外源抗坏血酸和谷胱甘肽对荔枝保鲜效果的影响

为了探讨外源抗坏血酸（AsA）和谷胱甘肽（GSH）对荔枝保鲜效果的影响。分别在多菌灵500 mg/L+施保克 3 mL/L+ 柠檬酸15.0 mmol/L溶液中分别加入抗坏血酸50.0 mmol/L（AsA处理）和谷胱甘肽50.0 mmol/L（GSH处理）浸果5 min,以多菌灵500 mg/L+施保克3 mL/L+柠檬酸15.0 mmol/L浸果5 min为对照处理,分别置于常温和6℃低温贮藏、相对湿度为80%。结果表明：AsA和GSH处理均能降低荔枝果皮多酚氧化酶（PPO）活性和相对电导率;提高果肉的超氧化物岐化酶（SOD）和过氧化氢酶（CAT）活性;降低果肉过氧化氢（H2O2）和丙二醛（MDA）的含量,维持果肉中较高的维生素C和GSH含量。低温下,AsA和GSH处理均能提高荔枝保鲜效果,降低果实的腐烂率,但AsA处理的保鲜效果要优于GSH处理的效果,而常温下GSH处理并不能提高荔枝的保鲜效果。     

不同气调包装对冷藏鱼糜制品品质的影响

为分析不同气调包装对鱼糜制品冷藏过程中品质的影响,研究以鱼糜制品中的鱼丸为对象,通过测定其在 （0±0.5）℃冷藏过程中的菌落总数、理化和感官等指标的变化,评价气调包装的保鲜效果。气调包装条件分别为空气包装（对照）、低氧气调包装（60%CO2+10%O2+30%N2,均为体积分数,下同）、无氧气调包装（60%CO2+40%N2）、含保鲜剂的无氧气调包装（60%CO2+40%N2+保鲜剂）。结果表明,0℃下鱼丸在空气包装下贮藏32 d和低氧气调包装下贮藏42 d后菌落总数分达到8.7×104 cfu/g和8.5×104 cfu/g,超过规定的卫生标准;而无氧气调包装可使鱼丸的货架期达到47 d（菌落总数4.3×104 cfu/g）以上,含保鲜剂的无氧气调包装可使鱼丸货架期延长至52 d（菌落总数0.98×104 cfu/g）以上,并且能降低脂肪氧化程度;两组无氧气调包装样品在冷藏期间其pH值、TBA（硫代巴比妥酸）值和感官等指标都优于低氧气调包装和空气包装。无氧气调包装或结合生物保鲜剂包装能更好地延长冷藏鱼丸的货架期。     

Effect of different treatments on the evolution of polyamines during refrigerated storage of eggplants

The applicability of a thermal treatment was compared with modified-atmosphere (MA) storage in relation to chilling injury (CI) and polyamines evolution in eggplants. Fruits underwent physiological disorders at 3 degrees C, evidenced by the appearance of surface injuries at the third day of storage, and, after moving the fruits to 20 degrees C, by increased respiratory activity and more intense ethylene production. Storage of fruits in sealed low-density polyethylene bags and a previous treatment with heated air (1 h at 35 degrees C) were both effective in retarding chilling injury, though the former was better. Two free polyamines were found in cv. Black Nite: putrescine, in greater proportion, and spermidine. Putrescine increased in control (untreated) fruits stored at 3 degrees C in parallel with the external appearance of chilling injury, whereas this increase was either not exhibited or retarded in treated or MA stored fruits. Spermidine did not change in control fruits at 3 degrees C, remaining almost constant over the whole storage period, whereas in heat- and MAP-treated fruits spermidine levels exhibited a decrease.     

Effects of ultra-high-pressure homogenization treatment on the lipolysis and lipid oxidation of milk during refrigerated storage

Free fatty acid (FFA) release and quantification and lipid oxidation extent of ultra-high-pressure homogenized (UHPH) milk samples were evaluated to assess the effect of UHPH on the susceptibility of milk lipids to lipolysis and oxidation. Milk was UHPH-treated at 200 and 300 MPa with inlet temperatures of 30 and 40 degrees C. UHPH-treated samples were compared to high-pasteurized milk (PA; 90 degrees C, 15 s). Results showed that all FFA increased significantly during storage only in 200 MPa samples. Lipid oxidation was measured as an accumulation of lipid hydroperoxides as the primary oxidation product and malondialdehyde and hexanal as the secondary oxidation products. Samples treated at 300 MPa presented higher malondialdehyde and hexanal content compared to 200 MPa treated-samples and to PA milk.     

