Avocado Fruit Quality Management during the Postharvest Supply Chain

Avocados are a popular subtropical fruit of high economic importance, and the European Union is the biggest importer of the bulk of the fruit coming from countries such as South Africa, Chile, and Israel. The fruit is highly nutritious, being rich in vitamins A, B, C, minerals, potassium, phosphorus, magnesium, iron, and antioxidants. The biggest challenge is that the fruit is highly susceptible to qualitative and quantitative postharvest losses. Successful maintenance of avocado fruit quality during the supply chain depends on many aspects, including adequate orchard management practices, harvesting practices, packing operations, postharvest treatments, temperature management, transportation and storage conditions, and ripening at destination. Postharvest losses are mostly attributed to flesh softening, decay, physiological disorders, and improper temperature management. Management of the supply chain is solely done to provide the fruit with the most favorable conditions to extend storage life, and retain quality and nutritional attributes of the fruit. The focus of this review is therefore to study the findings that have emanated from research done to retain overall avocado fruit quality and to reduce postharvest losses during the supply chain through the adoption of appropriate and novel postharvest technologies.     

Effect of Calcium Salts on Susceptibility to Browning of Avocado Fruit

Fuerte avocados were dipped in 0.18M solutions of calcium chloride (CaCl₂·6H₂O) or calcium phosphate (CaHPO₄) or calcium arsenate [Cas(AsO₄)₂] or calcium nitrate [Ca(NO₃)₂·4H₂O] to determine whether these treatments had any effect on the browning components in avocados. It was found that calcium treatments suppressed both respiration and polyphenol oxidation and also reduced the content of total phenolics, leuco-anthocyanins, and flavonols. Of those calcium treatments used, calcium arsenate gave the best results.     

1-甲基环丙烯处理延迟采后油梨果实后熟的研究

以“哈斯”油梨果实为试材,在20℃和相对湿度85%~90%的条件下,研究了20、40、60、80nL/L的1-甲基环丙烯(1-MCP)对果实的乙烯释放量、硬度、褐变指数、多聚半乳糖醛酸酶(PG)、多酚氧化酶(PPO)和纤维素酶活性的影响。结果表明,与对照相比,1-MCP可以明显降低果实的乙烯释放量,使果实乙烯峰值约推迟8~10d出现;在处理后的10d内,1-MCP能有效保持果实的颜色;1-MCP能有效抑制PPO、纤维素酶的活性,并推迟多聚半乳糖醛酸酶活性高峰出现的时间。     

茶多酚对油梨果实保鲜效果的评价

为探明茶多酚对油梨采后贮藏期间品质和生理变化的影响。以国内油梨品种桂研10号为试材,研究了不同浓度茶多酚对油梨贮藏期间营养品质和抗氧化酶的变化。结果表明,2.0%茶多酚处理可有效延长油梨的保鲜期,贮藏12 d后,2.0%茶多酚处理油梨腐烂率为14.86%,比CK低81.90%;贮藏20 d后,2.0%茶多酚处理的油梨失重率为10.46%,硬度为2.9 kg/cm²,可溶性固形物含量7.45%,维生素C含量42.88 mg/100 g,可溶性蛋白含量6.52 mg/g,保持油梨果实硬度和重量,控制溶性固形物、维生素C、可溶性蛋白的下降,促进超氧化物歧化酶（SOD）、过氧化物酶（POD）的活性,降低腐烂率,有效延长了保鲜时间,同时保持了良好的营养品质。综上所述,2.0%茶多酚处理对油梨的保鲜效果最好,是一种安全、高效、低成本油梨保鲜药剂。     

Isolation and Characterization of Invertase from Iraqi Date Fruit

Soluble invertase was isolated and characterized from the pericarp of Iraqi date fruit, Sayer variety. The optimum pH of the soluble invertase was 4.0–4.7 and the optimum temperature was 50°C. The specific activity of the partially purified soluble invertase was 70.0 units per mg protein. The molecular weight of the soluble invertase was 70.0 units per mg protein. The molecular weight of the soluble invertase was probably more than 300,000 Daltons, and had high affinity for sucrose with a Km value of 3.33 × 10^-3 mM. Sodium dodecyl sulfate (SDS) inhibited the activity of the soluble invertase.     

