Storage temperature and type of cut affect the biochemical and physiological characteristics of fresh-cut purple onions

Minimal processing of onion (Allium cepa L.) results in convenience and freshness in a single product. However, inappropriate storage of fresh-cut onion results in losses of nutritional and sensory characteristics. To further understand this phenomenon, we evaluated the effect of the storage temperature and type of cut on the quality of fresh-cut purple onions. Purple onions (cv. Crioula Roxa) were minimally processed using two types of cut (10 mm cubes and 3–5 mm thick slices) and stored at different temperatures (0, 5, 10 and 15 °C) with 85–90% relative humidity (RH) for 15 days. The following analyses were performed to evaluate the shelf life of the purple onion: pungency, total phenolic content, anthocyanin content, quercetin content, respiratory rate, color, soluble solids content, titratable acidity, pH, dryness and deterioration index (DDI), and decay index (DI). Fresh-cut onions stored at 0 °C showed less pungency, lower respiratory rate levels and less variation of total phenolic, anthocyanin and quercetin contents. In addition, the physicochemical aspects and appearance changed less with fresh-cut onions stored at 0 °C. Moreover, slicing enabled a higher stability of the physicochemical and biochemical aspects in comparison to dicing. Storage of slices at 0 °C allowed preservation for up to 15 days.     

鲜切苹果自发气调包装研究

以低密度聚乙烯、高密度聚乙烯、聚丙烯膜为包装材料,研究其对鲜切苹果的保鲜效果。结果表明:3种保鲜膜包装均能不同程度地抑制鲜切苹果呼吸强度,推迟呼吸高峰期到来,减少营养物质消耗,0.04mmLDPE保鲜膜较适合于鲜切苹果的自发气调包装。     

切分胡萝卜生理变化的研究

研究了胡萝卜切分后的生理变化规律。结果表明,鲜切胡萝卜的呼吸强度、白度值升高,pH值、总胡萝卜素含量下降。切分胡萝卜的硬度、渗出物含量以及颜色的变化与其切分表面的水分损失有着密切的关系,另外机械损伤也是造成鲜切胡萝卜脱色的直接因素。     

Discrimination of four different postharvest treatments of ‘Red Delicious’ apples based on their volatile organic compound (VOC) emissions during shelf-life measured by proton transfer reaction mass spectrometry (PTR-MS)

Storage methods extend the postharvest life of apples from weeks to up to one year; however, these methods also alter the production of volatile organic compounds (VOCs), which amongst others, are important for aroma attributes. While the impact of storage on particular aroma components has been established, high throughput methods for determining the storage history during shelf-life are elusive. Here we show the potential of proton transfer reaction-mass spectrometry (PTR-MS), an MS-based metabolic fingerprinting technique, for characterizing fruit in the postharvest chain. The VOC fingerprint of apples (Malus × domestica Borkh. ‘Red Delicious’) was analyzed by PTR-MS during four weeks of shelf-life ripening after storage under four different storage conditions: ULO (ultra-low oxygen), DCA-CF (dynamic controlled atmosphere monitored by chlorophyll fluorescence), RLOS (repeated low oxygen stress) and 1-MCP (1-methylcyclopropene) in ULO. PTR fingerprint mass spectra of the apple headspace, obtained in short time without sample preparation or preconcentration, were sufficient to discriminate the four storage conditions during shelf-life. Moreover, we were able to monitor the changes in quality-critical VOC classes, including esters and terpenes, during shelf-life and observe the differential impact of the storage history on these VOCs. This work emphasizes the potential of PTR-MS as a valuable addition to targeted GC–MS-based approaches in postharvest research.     

光对储存期辣椒果实辣椒素含量的影响

采用湘研4号(中等辣度)和景尖椒3号(高辣度)两个辣椒品种的青熟果实,以有光和无光两种不同的条件于室温下储存,就储存期辣椒果实中辣椒素含量的变化进行研究。发现有光储存利于果皮中辣椒素含量的增加,无光储存利于胎座中辣椒素含量的增加。     

Ethanol vapor and saprophytic yeast treatments reduce decay and maintain quality of intact and fresh-cut sweet cherries

The objective of this study was to evaluate the use of an ethanol vapor release pad and a saprophytic yeast Cryptococcus infirmo-miniatum (CIM) to reduce decay and maintain postharvest quality of intact or fresh-cut sweet cherries (Prunus avium) cv. Lapins and Bing. Intact or fresh-cut fruit were packed in perforated clamshells (capacity 454 g) and stored at 1, 10 or 20 °C for up to 21, 14 and 8 d, respectively. For ethanol treatment, a pad made with silica gel powder containing 10 g ethanol and covered with perforated film, which allows ethanol vapor to diffuse gradually, was attached to the upper lid of the clamshells. Ethanol treatment caused accumulation of ethanol in the packaging headspace, about 10 μL L⁻¹ with little change within 14 d at 1 °C, 23 μL L⁻¹ at d 1 and decreased to 15 μL L⁻¹ at d 10 at 10 °C, and 26 μL L⁻¹ at d 1 and decreased to 13 μL L⁻¹ at d 3 at 20 °C. Ethanol content in fruit was less than 9 mg kg⁻¹ in all the control fruit, and increased to 16, 34 and 43 mg kg⁻¹ in ethanol-treated fruit at 1, 10 and 20 °C, respectively. Nonetheless, a sensory taste panel did not perceive any flavor difference from the ethanol treatment. The ethanol treatment retarded softening, darkening, and acid decrease in fruit as well as discoloration of the stems, and extended shelf-life of intact cherries. Ethanol reduced brown rot (Monilinia fructicola) in fresh-cut cherries stored at 20 °C, but not at 1 and 10 °C. A pre-packaging dip in CIM completely controlled brown rot in inoculated fresh-cut cherries stored at 1 °C, and in naturally infected cherries at 20 °C.     

