乙醇对鲜切西兰花品质及其生理、生化代谢的影响

以西兰花为对象,考察不同浓度乙醇处理的鲜切西兰花在贮藏期内菌落总数、失重率、感官品质、相对电导率、总酚、叶绿素以及多酚氧化酶活性和苯丙氨酸转氨酶活性的变化,探讨不同浓度乙醇溶液对鲜切西兰花生理、生化代谢的影响。研究结果表明,乙醇溶液处理鲜切西兰花,不同程度地保持了鲜切西兰花的质地,延缓了营养物质的损失,抑制了PPO和PAL活性,有效地提高了鲜切西兰花贮藏期间的品质,延长了货架期。     

乙醇熏蒸处理对鲜切西兰花活性成分和抗氧化活性的影响

研究乙醇熏蒸处理对鲜切西兰花总酚、总黄酮、总硫代葡萄糖苷和萝卜硫素等活性成分含量及抗氧化活性的影响。先将花球在20 ℃条件下分别用体积分数为2%、5%、10%、20%乙醇溶液熏蒸处理6 h,再切割成小花并在10 ℃条件下贮藏。结果表明,10%乙醇溶液熏蒸处理可以显著延长鲜切西兰花的货架期、提高总酚和总黄酮含量、延缓总硫代葡萄糖苷和萝卜硫素含量下降,并可有效保持较高的DPPH（1,1-diphenyl-2-picrylhydrazyl）自由基清除能力和还原力,提高其清除超氧阴离子自由基和羟自由基能力,从而延缓西兰花采后衰老、保持较高的抗氧化活性。同时发现,总酚、总黄酮和萝卜硫素含量与DPPH自由基清除能力存在极显著的正相关性。这些结果表明乙醇熏蒸处理在鲜切西兰花保鲜中具有较好的应用前景。     

乙醇熏蒸对番木瓜采后品质和生理指标的影响

为研究乙醇熏蒸对番木瓜采后的保鲜效果,本次实验用不同浓度的乙醇对番木瓜进行熏蒸处理。实验结果表明乙醇熏蒸能够明显减少其可滴定酸、可溶性固形物和VC含量的损失,延缓果实硬度的下降,降低多酚氧化酶活性等生理指标的变化速率。特别是浓度为2.0 m L/kg的乙醇的保鲜效果最佳。这为乙醇熏蒸作为保鲜方法应用于果蔬生产中提供参考依据。      

乙醇熏蒸处理对中华猕猴桃生理代谢及贮藏品质的影响

本研究以中华猕猴桃为实验材料,采用四种浓度0、250、500、1000 μL/L乙醇熏蒸处理,置于0℃贮藏,分别在第0、14、28、42、56、70 d测定其果实硬度、维生素C含量、叶绿素含量、过氧化氢酶(CAT)、多酚氧化酶(PPO)、过氧化物酶(POD)、总酚及类黄酮含量。结果表明:经过乙醇熏蒸处理,呼吸强度明显受到抑制,保持了果实的硬度、减缓了维生素C含量、叶绿素含量的下降速率及褐变发生情况,提高了CAT的活性,保护PPO活性,但对POD影响不显著,同时也提高了总酚、类黄酮等抗氧化物质的含量,达到了保鲜效果,有效延长了中华猕猴桃的货架期。500 μL/L乙醇熏蒸处理能够较好地保护果实的品质,降低酶活性,提高抗氧化物质含量,减缓果实衰老。     