Degradation kinetics of the antioxidant additive ascorbic acid in packed table olives during storage at different temperatures

The kinetics of ascorbic acid (AA) loss during storage of packed table olives with two different levels of added AA was investigated. Three selected storage temperatures were assayed: 10 degrees C, ambient (20-24 degrees C), and 40 degrees C. The study was carried out in both pasteurized and unpasteurized product. The effect of pasteurization treatment alone on added AA was not significant. In the pasteurized product, in general AA degraded following a first-order kinetics. The activation energy calculated by using the Arrhenius model averaged 9 kcal/mol. For each storage temperature, the increase in initial AA concentration significantly decreased the AA degradation rate. In the unpasteurized product, AA was not detected after 20 days in samples stored at room temperature and AA degradation followed zero-order kinetics at 10 degrees C, whereas at 40 degrees C a second-order reaction showed the best fit. In both pasteurized and unpasteurized product, the low level of initial dehydroascorbic acid disappeared during storage. Furfural appeared to be formed during storage, mainly at 40 degrees C, following zero-order kinetics.     

Consequences of microwave heating and frying on the lipid fraction of chicken and beef patties

Two types of commercial meat patties were analyzed to evaluate the effect of two applied cooking methods on the lipid fraction and the cholesterol oxidation process during heating. Microwave heating hardly modified the fatty acid profiles of both chicken and beef patties, whereas frying in olive oil increased oleic and eicosapentaenoic acids and decreased linoleic and docosahexaenoic acids in both types of products. Frying improved the omega6/omega3 fatty acids ratio in beef patties from 10.67 (raw) to 5.37 (fried). Total cholesterol oxidation product (COP) increments were 5.3-6.1-fold with microwave heating and 1.5-2.6-fold with frying. Chicken patties, raw and cooked, had a COP content twice as high as the corresponding beef ones.     

柑橘幼果提取物对猪肉冷藏过程中抗脂质氧化影响

为了研究不同浓度的柑橘幼果乙醇提取物（CE）在新鲜猪肉中的抗脂质氧化和抑菌作用。在冷藏（4℃）条件下对鲜猪肉进行以下5种处理：对照组（不添加保鲜剂）;AC-0.02（添加0.02%抗坏血酸）;CE-0.05（添加0.05%柑橘幼果醇提物,下同）,CE-0.1和CE-0.2。在12 d的冷藏（4℃）过程中,各样品的pH值均显著降低（p＜0.05）,而硫代巴比妥酸值（TBARS）和游离脂肪酸的含量显著增加（p＜0.05）。CE-0.1和CE-0.2处理组的菌落总数在贮藏过程中均低于对照组。CE的加入使猪肉样品的L*值和a*值都显著下降,在贮藏过程中,CE处理组样品的b*值均高于对照组,且随着CE浓度的增加,b*值增大。5组试验样品中,经CE-0.2处理的样品TBARS值和游离脂肪酸含量最低;对照组的过氧化值在第6天达到最大值,随后逐渐减小,而其它处理组的过氧化值在储藏期间均呈上升趋势。在贮藏1 d后,各处理组中的共轭二烯值均小于对照组。结果表明,柑橘幼果醇提物可作为肉制品的保鲜剂,能有效抑制新鲜猪肉贮藏过程中的脂质氧化和腐败微生物的生长。为开发柑橘幼果天然提取物保鲜剂提供理论参考。     

Quality indicators of cultured Newfoundland blue mussels (Mytilus edulis) during storage on ice: microbial growth, pH, lipid oxidation, chemical composition characteristics, and microbial fatty acid contents

To devise proper strategies to evaluate and maintain the quality of cultured blue mussels (Mytilus edulis) during storage on ice, this study examined the potential use of microbial growth, pH, lipid oxidation, and composition characteristics as quality indicators. It also evaluated the use of individual (i15:0, ai15:0, i16:0, ai16:0, i17:0, ai17:0, 17:0) and total bacterial fatty acid contents as a rapid method to examine the microbial quality of stored mussels. Linear regression analyses of the storage period of mussels vs various quality indicators indicated that the strongest correlation was between the storage period and microbial growth (r = 0.973, p < 0.0001) followed by the microbial fatty acid ai15:0 content (r = 0.903, p < 0.0001) and ash content (r = 0.819, p = 0.0002). All other correlations between the storage period and quality indicators were moderate (r = 0.500-0.700 and p < 0.05), poor (r < 0.500 and p > 0.05), or negative (r = -0.657 and p = 0.027).     

