Superoxide Dismutase Activities in Senescing Apple Fruit (Malus domestica Borkh.)

Total superoxide dismutase (SOD:superoxide: superoxide oxidoreductase; EC 1.15.1.1) activity and individual activities of its three different metalloenzymes, CuZn-SOD, Fe-SOD, and Mn-SOD, were investigated during senescence of apples (Malus domestica Borkh.). Total SOD activity and relative activities of its three forms varied greatly among cultivars. Activities underwent considerable change during senescence of fruit, but changes were different among cultivars. Whether fruit senesced at 0°C or 20°C had little effect on SOD activities, and application of the antioxidant diphenylamine (DPA) did not alter activities. SOD activities increased with occurrence of the physiological disorder “senescent breakdown,” but did not increase with occurrence of the disorder “superficial scald.” In a given apple cultivar, changes in total SOD activity generally paralleled activities of the different SOD forms. Such activity may reflect changes affecting food and nutritive quality of the fruit.     

基于气相离子迁移谱技术分析延安市不同县区的富士苹果挥发性成分的差异

目的 分析比较延安市不同区县富士苹果之间挥发性成分的差异。方法 采用气相离子迁移谱(gas chromatography-ion mobility spectrometry,GC-IMS)技术对延安市13个县区的晚熟富士苹果的挥发性成分进行分析,建立富士苹果的挥发性成分特征指纹图谱,并进行主成分法和聚类分析法分析。结果 在延安市13个县区富士苹果样品中共鉴别出的挥发性成分54种,主要有酯类、醇类、酮类、醛类和酸类等物质,各县区富士苹果的酯类和醇类物质占比较高,分别占总挥发性成分的48.98%~53.19%和13.04%~19.23%。13个县区富士苹果共有的挥发性成分有2-乙基呋喃、丙酸乙酯、甲酸异戊酯、乙酸己酯、乙酸异戊酯、2-甲基丁基乙酸酯等,这些物质共同奠定了延安富士苹果香气的总体基调,各县区富士苹果的挥发性成分的具体种类和含量各有不同。结论 本研究通过建立挥发性成分特征指纹图谱,明确了延安市不同区县富士苹果之间挥发性成分存在的差异。研究发现延安市宝塔区的富士苹果挥发性成分种类及含量较丰富,其特征性物质有巴豆酸乙酯、异丙醇、2,3-丁二酮、乙酸甲酯等。黄陵县富士苹果特有丁酸丙酯、丁酸甲酯等物质。宜川县富士苹果的特征性物质有反式-2-已烯醛、丁酸异戊酯、丁酸等。此外富县富士苹果中含量丰富的挥发性成与黄陵县富士苹果的部分挥发性成分一致。延川、洛川县、甘泉县、黄龙县和吴起县的富士苹果中含量丰富的挥发性成分较为相似;子长市、安塞区、志丹县、延长县的富士苹果中含量丰富的挥发性成分较为相似。结果表明GC-IMS技术在延安市富士苹果的挥发性成分的分析方面具有较好的应用价值,可用于不同县区富士苹果的风味识别和品质评价。     

Electromyography of Eating Apples: Influences of Cooking, Cutting, and Peeling

ABSTRACT: The mastication of 7 differently prepared apple samples (raw pieces peeled and unpeeled, sliced, grated, cooked pieces with and without peel, and half-cooked pieces, 10 g each) was evaluated using electromyography (EMG). Eleven subjects participated in the EMG recording of both sides of the masseter and temporal muscles while eating samples normally. Only the grated sample reduced the number of chewing strokes and muscle activity before swallowing. In contrast, the thin apple slices produced significantly shorter contraction duration and cycle time only during the 1st 5 chewing strokes. The EMG duration and cycle in subsequent chews, as well as the other parameters, did not significantly differ between slices and pieces. Cooked apples exhibited significantly lower EMG amplitude and muscle activity per chew than their raw counterparts; however, there was no evidence of reduced total muscle activity required for swallowing. Raw and cooked apples with peel yielded significantly greater EMG amplitude and longer duration than those without peel. These findings suggest that appropriate preparation is necessary for people with various mastication abilities: grated for very low ability, cooked for those with weak chewing force, and unpeeled for mastication training.     

Efficacy of thyme oil-alginate-based coating in reducing foodborne pathogens on fresh-cut apples

In this study, the inhibition of an alginate-based edible coating (EC) containing thyme oil (0.05%, 0.35% and 0.65%) was evaluated against Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus and Escherichia coli O157:H7 inoculated onto fresh-cut apples. To investigate the antibacterial mechanism of thyme oil, the constituent compounds of that were analysed by gas chromatography-mass spectrometry (GC-MS), and the cellular damage of pathogens was observed by scanning electron microscopy (SEM). Results showed that alginate-based EC containing thyme oil effectively inhibited the growth of pathogens on fresh-cut apples. GC-MS analysis revealed thymol (47.23%) as the major compounds in thyme oil. SEM showed that the cell membrane of foodborne pathogens was damaged by thyme oil, causing their inactivation. Treatment with alginate-based EC containing 0.05% thyme oil preserved the sensory characteristics of fresh-cut apples. Therefore, using alginate-based EC with thyme oil may represent a potential approach to preserve and enhance the safety of fresh-cut apples.     