Isolation and Characterization of Pectin Methylesterase from Apple Fruit

Two forms of the enzyme pectin methylesterase are evidenced in the apple (Malus communis). They differ both in their charge and molecular weight. The two enzymes were separated by DEAE-cellulose chromatography. Their molecular weights, determined by gel-filtration, were 55000 and 28000 daltons. The heavier form has been purified at homogeneity and subjected to investigations regarding its activity as a function of the pH and temperature, and determination of its kinetic parameters. The enzyme has a Km value of 1.05 mg/mL for citrus pectin and an optimum activity in the pH range between 6.5-7.5. The enzyme was stable up to 40°C. Incubation for 1 min at 90°C leads to its complete inactivation.     

1- 甲基环丙烯、乙烯利和壳聚糖涂膜处理对油梨完熟天数及腐烂的影响

以油梨果实为原料,以不同浓度的1- 甲基环丙烯 (1-MCP)、乙烯利和壳聚糖涂膜处理对油梨果实的完熟天数和腐烂程度进行了研究。实验结果表明,贮藏在常温条件下 (25～35℃,平均相对湿度85%)的油梨果实其后熟时间的长短与1-MCP 的浓度相关,且随着1-MCP 浓度的提高,果实的后熟时间延长;壳聚糖涂膜处理可显著降低油梨果实的腐烂程度。壳聚糖涂膜的时间越早,防腐的效果越好;1-MCP 处理的浓度高于100nl/L 的情况下,壳聚糖的防腐作用更加明显;对于仅用乙烯利催熟的油梨果实没有必要进行壳聚糖涂膜处理。乙烯利处理3d 后也没有必要用1-MCP 和壳聚糖处理。     

Isolation of Nanocellulose from Pomelo Fruit Fibers by Chemical Treatments

This study aims to isolate cellulose nanofibers from locally abundant pomelo fruit. The peels were subjected to alkali treatment (NaOH) with different concentrations and soaking times. Acid hydrolysis was also carried out to obtain an aqueous suspension of nanocellulose. The treated cellulose fibers were characterized by various methods. Alkali treatment was able to remove noncellulosic constituents. Microscopy techniques yielded morphology of elementary fibers with a compact structure with both micro- and nano-scaled fibers. An improved onset of degradation was likely caused by an increase in crystallinity evidenced by X-ray diffractometry (XRD). Acid hydrolysis could successfully individualize cellulose nanofibers as observed by transmission electron microscopy (TEM).     

沙棘果原花青素的分离纯化研究

用大孔树脂、Sephadex LH-20凝胶色谱的方法和反相高效液相色谱分离纯化沙棘果中的原花青素。结果表明：大孔树脂层析法分离纯化沙棘果中的原花青素时使用50％的乙醇水溶液洗脱得到的洗脱液中原花青素的含量较高，达71．9％；将经过大孔树脂层析分离纯化的原花青素粗品经Sephadex LH-20柱分离，50％乙醇作为流动相，原花青素粗品可纯化至95％以上。反相高效液相色谱分析发现，从Sephadex LH-20洗脱下来的组分中含有原花青素的二聚体。     

Characterization of Starch Isolated from Avocado Seeds

Starch granules of avocado seeds were oval shaped with a relatively smooth surface and an average diameter of 5–35μ. The starch was nonionic and not waxy. The gelatinization temperature range of the starch was 62–75°C. Brabender viscosity curves showed that the starch had restricted swelling with no pronounced pasting peak but with good pasting stability and average set back on cooling. Avocado seed starch exhibited type B x-ray diffraction pattern.     