拮抗酵母对西兰花黑斑病及品质的影响

黑斑病是西兰花最常见的采后病害,利用不同浓度拮抗酵母菌悬液可抑制黑斑病,但抑菌效果及对西兰花品质影响尚不清楚。离体试验结果表明,在105~108浓度范围内,随酵母菌悬液浓度增加,黑斑病菌受抑制效果越明显。108 CFU/mL拮抗酵母菌悬液对病原菌菌落生长抑制率最高,为87.9%,对病原菌孢子24 h后的萌发和芽管生长抑制率分别为90.97%,84.05%。活体试验结果表明,西兰花接种105 CFU/mL拮抗酵母菌悬液后,无论是单独存在还是和病原菌同时存在,都能在西兰花伤口处快速繁殖。108CFU/mL拮抗酵母菌悬液处理7 d后西兰花的病斑直径和发病率分别为4.70 mm和21.27%,效果明显好于较低浓度酵母菌处理的西兰花。不同浓度拮抗酵母菌悬液可有效保持西兰花贮藏期间叶绿素、Vc和可溶性糖含量,减缓PPO酶活性升高的趋势,并维持POD酶活性,而108 CFU/mL拮抗酵母菌悬液处理的各项指标优于其他处理组,其保鲜效果最好。因此,拮抗酵母菌可抑制黑斑病菌生长和繁殖,以108 CFU/mL拮抗酵母菌悬液效果为最好,对西兰花PPO酶活性有抑制作用外,对花球其它生理活性无明显影响。     

二氧化氯熏蒸处理对西兰花品质的影响

目的:解决西兰花采后黄化变色和品质保鲜问题。方法:采用不同质量浓度(0,0.2,0.5,1.0,1.5,2.0 mg/L)的二氧化氯(ClO₂)气体于23℃下对西兰花进行熏蒸处理,测定采后西兰花贮藏0,2,4,6,8 d时的感官、颜色、黄化级别以及生理生化指标和相关褐变酶的活性。结果:与对照组相比,不同质量浓度ClO₂均可抑制西兰花的质量损失率、黄化褐变和花蕾的腐败变质;0.5,1.0 mg/L的ClO₂对西兰花的叶绿素含量和色差值a~*、b~*的维持以及PPO、POD酶活性的抑制作用更为显著;其中0.5 mg/L的ClO₂对西兰花花蕾色差值的保持效果最佳,且贮存第8天时黄化级别仍为Ⅱ级,同时有效维持了维生素C含量,延缓了花蕾的黄化褐变。结论:采用ClO₂气体对西兰花进行熏蒸处理需控制其浓度以获得维持采后西兰花花球鲜绿和延长货架寿命的最佳效果。     

臭氧处理对采后西兰花贮藏品质的影响

该文探究在4℃贮藏条件下0、2.14、6.43、10.72 mg/m~3不同浓度的臭氧对采后西兰花贮藏品质的影响。结果表明,与0 mg/m~3相比,臭氧浓度为2.14、6.43、10.72 mg/m~3对采后西兰花多酚氧化酶酶(polyphenol oxidase,PPO)、1-氨基环丙烷-1-羧酸合成酶(1-aminocyclopropane-1-carboxylic acid synthase,ACS)和1-氨基环丙烷-1-羧酸氧化酶(1-aminocyclopropane-1-carboxylate oxidase,ACO)活性均具有抑制效果,同时促进可滴定酸(titratable acid,TA)和维生素C(vitamin C,VC)在贮藏前期的生成,使还原糖、叶绿素含量维持在较高水平,且具有较好的保绿效果。研究表明,不同浓度的臭氧处理对西兰花均具有一定的贮藏保鲜效果,其中,10.72 mg/m~3的臭氧浓度对延缓采后西兰花的衰老和延长贮藏期效果最好。     

UV-C和LED红光复合处理对西兰花贮藏品质的影响

为探究短波紫外线（ultraviolet-C,UV-C）和发光二极管（light emitting diode,LED）红光复合处理对西兰花贮藏品质的影响,本研究采用3 kJ/m2的UV-C辐照和50 μmol/（m2·s）的LED红光辐照单独和复合处理采后西兰花,并将处理后的西兰花贮藏于（20±1）℃条件下,观察其外观品质及生理特性的变化。结果表明：与UV-C、日光（LIGHT）和LED红光分别单独处理西兰花相比,UV-C和LED红光复合处理可有效保持西兰花感官品质,抑制质量损失率和丙二醛含量的增加,延缓叶绿素和VC含量下降,提高过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶活力。综上,UV-C和LED红光复合处理可以有效保持西兰花品质,延长货架期。     

