鲜切西兰花在贮藏过程中自身抗氧化活性的变化

目的研究鲜切西兰花在4℃条件下贮藏14 d内自身抗氧化活性的变化。方法采用DPPH体系、Fenton体系和还原体系研究鲜切西兰花在贮藏期间抗氧化能力的变化。同时还测定了与西兰花抗氧化能力有关的营养成分与酶活性的变化,包括总酚和VC、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和超氧化物歧化酶(SOD)。结果鲜切西兰花在贮藏期间总抗氧化能力在贮藏前12 d呈逐渐上升状态,之后缓慢降低;清除羟自由基的能力很高,但在贮藏期内呈先缓慢降低后回升的趋势;还原能力在贮藏前10 d呈上升趋势,之后大幅度降低。总酚和APX活性均呈先上升后下降的趋势;VC含量从80 mg/100 g降低到60 mg/100 g,之后变化不大;CAT活性和SOD活性在贮藏前期呈现降低趋势,中期回升,后期又逐渐降低。结论鲜切西兰花的抗氧化能力在8~12 d期间较高。     

电生功能水用于提高鲜切马铃薯产品品质的试验研究

对电生功能水杀灭鲜切马铃薯表面微生物以及抑制马铃薯切片氧化褐变的效果进行了研究。用电生功能水及自来水分别处理经过大肠杆菌O78，金黄色葡萄球菌26003，枯草芽胞杆菌1．1849三种微生物接种的马铃薯切片，对处理后其微生物指标进行了观察。试验发现采用普通自来水浸泡清洗并不能有效的降低样品的微生物指标，而用指标为pH2．5、ORP1180mV、ACC35mg／L的电生功能水处理鲜切果蔬产品，可以明显的降低附着于产品上的各类微生物。通过考察电生功能水浸泡处理对马铃薯切片表面色泽的影响，确认了电生功能水抑制其氧化褐变的效果，实验证明，电生功能水具有与常用褐变抑制剂L-半胱氨酸 柠檬酸等同的抗褐变效果。对提取到的马铃薯多酚氧化酶进行酶活钝化实验发现，电生功能水可以使马铃薯PPO活性降低50％以上，与L-半胱氨酸 柠檬酸对马铃薯PPO活性的抑制能力相当，说明电生功能水能有效的钝化果蔬组织中多酚氧化酶的活性而抑制果蔬切片氧化褐变的发生。试验结果证明：电生功能水处理可以有效杀灭附着于鲜切马铃薯表面的各种微生物，并可以较好的抑制鲜切马铃薯氧化褐变的发生，增加了产品的食用安全性，提高了产品的品质。     

Novel Browning Inhibitor Formulation for Fresh-cut Apples

ABSTRACT: Development of a browning inhibitor for fresh-cut apples that would not support human pathogen survival was investigated. Granny Smith and Fuji wedges were treated with acidic or neutral browning inhibitors with and without addition of sodium hexametaphosphate. Wedges in modified atmosphere packaging pouches were observed for browning during storage at 4 °C and 10 °C. A pH 2.9 dip containing ascorbic acid, citric acid, and sodium hexametaphosphate suppressed browning for at least 3 wk at 4 °C, whereas formulations without hexametaphosphate failed within 1 wk. These results demonstrate that browning in fresh-cut apples can be controlled with a formulation unlikely to support human pathogen survival or growth.     

不同浓度的没食子酸丙酯对鲜切生姜保鲜特性的影响

本文研究了没食子酸丙酯(PG)对鲜切生姜保鲜效果的影响。挑选新鲜,无病斑,无机械损伤,大小一致的生姜,清洗去皮,用不锈钢刀切分成5 mm厚薄片,分别采用0.10%、0.20%、0.30%没食子酸丙酯溶液浸泡处理,在14℃(±1.0℃)条件下贮藏。通过测定鲜切生姜的失重率、褐变度、可溶性固形物含量、Vc含量、丙二醛(MDA)含量、多酚氧化酶(PPO)活性、过氧化物酶(POD)活性、硬度、弹性以及咀嚼性的变化来研究PG对鲜切生姜保鲜效果的影响。结果表明:没食子酸丙酯溶液浸泡处理能够在不同程度上保持鲜切生姜的质地,降低鲜切生姜的失重率和MDA含量,延缓鲜切生姜的褐变,抑制PPO和POD的活性,同时使Vc、可溶性固形物含量和硬度维持在较高水平,而咀嚼性、弹性保持在较低的水平。其中,0.20%PG处理对鲜切生姜的保鲜效果最好。     