枸杞子阿拉伯聚糖的提纯分离及其构造特征研究

对枸札子水溶性粗多糖进行了分离提纯和化学构造研究。除了已经报道过的4种糖蛋白AGP（Arabinogalactan-protein:Cp-1-C,Cp-1-D,Cp-2-B和Hp-2-C)外，还得到了一种均一的阿拉伯聚糖（Hp-0-A,分子量23，000），运用甲基化分析及其NMR技术确定了其主要构造特征。     

Isolation and Identification of Lactic Acid Bacteria from Fermented Red Dragon Fruit Juices

Abstract: Red dragon fruit or red pitaya is rich in potassium, fiber, and antioxidants. Its nutritional properties and unique flesh color have made it an attractive raw material of various types of food products and beverages including fermented beverages or enzyme drinks. In this study, phenotypic and genotypic methods were used to confirm the identity of lactic acid bacteria (LAB) appeared in fermented red dragon fruit (Hylocereus polyrhizus) beverages. A total of 21 isolates of LAB were isolated and characterized. They belonged to the genus of Enterococcus based on their biochemical characteristics. The isolates can be clustered into two groups by using the randomly amplified polymorphic DNA method. Nucleotide sequencing and restriction fragment length polymorphism of the 16S rRNA region suggested that they were either Enterococcus faecalis or Enterococcus durans. Practical Application: Current research revealed the use of biochemical analyses and molecular approaches to identify the microbial population particularly lactic acid bacteria from fermented red dragon fruit juices.     

沙棘多糖分离纯化及抗氧化活性

分离纯化沙棘多糖(sea buckthorn(Hippophae rhamnoides)polysaccharides,SBP),并对其单糖组分、结构表征及体外抗氧化活性进行分析.通过水提醇沉、Sevag法除蛋白得到沙棘粗多糖,利用DEAE-52纤维素柱对其进行分离纯化得到中性多糖SBP-I和酸性多糖SBP-II、SB...     

1-MCP结合壳聚糖涂膜延迟油梨果实后熟的研究

研究了壳聚糖、1-甲基环丙烯(1-MCP)及其复合处理对采后"哈斯"油梨果实后熟的影响.油梨果实先用1-MCP处理24 h,再用2.0% CTS水溶液处理,然后贮存在20℃、85%～90%相对湿度下后熟,在此期间取样分析乙烯释放量、硬度、失重、色度指数、多聚半糖醛酸酶(PG)和多酚氧化酶(PPO)的活性.结果表明:与对照相比,以100nL/L的1-MCP处理24 h和20 g/L的壳聚糖涂膜处理可以明显降低果实的乙烯、CO2释放量,并延迟果实呼吸高峰的出现,减少质量损失,推迟硬度下降,延缓果皮颜色的变化,同时抑制PG和PPO的活性.1-MCP处理结合壳聚糖涂膜延迟油梨果实后熟的效果更明显,果实的后熟时间约延迟12 d.以上结果说明两者结合处理能有效地延迟油梨果实的后熟.     

酒曲中酵母菌的分离鉴定及果酒发酵的初步研究

酵母菌是决定果酒品质的关键因素。采用稀释涂布平板法分离纯化酒曲中的菌株,以传统形态学及分子系统发育分析对酵母菌进行初步鉴定,从6种市售酒曲样品中分离出10株酵母菌,经 26S rDNA 序列分析,有3株为库德里亚夫毕赤酵母(Pichia kudriavzevii),1株为异常毕赤酵母(Pichia anomala),2株克鲁维酵母(Kluyveromyces marxianus),3株酿酒酵母(Saccharomyces cerevisiae),1株葡萄牙棒孢酵母(Clavispora lusitaniae)。通过初筛将筛选出的酵母菌CK-03用于猕猴桃汁发酵,发酵液经顶空固相微萃取-气质联用技术(solid phase microextractiongas chromatography/mass spectrometry,SPME-GC/MS)测定分析,结果显示共检测出25种挥发性成分,主要为酯类和醇类物质。     