冰温结合1-MCP贮藏对西兰花品质及生理的影响

通过对西兰花在贮藏期间理化指标及营养成分变化规律的分析,探讨冰温结合1-MCP处理对西兰花的保鲜效果。实验结果表明:与直接冰温贮藏相比,冰温结合1-MCP处理对延缓西兰花VC含量和叶绿素含量的下降均有明显效果,可抑制西兰花的呼吸强度和乙烯生成速率,并降低其峰值;且冰温结合1-MCP处理提高了西兰花过氧化物酶（POD）和过氧化氢酶（CAT）的活性,降低了多酚氧化酶（PPO）活性,延缓了相对电导率的升高。这说明西兰花经冰温结合1-MCP处理贮藏的效果优于直接冰温贮藏的效果。      

固载二氧化氯对最小加工竹笋品质和生理的影响

采用固体二氧化氯处理最小加工竹笋,于4 ℃贮藏12 d。以呼吸强度、颜色、硬度、苯丙氨酸解氨酶（PAL）、多酚氧化酶（PPO）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）活性、超氧阴离子自由基生成速率、总抗氧化能力和菌落总数等为指标,研究0.50 mg/L二氧化氯对最小加工竹笋品质和生理的影响。结果表明：用0.50 mg/L的二氧化氯处理,可降低最小加工竹笋呼吸强度,抑制竹笋贮藏期间硬度的上升;延缓PAL、PPO活性的增加;提高CAT、APX和GR的活性,降低超氧阴离子自由基的生成速率,提高总抗氧化能力。     

Modelling the respiration rate of minimally processed broccoli (Brassica rapa var. sylvestris) for modified atmosphere package design

In this work, the effect of temperature, oxygen and carbon dioxide on the respiration rate of minimally processed broccoli was studied to develop suitable modified atmosphere packaging. Respiration rate was measured at 3, 5, 7, 10, 15 and 20 °C under different gas compositions of O₂ and CO₂ (1%, 5%, 10%, 15% and 21% of O₂ with the balance N₂, a mixture of 10% and 20% of carbon dioxide with the balance air and a mixture at 3% of O₂ and 15% of CO₂ with the balance N₂). As expected, temperature was the most influential factor on respiration rate, for all atmospheres tested: increasing the temperature from 3 to 20 °C resulted, for air‐stored samples, in a 84% change in oxygen respiration rate, whereas at constant temperature, the respiration rate decreased by 35% with lowering the O₂ concentration from 21% to 1% and by 44% with increasing the CO₂ concentration from 0% to 20%. The Michaelis and Menten competitive model with maximum respiration rate varying against temperature with an Arrhenius equation accurately described the influence of gas composition and temperature on the respiration rate of minimally processed broccoli, and it was used to design a suitable package.     

臭氧对鲜切青花菜品质的影响

研究了臭氧水浸泡对鲜切青花菜品质的影响。用10mg /L的臭氧水将鲜切青花菜浸泡5 min和15 min后置入0℃冷库贮藏。在贮藏期间发现臭氧抑制了青花菜的黄化,延缓了青花菜中叶绿素的降解,抑制了类胡萝卜素的合成;同时增加了失重率,降低了叶绿素荧光比值Fm/Fv,但对Vc、蛋白质和总酸并没有影响。     

Effect of film and temperature on the sensory, microbiological and nutritional quality of minimally processed cauliflower

The effect of atmosphere modification, generated using three different packaging films, on the quality of cauliflower minimally processed when stored at 4 or 8 °C for up 20 days was evaluated. The colour, texture, weight loss, sensory attributes, as well as microbial counts and sugars and ascorbic acid content were determined. The atmosphere generated with the perforated polyvinylchloride (PVC) film was hardly modified, whereas the other two films (non-perforated PVC and polypropylene films) originated changes in CO₂ and O₂ levels during storage. The different packaging conditions and storage temperature influenced yellowing. An increase in shear force was observed. Weight losses were below 5%. Mesophiles and Pseudomonas counts were below 7 log CFU g⁻¹, the populations being lower with film B and film C than with film A. Cauliflower maintained an acceptable appearance in all the films studied. Total sugars decreased about 27% after 20 days of storage, whereas ascorbic acid did not change.     