The effect of tillage systems on some microbial characteristics

Soils were sampled from plots with four variants of tillage methods: (1) conventional tillage (CT); (2) no tillage (NT); (3) minimum tillage (MTS); and (4) no tillage + mulch (NTM). Our aim was to study the influence of tillage on selected soil microbial properties. Determination of urease, dehydrogenase, invertase, arylsulphatase, potential nitrogenase activity, CFU of Azotobacter spp., and carbon microbial biomass has been conducted for time period 2002–2007. Soil samples from 0–0.1 m, 0.1–0.3 m, and 0.3–0.5 m were collected in the spring and autumn. Enzymatic activities (dehydrogenase, urease, arylsulphatase, and invertase) were significantly affected by soil depth and the tillage system employed. The statistically significant higher activity of urease was measured using the minimum tillage system (MTS), compared to the conventional tillage (CT) at soil depths of 0–0.1 m. The highest dehydrogenase activity was measured during the protective tillage treatment (NTM – no tillage with mulch). As far as other enzymatic activities (invertase and arylsulphatase) are concerned, the highest values were recorded in the protective tillage treatments. The highest counts of Azotobacter spp., as well as the highest nitrogenase activity (both statistically significant) were found in the no tillage + mulch (NTM) variant, at depths of 0.1–0.3 m. Microbial biomass (C-biomass) was the highest with the minimum tillage (MTS). The results show a positive influence of protection soil tillage on the reviving of upper layer of topsoil, especially in the variants where soil was supplied with organic matter.     

包装方式对牛肉贮藏过程中蛋白质氧化及降解的影响

为探明托盘透氧包装(air packaging,AP)和高氧气调包装(modified atmosphere packaging,MAP,80%O2+20%CO2)对宰后牛肉贮藏过程中对牛肉嫩度影响的潜在机制,以真空包装(vacuum packaging,VP)为对照,选取6头西门塔尔纯种母黄牛背最长肌,分别进行托盘透氧包装、真空包装和高氧气调包装,4℃冷库分别贮藏0、4、7、10 d,分别测定蛋白羰基含量及分布、蛋白表面疏水性值、蛋白质溶解度值以及肌间线蛋白和肌联蛋白的降解变化。结果表明:相对于真空包装组,托盘包装组和高氧气调包装组在宰后贮藏过程中肌细胞外围出现羰基氧化荧光信号显著增加,且不断向细胞内部扩散,说明其蛋白质氧化程度不断增加;宰后贮藏10 d后,托盘透氧包装组和高氧气调包装组的蛋白质表面疏水性显著高于真空包装组(P0.05),而托盘透氧包装组和高氧气调包装组的蛋白溶解性显著低于真空包装组(P0.05);宰后贮藏7和10 d,托盘透氧包装组和高氧气调包装组的肌间线蛋白和肌联蛋白的降解显著低于真空包装组(P0.05),说明托盘透氧包装组和高氧气调包装组抑制了肌间线蛋白和肌联蛋白的降解(P0.05)。托盘透氧包装组和高氧气调包装组能够提高宰后贮藏过程中蛋白质氧化程度,从而抑制其对牛肉骨骼关键蛋白的降解,该研究可为牛肉贮藏提供理论支撑。     

Changes in volatile compounds of carrots (Daucus carota L.) during refrigerated and frozen storage

Carrots (Daucus carota L.) of cv. Bolero and cv. Carlo were processed into shreds and stored for up to 4 months at -24 degrees C (frozen storage), or the roots were stored for up to 4 months at 1 degrees C (refrigerated storage) followed by processing into shreds. Volatiles from the carrot shreds were collected by dynamic headspace technique and analyzed by GC-FID, GC-MS, GC-MS/MS, and GC-O to determine the volatile composition and aroma active components of carrots stored under different temperature conditions. A total of 52 compounds were quantified, of which mono- and sesquiterpenes accounted for approximately 99% of the total volatile mass. Major volatile compounds were (-)-alpha-pinene, beta-myrcene, (-)-limonene, (+)-limonene, (+)-sabinene, gamma-terpinene, p-cymene, terpinolene, beta-caryophyllene, alpha-humulene, and (E)- and (Z)-gamma-bisabolene. A considerable increase in the concentration of mono- and sesquiterpenes was observed during refrigerated storage, whereas the concentration of terpenoids was around the same level during frozen storage. GC-O revealed that the major volatiles together with (+)-alpha-pinene, (-)-beta-pinene, (+)-beta-pinene, 6-methyl-5-hepten-2-one, (-)-beta-bisabolene, beta-ionone, and myristicin had an odor sensation, which included notes of "carrot top", "terpene-like", "green", "earthy", "fruity", "citrus-like", "spicy", "woody", and "sweet".     