苹果中阿维菌素的残留分析与消解动态研究

目的探究12.5%阿维·哒螨灵(0.25%阿维菌素+12.25%哒螨灵)可湿性粉剂成分之一阿维菌素在苹果和土壤中的残留及消解动态。方法分别在北京、安徽、陕西3地种植的苹果和土壤中进行阿维菌素最终残留实验及消解动态实验。样品经乙腈提取、盐析、浓缩处理后,采用高效液相色谱-荧光法检测阿维菌素的残留量。结果该方法检出限为0.02ng,定量限为0.001mg/kg,在苹果和土壤中的添加回收率分别为88.7%~94.2%和90.5%~96.4%,相对标准偏差分别为3.56%~6.01%和3.43%~7.25%。阿维菌素在苹果和土壤中的半衰期分别为2.6~4.4 d和3.4~6.2 d。在推荐使用高剂量和推荐使用高剂量1.5倍的情况下,施药后7、14、21、28 d阿维菌素在苹果上的残留量均小于MRL值0.02 mg/kg。结论 12.5%阿维·哒螨灵可湿性粉剂其之一成分阿维菌素在苹果上的安全间隔期可建议定为7 d。     

QuEChERS-气相色谱质谱法测定苹果中45种农药残留

建立了QuEChERS-气相色谱质谱法同时测定苹果中45种农药残留检测方法,样品以1%乙酸乙腈提取,经25 mg PSA、25 mg C₁₈和7.5 mg GCB净化,GC-MS选择离子监测(SIM)模式下检测,基质匹配外标法定量。检测结果表明,45种农药在10~200 μg/L质量浓度范围内线性关系良好,各农药的线性相关系数均大于0.995;在30、50和100 μg/kg添加水平下,45种农药的回收率在69.3%~116%之间,相对标准偏差在0.7%~7.9%之间;方法的检出限在1.5~15.0 μg/kg之间,定量限在5.0~50.0 μg/kg之间。该方法准确度高、精密度好、步骤简单、操作快捷、成本低廉,适用于苹果中农药残留的检测。     

Using polysaccharide-based edible coatings to maintain quality of fresh-cut Fuji apples

The effect of alginate and gellan-based edible coatings on the shelf-life of fresh-cut Fuji apples packed in trays with a plastic film of a known permeability to oxygen (110 cm³ O₂ m⁻² bar⁻¹ day⁻¹) was investigated by measuring changes in headspace atmosphere, color, firmness and microbial growth during 23 days of storage at 4 °C. Concentration of O₂ and CO₂ in the package was measured and no significant differences between coated and uncoated fresh-cut apples were observed. Ethylene concentration in coated apples seemed to be delayed since it remained below 50 μl l⁻¹ throughout the whole refrigerated storage period, while production of this gas was detected in uncoated apples from the very initial days of storage. Coated apple wedges exhibited ethanol and acetaldehyde formation from the second week of storage indicating fermentative metabolism. Polymers were crosslinked with a calcium chloride solution, to which the antibrowning agent N-acetylcysteine was added, being incorporated into the coatings formulation and helping to maintain firmness and color of apple wedges during the entire storage time. The application of the edible coatings also retarded the microbiological deterioration of fresh-cut apples. Alginate and gellan edible coatings effectively prolonged the shelf-life of Fuji apple wedges by 2 weeks of storage compared with the control apple slices which showed a considerable cut surface browning and tissue softening from the very early days of storage, limiting their shelf-life to less than 4 days.     

寒地特色中小苹果果汁加工酶处理技术研究

以黑龙江省中小型苹果K9、铃铛、黄太平、金红品种为试材,以品种、酶解时间、酶解温度、加酶量作四因素四水平的正交实验,研究适宜加工果汁的苹果品种及酶解工艺。结果表明:品种选择K9,酶解时间4h,酶解温度50℃,加酶量为800U/100g组合的果汁质量指标最佳。此工艺条件下可使出汁率提高41%,可溶性固形物提高9%,总酸提高32%,色值降低82%。其中,影响各项质量指标的主要因素是品种,其次是酶解温度。     

外源一氧化氮对苹果采后黑斑病的控制

在离体条件下研究了NO供体硝普钠(sodium nitroprusside,SNP)对苹果黑斑病菌互隔交链孢(Alternaria alternata)生长、菌落形态及其超微结构的影响,并在体内条件下研究了其对苹果黑斑病的治愈作用。结果表明SNP处理能显著的抑制A.alternata的孢子萌发和菌丝生长,存在浓度依赖效应,当浓度为1 g/100 m L SNP,与对照相比,其对菌丝生长和孢子萌发的抑制率分别达到70%和75.9%;扫描电镜和透射电镜观察发现SNP处理的A.alternata菌丝表面粗糙,粗细不均匀,部分出现塌陷;孢子细胞受到不同程度的破坏,细胞膜发生破裂。同时发现外源SNP处理对损伤接种的苹果黑斑病具有治愈作用,其中0.5 g/100 m L SNP处理效果最佳。可见外源NO作为代替化学合成药物的防腐剂在采后病害控制中具有潜在的应用前景。      

A profile of physicochemical and antioxidant changes during fruit growth for the utilisation of unripe apples

The physicochemicals associated with fruit quality, antioxidant activities and changes in polyphenol composition during Fuji apple growth were investigated from the 25th to 105th day after full bloom day (DAFB). Three kinds of antioxidant assays, including oxygen radical absorbing capacity (ORAC) were executed, and polyphenol composition were examined using HPLC. The change in weight of the Fuji apples during fruit growth showed a typical sigmoidal curve. Both the rise of the soluble solid content and the drop of the titratable acidity appeared to be more significant (p < 0.05) after the 85th DAFB. Concurrently, the antioxidant activities and the polyphenol content decreased (p < 0.05) rapidly after the same date. Accordingly, a profitable thinning date can be chosen around the 85th DAFB to utilise dropped unripe apples as resources of antioxidants. Furthermore, the antioxidant activities of Fuji apples may be highly affected by the chlorogenic acid content.