Influence of combined hot air and UV-C treatment on the antioxidant system of minimally processed broccoli (Brassica oleracea L. var. Italica)

Broccoli develops a fast senescence that deteriorates the nutritional quality of the product. In this work, a combined treatment with hot air and UV-C were applied to minimally processed broccoli florets to investigate their effects on the antioxidant system during storage at 20 °C. Application of UV-C and heat enhanced by approximately 13% the levels of total antioxidants immediately after treatment. These levels were lower than initials in both control and treated samples. Nevertheless, higher values (ranged from 12 to 50%) were also detected in treated samples during storage. In general, higher values of antioxidants were correlated with elevated levels of phenols (from 10 to 17%) and ascorbic acid (from 11 to 17%) in treated florets. The increment in the content of phenolics in treated broccolis was correlated to an increased phenylalanine ammonia lyase (PAL) activity. The combined treatment also affects the activity of enzymes involved in removal of reactive oxygen species. An increase of about 50% in superoxide dismutase activity was detected after treatment. During the first days of storage this higher activity was about 40%. Enzymes that remove H₂O₂ like catalase and ascorbate peroxidase showed an enhanced activity toward the end of storage. The combined treatment diminished the peroxidase (POX) activity approximately 60% after the treatment and near 50% after two days of storage, suggesting a minor role of this enzyme in detoxification of H₂O₂. In conclusion, combined treatment may contribute to enhance the protection against oxidative molecules not only by increasing levels of phenolics and ascorbic acid but also by enhancing the activity of enzymes involved in removing reactive oxygen species.     

柠檬酸和异抗坏血酸钠处理对冷藏鲜切菠萝质量的影响

采用响应面方法,研究柠檬酸、异抗坏血酸钠处理和冷藏时间对鲜切菠萝颜色、硬度、失重和包装内气体组成的影响。新鲜菠萝片分别用0%～1.0%的柠檬酸和异抗坏血酸钠处理3min,然后装在塑料泡沫碟中,用PVC薄膜密封,在5℃冷库中贮藏0～14d。结果表明,异抗坏血酸钠显著地减缓L、a、b、失重(p≤0.001)和硬度(p≤0.1)的变化,但对包装内O2和CO2含量没有影响。柠檬酸对L、硬度和失重有影响(p≤0.1)。所有考察的指标在贮藏过程中均显著变化(p≤0.01)。建立的回归模型可充分预测柠檬酸、异抗坏血酸钠处理和冷藏时间对鲜切菠萝质量的影响。     

Effect of plastic permeability and exposure to light during storage on the quality of minimally processed broccoli and cauliflower

The impact of lighting on minimally processed broccoli and cauliflower packaged in four different film types (PVC and three P-Plus) has been measured and compared. The effect on the sensory quality of storage at 4 °C in darkness and under lighting was evaluated. The gas concentration in the packages, pH, mesophilic counts and weight loss was also determined.Neither the type of film used for packaging nor the storage conditions led to changes in the evolution of pH or the microorganism count in broccoli and cauliflower. However, exposure to light stimulated stomatic opening facilitate the exchange of gases between the plant tissue and the atmosphere within the packaging. Thus, a considerable loss of water vapor was observed in the packages of both vegetables stored in the presence of illumination. Moreover, exposure to light stimulated respiratory activity so that for the cauliflower, the composition of the atmosphere within the packages varied depending on the permeability of the packaging film used and the storage conditions. However, in the case of the broccoli, the increase in respiratory activity due to the lighting was compensated by the photosynthetic activity which took place in these conditions, in such a way that the composition of the atmosphere inside the packs solely depended on the permeability of the film.This difference in the physiological response conditioned the most suitable kind of packaging film in each case. For cauliflower, in conditions of darkness, P-Plus 120 film proved the most suitable for preserving its sensory qualities, while under conditions of lighting, this film did not prove suitable due to its low permeability. However, in broccoli the different packaging films tested behaved in a very similar way whether stored under lighting or in the dark.     