Biochemical and microbial changes during the storage of minimally processed cantaloupe

The effect of storage time on pH, titratable acidity, degrees Brix, organic acids, sugars, amino acids, and color of minimally processed cantaloupe melon (Cucumis melo L. var. reticulatus Naud. cv. Mission) was determined at 4 degrees C and 20 degrees C. Changes in most of the biochemical parameters with storage time were relatively slow at the lower temperature. At 20 degrees C, a 17% loss in soluble solids and a 2-fold increase in acidity occurred after 2 days. Organic acid content also increased considerably with time at this temperature as a result of the production of lactic acid. Oxalic, citric, malic, and succinic acids were the organic acids, and glucose, fructose, and sucrose were the sugars present in the freshly cut cantaloupe. Malic acid concentration decreased concurrently with lactic acid production indicating the possible involvement of anaerobic malo-lactic fermentation along with sugar utilization by lactic acid bacteria. The effect of storage on microbial growth was determined at 4, 10, and 20 degrees C. Gram-negative stained rods grew at a slower rate at 4 degrees C and 10 degrees C than the Gram-positive mesophilic bacteria that dominated microorganism growth at 20 degrees C. Eighteen amino acids were identified in fresh cantaloupe: aspartic acid, glutamic acid, asparagine, serine, glutamine, glycine, histidine, arginine, threonine, alanine, proline, tyrosine, valine, methionine, isoleucine, leucine, phenyl alanine, and lysine. The dominant amino acids were aspartic acid, glutamic acid, arginine, and alanine. Total amino acid content decreased rapidly at 20 degrees C, but only a slight decrease occurred at 4 degrees C after prolonged storage. Changes in lightness (L), chroma, and hue at both temperatures indicate the absence of browning reactions. The results indicate the potential use of lactic acid and lactic acid bacteria as quality control markers in minimally processed fruits.     

不同组分气调包装牛肉冷藏保鲜效果的研究

为延长生鲜牛肉的货架期,保持良好色泽,该文研究了以不同比例组合的CO₂、O₂、N₂作为气调包装对低温保藏的新鲜牛臀肉品质的影响。以真空包装为对照,对保藏期间牛肉色泽、菌相变化、失重率、pH值、挥发性盐基氮等参数跟踪分析,确定最佳的气调包装组分为45% O₂、45% CO₂和10% N₂ ,温度0～4℃,在此条件下牛臀肉可以保藏20 d,并保持色泽稳定。     

不同冰温条件对长期贮藏牛肉品质和货架期的影响研究

该研究旨在探究标准冰温（实验室恒温条件,-2～0 ℃）和商业冰温（工厂冰温库（-4～4 ℃））对长期贮藏牛肉品质的影响,以此明确当前商业冰温条件对牛肉的保鲜效果。试验测定了贮藏期间（20周）两种冰温条件下真空包装牛肉的pH值、肉色、微生物菌落数、挥发性盐基氮（total volatile base-nitrogen,TVB-N）、脂肪氧化和感官品质等指标。结果表明：2种冰温条件下,牛肉在20周的贮藏期内均可以维持良好的肉色及感官品质。贮藏第9周时,商业冰温条件下牛肉样品的菌落总数和TVB-N值就已分别达到7.09 lg CFU/cm2和15.59 mg/100g。而标准冰温条件下的牛肉样品在贮藏期间其菌落总数始终低于7.00 lg CFU/cm2,TVB-N值在贮藏第12周时才超出限量阈值（≤15 mg/100 g）,达到16.66 mg/100 g。总体来看,标准冰温条件对真空包装牛肉的保鲜效果更佳,依据TVB-N值的限量标准,建议标准冰温和商业冰温条件下牛肉的货架期分别不超过9周和12周。     

Stabilizing effect of ascorbic acid on flavan-3-ols and dimeric procyanidins from cocoa

Cocoa flavanols and procyanidins have numerous biological activities. It is known that (-)-epicatechin, (+)-catechin, epicatechin-(4beta-8)-epicatechin (dimer B2), and epicatechin-(4beta-6)-epicatechin (dimer B5) are unstable at physiologic pH, degrading almost completely within several hours, whereas they are relatively stable at pH 5.0. The present study investigated the effects of ascorbic and citric acid on the stability of monomers and dimers in simulated intestinal juice (pH 8.5) and in sodium phosphate buffer (pH 7.4). The addition of ascorbic acid to the incubation mixture significantly increased the stability of the monomers and dimers, whereas the addition of citric acid provided no protective effects. LC-MS showed that with the degradation of dimer B2 and dimer B5, doubly linked A-type dimers were formed. The present results, although not directly transferable to in vivo conditions, suggest that ascorbic acid may stabilize cocoa flavanols and procyanidins in the intestine where the pH is neutral, or alkaline, before absorption.     