百香果籽内生细菌的分离鉴定及生长条件的研究

百香果籽提取物具有多种生物学活性,其活性物质可能来源于内生菌的代谢产物,该文对柳州百香果果籽中的内生细菌进行分离和鉴定。以新鲜的百香果为原料,用平板计数琼脂(plate count agar,PCA)培养基分离纯化果籽中的内生细菌,然后对其进行分子生物学鉴定,最后测定其最适生长温度、最适pH值、生长曲线等生物学特征;结果显示利用PCA培养基从百香果果籽中分离到的内生细菌菌落均呈白色;经革兰氏染色,均为革兰氏阳性球菌,直径在1.3μm^1.9μm之间;随机挑选3株菌进行分子生物学鉴,均属于不动杆菌属;测定其生长条件,均在LB培养基中生长较好;最适生长pH值均为7.0;最适生长温度均为25℃,而在15℃以下和40℃以上时其生长收到较强的抑制;用LB培养基测定其生长曲线,菌株在接种后的6 h^16 h处于对数期。通过对百香果果籽中内生菌的分离鉴定,发现柳州百香果果籽中存在不动杆菌属细菌。     

皱皮木瓜腐败微生物的分离鉴定

为探明皱皮木瓜贮藏保鲜过程中腐败变质的原因,采用组织分离法对引起皱皮木瓜腐败的微生物进行分离纯化,初步分离出2株细菌和6株霉菌,未分离出酵母菌.回接实验结果表明共有2株细菌、3株霉菌能引起皱皮木瓜腐败.通过形态学及分子生物学对5株腐败微生物进行鉴定,结果表明:2株细菌分别为巨大芽孢杆菌(Bacillus megater...     

李果实贮藏期间4 株病原真菌的分离、鉴定及 碳源代谢指纹图谱分析

从采后贮藏过程中发病的“安哥诺”(Prunus angeleno)和“黑琥珀”(Prunus salicina cv. Black amber) 李果实中分离到4株丝状病原真菌。通过对病原菌株形态学特征观察以及核糖体rDNA ITS序列系统分析,确定菌株059#为串珠状赤霉(Gibberella moniliformis)、菌株067#为链格孢菌(Alternaria alternata)、菌株087#为草酸青霉(Penicillium oxalicum)以及菌株088#为塔宾曲霉(Aspergillus tubingensis)。进一步利用Biolog FF MicroPlate分析病原菌对95种碳源的利用能力,结果表明这4种病原菌的最适碳源皆在77种以上,且共同的最适碳源包括D-果糖、D-葡萄糖、蔗糖、山梨糖醇、苹果酸和柠檬酸等45种。     

桑椹采后致腐真菌的分离鉴定及其内生酵母保鲜效果

从腐烂桑椹中分离致腐真菌,通过形态学观察及内转录间隔区（internal transcribed spacer,ITS）序列分析进行种属鉴定,初步研究桑椹内生酵母对桑椹致腐真菌的体内外拮抗效果。结果表明,从腐烂桑椹中分离得到3 株真菌,分别鉴定为链格孢菌（Alternaria alternata）、黑曲霉（Aspergillus niger）和富克尔核盘菌（Botryotinia fuckeliana）,它们对桑椹均有致腐性。体外拮抗实验显示,拟粉红锁掷孢酵母对链格孢菌（Alternaria alternata） 和富克尔核盘菌（Botryotinia fuckeliana）具有较好的抑制活性;葡萄汁有孢汉逊酵母和异常威克汉姆酵母对3 种致腐真菌具有较好的抑制活性。体内拮抗实验表明,拟粉红锁掷孢酵母和葡萄汁有孢汉逊酵母对桑椹具有较好的保鲜作用。     

山楂果原花青素的微胶囊化研究

研究了山楂果原花青素的微胶囊化工艺,以提高其稳定性。结果表明:以麦芽糊精、阿拉伯胶为复合壁材的微胶囊化效果最佳;通过单因素和正交试验确定微胶囊化工艺为,微胶囊化温度30℃,微胶囊化时间1h,芯壁材质量比为3∶7,复合壁材阿拉伯胶质量分数为40%,螯合剂EDTA-2Na添加量占芯材和壁材总质量的0.02%,总固形物含量为250g/L。在此微胶囊化工艺下喷雾干燥所得产品的微胶囊化效率为95.9%,微胶囊产率为90.6%。通过高效液相色谱(HPLC)检测,山楂果原花青素微胶囊化前后主要成分未发生改变,且稳定性得以提高。