Ultrasound decontamination of minimally processed fruits and vegetables

The effectiveness of power ultrasound for the microbial decontamination of minimally processed fruits and vegetables was studied. Reductions in Salmonella typhimurium attached to iceberg lettuce obtained by cleaning with water, chlorinated water, ultrasound with water and ultrasound with chlorinated water were 0.7, 1.7, 1.5 and 2.7 logs, respectively, for small-scale (2 L) trials. The cleaning action of cavitation appears to remove cells attached to the surface of fresh produce, rendering the pathogens more susceptible to the sanitizer. For large-scale (40 L) trials, the addition of chlorine to water in the tank gave a systematic difference in Escherichia coli decontamination efficiency. However, the frequency of ultrasound treatment (25, 32–40, 62–70 kHz) had no significant effect on decontamination efficiency ( P  > 0.69). With the potentially high capital expenditure together with the expensive process of optimization and water treatment, it is unlikely that the fresh produce industry would be willing to take up this technology. Furthermore, the additional one log reduction achieved by applying ultrasound to a chlorinated water wash does not completely eliminate the risk of pathogens on fresh produce.     

Semi-industrial production of a minimally processed infant formula powder using membrane filtration

Infant formula (IF) is submitted to several heat treatments during production, which can lead to denaturation or aggregation of proteins and promote Maillard reaction. The objective of this study was to investigate innovative minimal processing routes for the production of first-age IF powder, thus ensuring microbial safety with minimal level of protein denaturation. Three nutritionally complete IF powders were produced at a semi-industrial scale based on ingredients obtained by fresh bovine milk microfiltration (0.8 and 0.1-µm pore size membranes). Low-temperature vacuum evaporation (50°C) and spray-drying (inlet and outlet temperatures of 160 and 70°C, respectively) were conducted to produce the T? formula with no additional heat treatment. The T+ formula was produced with a moderate heat treatment (75°C for 2 min) applied before spray-drying, whereas the T+++ formula received successive heat treatments (72°C for 30 s on the milk; 90°C for 2–3 s before evaporation; 85°C for 2 min before spray-drying), thus mimicking commercial powdered IF. Protein denaturation and Maillard reaction products were followed throughout the production steps and the physicochemical properties of the powders were characterized. The 3 IF powders presented satisfactory physical properties in terms of a_w, free fat content, glass transition temperature, and solubility index, as well as satisfactory bacteriological quality with a total flora <10³ cfu/g and an absence of pathogens when a high level of bacteriological quality of the ingredients was ensured. Protein denaturation occurred mostly during the heat treatments of T+ and T+++ and was limited during the spray-drying process. The IF powder produced without heat treatment (T-) presented a protein denaturation extent (6 ± 4%) significantly lower than that in T+++ (58 ± 0%), but not significantly different from that in T+ (10 ± 4%). Although T? tended to contain less Maillard reaction products than T+ and T+++, the Maillard reaction products did not significantly discriminate the infant formulas in the frame of this work. The present study demonstrated the feasibility of producing at a semi-industrial scale an infant formula being bacteriologically safe and containing a high content of native proteins. Application of a moderate heat treatment before spray-drying could further guarantee the microbiological quality of the IF powders while maintaining a low protein denaturation extent. This study opens up new avenues for the production of minimally processed IF powders.     

天然物质对切割蔬菜中常见微生物的抑制作用研究

研究了正离子水和姜黄、虎杖、艾叶、丁香提取物对切割蔬菜中常见微生物(大肠杆菌、荧光假单胞菌、啤酒酵母)的抑制作用,结果表明:正离子水对大肠杆菌、荧光假单胞菌、啤酒酵母无抑制作用,抑制率均为0;姜黄、虎杖、艾叶、丁香提取物对3种微生物均有一定的抑制作用。适宜温度培养7d后,姜黄、虎杖、艾叶、丁香提取物对大肠杆菌的抑制率从大到小依次为:姜黄(51.7%),艾叶(37.2%),虎杖(36.5%),丁香(30.4%);对荧光假单胞菌的抑制率从大到小依次为:丁香(100%),姜黄(55.8%),艾叶(55.8%),虎杖(46.7%);对啤酒酵母的抑制率从大到小依次为:丁香(100%),姜黄(35.3%),艾叶(35.3%),虎杖(33%)。