Advances in QTL mapping for ethylene production in apple (Malus × domestica Borkh.)

Ethylene is a gaseous hormone that coordinates several important physiological processes resulting in the final fruit quality in apple. Due to its genetic heterozygousity, apple offers the possibility to exploit the natural allelic variation existing at the level of two genes involved in the ethylene biosynthetic pathway, Md-ACS1 and Md-ACO1. The allelism of these two genes can be exploited for the advanced selection of genotypes characterized by low ethylene production, with a consequent extended postharvest storability. The impact of these two elements in ethylene control was verified using two specific apple populations (‘GDxBr’ and ‘FjxMG’) presenting distinct allelotype configurations. In the first progeny, two QTLs were identified in genetic positions corresponding with these genes, and for the first time the association of a QTL for ethylene production with Md-ACO1 in apple was established. However, the analysis carried out on the second population, homozygous for the allele of Md-ACS1 associated with a low ethylene production, suggested the possible involvement of other genetic elements in the regulation of ethylene production. In the end we also present, in parallel to the GC assessment, a novel methodology based on proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) for a more reliable, fast and efficient monitoring of the ethylene production in apple.     

超高压处理对鲜切山药片质量的影响

为研究适宜的鲜切山药片的保藏方法,采用超高压处理对鲜切山药片进行保鲜。将鲜切山药片分别采用0MPa、200MPa、400MPa和600MPa加压处理10min后,在4℃条件下贮藏9d,分析超高压处理对贮藏期间鲜切山药片中细菌总数、多酚氧化酶活性、褐变指数、可溶性固形物、总酸和维生素C含量的影响。结果表明：600MPa压力处理10min后,可抑制于褐变相关的多酚氧化酶,抑制微生物生长,产品在4℃条件下贮藏9d后,仍然可具有较好的理化指标,表明该法是一种较好的鲜切山药片的保藏方法。     

Effect of antioxidants in controlling enzymatic browning of minimally processed persimmon ‘Rojo Brillante’

‘Rojo Brillante’ is an important variety of persimmon that after removal of the astringency with high levels of CO₂, maintains firmness and sweetness, making possible its commercialization as a fresh-cut commodity. However, the commercial success of the product is limited mainly by enzymatic browning. This work presents the effect of a wide range of antioxidants on enzymatic browning of ‘Rojo Brillante’ persimmon combining in vitro (extracts and precipitates) and in vivo (cut tissue) studies. Preliminary screening of the antioxidants, determined by absorbance and color measurements of persimmon extracts and pellets, showed that 4-hexylresorcinol (Hexyl), citric acid (CA) and calcium chloride (CaCl₂) were effective at controlling browning at 10 mM; whereas, ascorbic acid (AA) required a higher concentration (25 mM). Peracetic acid, cyclodextrin, cysteine, and hexametaphosphate were not effective at controlling browning, even at a concentration of 50 mM. In in vivo studies, AA (1.12%) and CA (0.21%) were the most effective treatments to control enzymatic browning of fresh-cut material, reaching the limit of marketability in 5–7 days, whereas, Hexyl and CaCl₂ did not reach 1 day of storage. The results showed that optimum concentrations in cut tissue did not always correlate with the in vitro studies, indicating that antioxidants have an effect not only in browning reactions, but also in metabolic activity and cell wall changes during wound-induced reactions. The results provide relevant information for further development of minimally processed ‘Rojo Brillante’ persimmon during storage at 5 °C.     

鲜切莲藕微生物模型的建立及货架寿命预测

研究鲜切莲藕在不同贮藏温度下细菌生长趋势和感官质量的变化,建立微生物生长模型,预测鲜切莲藕的货架寿命;将莲藕切片经保鲜处理、包装后,置4、8和20℃贮藏温度下贮藏,测定贮藏期间鲜切莲藕中细菌总数,利用DPS软件,建立Gompertz模型;结果表明,试验中所建立的Gompertz模型能有效地拟合在不同贮藏温度下鲜切莲藕中细菌总数的动态变化;建立的微生物模型能预测不同贮藏温度下、不同贮藏时间内鲜切莲藕中的细菌总数,为快速、有效地评估鲜切莲藕的货架寿命和微生物安全性,提供了一个方便有效的方法。