超高压处理对鲜杏鲍菇品质的影响

本文以新鲜杏鲍菇为研究对象,研究了超高压不同处理方式下(不同压力100 MPa、150 MPa、200 MPa、250 MPa、300MPa,不同保压时间3 min、6 min、9 min、12 min、15 min、18 min),对杏鲍菇多酚氧化酶(PPO)、失重率、色差、硬度、感官等品质的影响。研究结果表明,超高压处理后杏鲍菇的PPO酶活力和弹性随着压力的升高和保压时间的延长出现先下降后上升的变化,色差的亮度(L*)值和硬度则逐渐降低,黄度(b*)值和失重率则逐渐增加。在储藏期内(0~12 d),贮藏温度为4℃,超高压处理下(压力200 MPa保压时间9 min)的酶活力低于未处理的杏鲍菇样品,而高压处理的失重率增幅大于未处理组样品,而色差和硬度变化则小于未处理组样品。通过实验分析得到杏鲍菇超高压处理的最佳压力和保压时间参数为:200 MPa、9 min。     

紫外线照射与柠檬酸处理对鲜切苹果的保鲜作用

目的研究柠檬酸、紫外线照射、柠檬酸和紫外线照射联合处理对鲜切苹果生理生化的影响。方法以富士苹果为实验材料,分成4组,分别是0.5%柠檬酸(CA)溶液中浸泡5 min、紫外照射(UV)5 min/面、0.5%柠檬酸溶液中浸泡5 min+紫外照射(CA+UV)5 min/面、不处理的对照组(KB)。分别于0、1、3、5、7、10、13、15 d测定鲜切苹果的色差、多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)活性。结果富士苹果经过切分后,褐变严重。PPO、POD活性升高,PAL活性变化曲折,总体呈上升趋势。柠檬酸、紫外、柠檬酸和紫外联合处理的3三种处理方式都可以抑制鲜切苹果的褐变,降低PPO、POD、PAL的活性。在4种处理方法比较中,柠檬酸和紫外联合处理的效果比较好。结论柠檬酸和紫外联合处理是鲜切苹果的理想的保鲜方法。     

鲜切果蔬安全及质量控制研究进展

鲜切果蔬是近年来国际上流行的新型食品,具有新鲜、营养、方便、无公害等特点。本文根据鲜切果蔬的加工特性,研究了其在生产流程中的潜在危害,并对国内外有关鲜切果蔬质量安全的防控措施进行了综述。     

Quality of Fresh-cut Apple Slices as Affected by Low-dose Ionizing Radiation and Calcium Ascorbate Treatment

ABSTRACT: Although ionizing radiation effectively inactivates food-borne bacterial pathogens in fresh-cut fruits and vegetables, it may adversely affect product quality. In this study, the effects of calcium ascorbate (CaA) and ionizing radiation on quality of 'Gala' apple slices under modified atmosphere packaging were investigated. 'Gala' apple slices, treated with water or 7% CaA followed by either nonirradiation (0 kGy) or irradiation at 0.5 and 1.0 kGy, were stored at 10°C for up to 3 wk. The titratable acidity, pH, firmness, ascorbic acid content, color, and microflora population were measured weekly throughout storage. Irradiation did not affect titratable acidity and pH of sliced apples. Fruit slices softened during irradiation and storage, but this decrease in firmness during storage was reduced by the CaA treatment. Although the ascorbic acid content of apple slices treated with CaA decreased rapidly during storage, the ascorbic acid content was always higher in those treated samples than in the apple slices treated with water. Irradiation decreased both L * and hue values of apple slices. Hue values decreased during the entire storage period while L * increased during the 1st wk of storage, then decreased between 1 to 3 wk of storage. CaA increased L * and hue values of apple slices, suggesting CaA reduced browning, even in irradiated samples. The microflora population of apples slices was not affected by CaA, and CaA treatment did not alter the reduction in microflora by irradiation. The combination of CaA and irradiation enhanced microbial food safety while maintaining quality of fresh-cut apple slices.     

壳聚糖涂膜对鲜切马铃薯褐变程度的影响

研究了不同壳聚糖涂膜液对鲜切马铃薯色泽、褐变强度和多酚氧化酶活力的影响。结果表明:对于鲜切马铃薯的褐变程度,以复合涂膜液Ⅰ(1%壳聚糖+0.5%抗坏血酸)或以复合涂膜液Ⅱ(1%壳聚糖+0.5%抗坏血酸+0.15%氯化钙+0.8%乙二胺四乙酸二钠)抑制效果显著,且以后者更佳。     

Ascorbic acid and 4-hexylresorcinol effects on pear PPO and PPO catalyzed browning reaction

ABSTRACT:  The effects of ascorbic acid (AA) and 4-hexylresorcinol (4-HR) on pear polyphenoloxidase (PPO) activity and stability have been investigated in vitro . AA does not interact directly with PPO but prevents browning by reducing oxidized substrates. The 4-HR exerts a dual role on PPO. If no substrates are present, it interacts preferably with the deoxy form of PPO inactivating it. If substrates and 4-HR are both present they compete for the catalytic site. The 4-HR behaves then as a canonical enzyme inhibitor, binding to the met form of PPO. Simultaneous addition of 4-HR and AA has synergistic inhibition or inactivatory effects depending on the presence or the absence of PPO substrates.