vinegar industry.     

Changes in aroma quality of ‘Golden Delicious’ apples after storage at different oxygen and carbon dioxide concentrations

‘Golden Delicious’ apples were stored in semicommercial chambers in normal atmosphere and in various controlled atmospheres (CAs) in which oxygen and carbon dioxide contents were held at 10, 20 or 30 l m⁻³ for 3, 5 or 7 months. Following storage, fruits were kept at 20 °C for 1, 5 or 10 days, after which quality parameters were determined and aroma components were obtained and analysed by the dynamic headspace method and quantified by gas chromatography–mass spectrometry. The highest emission of volatile components was obtained after 5 months of storage. Esters were the main compounds released after cold storage in all conditions. Normal cold storage gave the highest amounts of straight‐chain esters, while low‐oxygen atmospheres gave the highest amounts of branched‐chain esters. After 3 and 7 months there were no significant differences in volatiles on comparing fruits from different storage conditions. Low‐oxygen atmospheres had beneficial effects on fruit firmness, titratable acidity and colour. Apples coming from low‐oxygen atmospheres gave the highest sensory score after 5 months of cold storage. © 2000 Society of Chemical Industry     

Estimation of residue depletion of cyadox and its marker residue in edible tissues of pigs using physiologically based pharmacokinetic modelling

Physiologically based pharmacokinetic (PBPK) models are powerful tools to predict tissue distribution and depletion of veterinary drugs in food animals. However, most models only simulate the pharmacokinetics of the parent drug without considering their metabolites. In this study, a PBPK model was developed to simultaneously describe the depletion in pigs of the food animal antimicrobial agent cyadox (CYA), and its marker residue 1,4-bisdesoxycyadox (BDCYA). The CYA and BDCYA sub-models included blood, liver, kidney, gastrointestinal tract, muscle, fat and other organ compartments. Extent of plasma-protein binding, renal clearance and tissue-plasma partition coefficients of BDCYA were measured experimentally. The model was calibrated with the reported pharmacokinetic and residue depletion data from pigs dosed by oral gavage with CYA for five consecutive days, and then extrapolated to exposure in feed for two months. The model was validated with 14 consecutive day feed administration data. This PBPK model accurately simulated CYA and BDCYA in four edible tissues at 24–120 h after both oral exposure and 2-month feed administration. There was only slight overestimation of CYA in muscle and BDCYA in kidney at earlier time points (6–12 h) when dosed in feed. Monte Carlo analysis revealed excellent agreement between the estimated concentration distributions and observed data. The present model could be used for tissue residue monitoring of CYA and BDCYA in food animals, and provides a foundation for developing PBPK models to predict residue depletion of both parent drugs and their metabolites in food animals.     

Analysis of volatile flavour components by dynamic headspace analysis/gas chromatography-mass spectrometry in roasted pistachio extracts using supercritical carbon dioxide extraction and sensory analysis

In this study, optimum process parameters for supercritical carbon dioxide (CO₂) (SC-CO₂) extraction of roasted pistachio (Pistacia vera L.) were investigated by depending on amount of the characteristic flavouring components (α-pinene, limonene-D, α-terpinolene and β-myrcene). The extracts were analysed by DHA/GC-MS for determination of the volatile compounds and the optimum process parameters were decided as 200 g, 350 Bar, 70°C, 75 g _CO2/min and 60 min. In the pistachio extracts obtained having the optimum process parameters, α-pinene, β-myrcene, limonene-D and α-terpinolene were detected as 24.47 g/100 g, 0.52 g/100 g, 2.25 g/100 g and 5.70 g/100 g among 31 volatile compounds in total, respectively. The fatty acid composition of the extract, which had the most desirable taste and flavour, was detected by gas chromatography using fatty acid methyl esters (FAME) preparation. The fatty acid composition analysis showed that the pistachio extract had included mostly oleic acid (67.51%, w/w) and linoleic acid (17.85%, w/w).