Cultivar variation in response of strawberry fruit to high carbon dioxide treatments

The influence of cultivar on responses of strawberry fruit to 20 kPa CO₂ or air storage at 2 °C was measured for 7 days. CO₂ storage increased firmness of all cultivars over air storage, but the degree of increase was affected by cultivar and days in storage. CO₂‐treated fruit were lighter colored and less intensely red than air‐treated fruit. Accumulations of acetaldehyde, ethanol and ethyl acetate in CO₂‐treated fruit were strongly affected by cultivar, with those in ‘Annapolis’ having the lowest and those in ‘Governor Simcoe’ having the highest concentrations. Genetic variation in this response provides useful material for investigating the metabolic basis of CO₂ effects in strawberry fruit. © 1999 Society of Chemical Industry     

Antioxidant enzyme activities and antioxidant capacity in longissimus muscle from bulls fed diets rich in polyunsaturated fatty acids

The effect of a treatment diet composed of grass silage and concentrate including rapeseed (with/without feeding restriction) was compared with a control diet of maize silage/grass silage (70:30) and concentrate including soybean, on the antioxidant enzyme activities of fresh longissimus muscle from German Simmental bulls. Additionally, the effect of diet on antioxidant capacity (AOC) of hydrophilic and lipophilic antioxidants was evaluated in fresh and stored beef muscle using the FRAP-ferric reducing ability and TEAC – Trolox-equivalent antioxidant capacity assays at different reaction times. Catalase and superoxide dismutase activities were significantly higher in the treatment diet groups, and glutathione peroxidase activity was not different. AOC was not affected by the diet. However, storage affected the values of FRAP and TEAC assays, and the results were time-depending. 30 min were found like a minimum reaction time for both assays. Generally, AOC values of the hydrophilic antioxidants were significantly higher than lipophilic values.     

Effects of selected plant extracts on anti-oxidative enzyme activities in rats

The effects of plant extracts on the activity of anti-oxidative enzymes in rats were investigated. Sprague-Dawley rats were fed with the extracts and fractions from Rhus javanica, Malus sieboldii, and Ostrya japonica, and the activities of anti-oxidative enzymes, such as superoxide dismutase (SOD) and catalase (CAT) were investigated. SOD activities in blood serum and liver increased following an injection of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH), and these increases were not cancelled out by feeding plant extracts. CAT activities in blood serum and liver increased following the AAPH injection, but these increases were reversed by feeding the extracts of R. javanica and O. japonica. This finding was similar to the result that the CAT activity increase induced by feeding alcohol was cancelled out by feeding ascorbic acid. These results suggest that anti-oxidative polyphenolics from these plants may act through the same mechanism as that of the well-known antioxidant ascorbic acid towards hydrogen peroxide.     

Diffusion of carbon dioxide in tomato fruits during cold storage in modified atmosphere

Treatments with 20% CO₂ of tomato fruit produced a beneficial extension of storage life. The diffusion of CO₂ in tomato (Lycopersicon esculentum Mill) cv. Platense was measured chromatographically and the concentration profiles in the internal gaseous atmosphere of the fruit were determined for non-steady state conditions to establish minimum treatment times that can ensure adequate penetration of the gas.
The effective diffusivity of CO₂ in the tissue was determined by fitting concentration data, obtained from experiments with whole fruit without skin, to the non-steady state solution of the diffusion equation, assuming negligible external mass transfer resistance. The diffusivity was modelled using Maxwell-Eucken expressions, taking account of the heterogeneous structure of the tissue.
The resistance of the fruit skin was evaluated using whole fruits with the stem scar covered with paraffin and fitting experimental data to the solution in terms of mass Biot number; the specific resistance of the peel was some 200 times greater than that of the stem scar.     

Resistance and some enzyme activities in Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) in relation to carbon dioxide enriched atmospheres

Two populations (S-1 and S-2) of the psocid, Liposcelis bostrychophila Badonnel were exposed to carbon dioxide enriched atmospheres. Carbon dioxide resistance developed at steady rates in these two populations during this study period. Selection with 35 and 55% CO(2) resulted in resistance development as expressed by LT(50). Resistance increased steadily under continuous selection to 4.6- and 5.3-fold by generation F(30) for S-1 and S-2, respectively. Throughout the selection process, the slopes of regression lines were always lower than that of the control. The results of biochemical assays showed that the activities of carboxyl esterase (CarE) and superoxide dismutase (SOD) in vitro increased in the selection process. Exposure to higher CO(2) content (HCC) resulted in a gradual decrease in CarE activity in both selected and control populations. Although the induction effect of CO(2) on SOD was brief, the induction times for the S-1 and S-2 were greater than those of the control. The elevated catalase (CAT) activity in association with resistance development was also evident, but no statistical correlation was found between CAT activity and HCC resistance. No significant differences were found in acid phosphatase and alkaline phosphatase activities in both selected and control populations during this study. This study demonstrated that high CarE and SOD activities were positively correlated to CO(2) resistance.     

Effect of muscle and post-mortem rate of pH and temperature fall on antioxidant enzyme activities in beef

The aim of this study was to investigate the effect of muscle, inner and outer Musculus biceps femoris (IBF and OBF respectively) and Musculus longissimus dorsi (LD), on the post-mortem rate of pH and temperature fall, and the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) during simulated retail display. At day 0 of display (2 days post-mortem), the CAT and GSH-Px activities were lower in IBF than in OBF and LD (P < 0.001), and the SOD activity was lower in OBF compared to IBF and LD (P < 0.001). At day 10 of display, SOD and CAT activities had decreased in all three muscles compared to day 0 (P < 0.001), whereas the GSH-Px activity did increase with time of display. Across muscles, there were significant relationships between temperature fall, colour, lipid and colour stability and antioxidant enzyme activities.     

冷藏期间苹果果实能量和NADP-苹果酸酶及基因表达的变化

为研究冷藏期间苹果果实能量水平和NADP-苹果酸酶（NADP-ME）及基因表达的变化情况,本研究以‘长富2’苹果果实为实验材料,定期测定果实硬度、可溶性固形物等品质指标和能量相关物质三磷酸腺苷（ATP）、二磷酸腺苷（ADP）、磷酸腺苷（AMP）含量和能荷变化及NADP-ME、琥珀酸脱氢酶（SDH）活性。结果显示,冷藏期间,‘长富2’果实ATP含量贮藏前60 d下降,而后恢复到贮藏初期水平,ADP和AMP贮藏前60 d稍有降低后,随时间延长显著增加;NADP-ME和琥珀酸脱氢酶（SDH）活性均随贮藏时间延长逐渐降低;辅酶Ⅱ（NADP+）和还原型辅酶Ⅱ（NADPH）含量在贮藏前120 d先增加后下降,与能荷变化相似;Mdcy ME1-Mdcy ME3基因表达虽在时间上有一定差异,但表现出相似的先增加后下降的趋势。冷藏期间苹果果实能量水平和利用效率发生了改变,且能量水平与NADP-ME活性及其基因表达在统计学上存在相关性。      

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。