嫩茎花椰菜在不同气调贮藏下叶绿素和维生素C的降解及活化能研究

通过检测叶绿素和维生素C的变化，试验确定了花椰菜气调贮藏中主要成份的降解为一级动力学反应；根据Arrhenius方程，确定了不同气调贮藏条件下花椰菜主要成份的表观活化能。在两种温度2℃和8℃，两种气体组分3% O₂，2% CO₂，95% N₂和6% O₂，6% CO₂，88% N₂组合条件下贮藏试验，结果表明在2℃，3% O₂，2% CO_{2相似文献}   

Effect of drying conditions and storage period on polyphenolic content, antioxidant capacity, and ascorbic acid of prunes

In this study the main chemical parameters, ascorbic acid and polyphenol content, and antioxidant activity of two varieties of prunes, dried by high-temperature (85 + 70 degrees C) and low-temperature (60 degrees C) procedures, were monitored during storage. Ascorbic acid content was higher in the prunes dried at 60 degrees C but significantly decreased in both varieties during storage. The different classes of polyphenols analyzed (cinnamates, anthocyanins, flavonols) showed different stabilities during storage. Neochlorogenic acid decreased only in the President variety, whereas chlorogenic acid increased in both varieties; anthocyanins, present only in the President prunes, disappeared in the first months of storage, and the flavonol content fell significantly in both cultivars during the year of the study. Drying temperature significantly affected the polyphenol content, with different effects according to the class of polyphenols. Antioxidant activity showed a significant increase at the end of the storage period and in the President variety was higher in the sample dried at the higher temperature.     

Selective sterilisation of undisturbed soil cores by gamma irradiation: Effects on free-living nematodes,microbial community and nitrogen dynamics

The techniques available for sterilisation or defaunation of soil in ecological experiments mostly have strongly unwanted effects on soil structure and the dynamics of major nutrients such as nitrogen. The potential for using gamma irradiation to prepare defaunated soil microcosms was investigated by subjecting undisturbed soil cores to a range of irradiation doses (0, 5, 10, 20 and 40 kGy). The absence of living nematodes at the lowest irradiation dose was confirmed by microscopic observation. The effects of irradiation dose on mineral nitrogen (as NO₃⁻ and NH₄⁺), microbial biomass C (C_mic), and phospholipid fatty acid (PLFA) concentration and composition were determined over a 4 week incubation period. An increase in the concentration of NO₃⁻ occurred during the incubation period after exposure to 0, 5 and 10 kGy but was barely detectable at 20 and 40 kGy. The effect of irradiation dose on NH₄⁺ release was complex and highly variable within treatments, with the 10 kGy dose resulting in the highest concentrations. Microbial biomass carbon was significantly reduced following a 20 kGy irradiation dose and below detection at 40 kGy. Most remarkably, the sum of all measured PLFAs did not differ significantly between most treatments and was not correlated with microbial biomass. In most cases the concentration of signature fatty acids only differed significantly between the control and the highest irradiation dose treatments. To ascertain the sensitivity of microbial taxa to acute gamma irradiation with accuracy, measures of microbial community structure other than PLFA analysis are needed.     

塑料薄膜覆盖对牛粪便温室气体排放的影响

为控制短期贮存畜禽粪便的温室气体排放,该文研究了塑料薄膜覆盖对肉牛粪便短期贮存过程中温室气体排放量的影响。试验采用静态箱-气相色谱法观测了秋季(日均22.87℃)肉牛粪便自然露天堆放(对照组)和塑料薄膜覆盖堆放(覆盖组)时温室气体的排放通量。结果表明:秋季覆盖塑料薄膜贮存粪便可使N2O和CO2的日均排放通量分别降低94.85%(P0.01)和88.85%(P0.01),并在试验前期(0~9 d)使CH4的日均排放通量降低了43.37%(P0.05),但随后的10~30 d,覆盖组粪便CH4的日均排放通量极显著高于对照组(P0.01)。结论:当环境温度在17.23~30.35℃时,覆盖塑料薄膜可以降低堆放贮存(0~30 d)粪便N2O和CO2的排放通量以及堆放初期(0~9 d)CH4的排放通量。因此,塑料薄膜覆盖贮存法可显著降低粪便堆放初期的温室气体排放。