渐进式分级气调：增加“duke”蓝莓储存期的新颖方法
Graduated Controlled Atmosphere: A Novel Approach to Increase “Duke” Blueberry Storage LifeNatalia Falagán, Tiana Miclo，Leon A. Terry* Plant Science Laboratory, Cranfield University, Cranfield, United Kingdom
Blueberries (Vaccinium corymbosum L.) are highly valued for their health-promoting potential, yet they are extremely perishable. Controlled atmosphere (CA) strategies reduce blueberry respiratory metabolism, slowing down senescence. However, the sudden change of atmosphere could elicit a physical abiotic stress in the fruit, negatively affecting quality. We propose an innovative approach based on controlled graduation to slowly reach optimum gas storage conditions as an alternative to standard CA. For two consecutive seasons, “Duke” blueberries were subjected to four different storage conditions: control (air); standard CA (sudden exposure to 5 kPa O2 and 10 kPa CO2 across the experiment); GCA3 and GCA7 (gradually reaching 5 kPa O2 and 10 kPa CO2 in 3 and 7 days, respectively). Fruit were stored for 28 days at 0 ± 0.5°C. Real-time respirometry provided an in-depth insight to the respiratory response of blueberries to their gas environment. Blueberries subjected to the graduated application of CA (GCA) treatments had a lower steady-state respiration rate compared to control and standard CA fruit. This indicated a reduction in metabolic activity that positively impacted quality and storage life extension. For example, GCA3 and GCA7 blueberries had a 25% longer storage life when compared to control, based on reduced decay incidence. In addition, GCA fruit were 27% firmer than control and CA fruit after 28 days of cold storage. GCA3 had a positive effect on maintaining individual sugars concentrations throughout the experiment, and both GCA treatments maintained ascorbic acid content close to initial values compared to a decrease of 44% in the control fruit at the end of the experiment. This work provides a paradigm shift in how CA could be applied and a better understanding of blueberry physiology and postharvest behavior.
蓝莓（Vaccinium corymbosum L.）因其促进健康的潜力而受到高度重视，但它们极易腐烂。控制大气（CA）策略减少蓝莓呼吸代谢，减缓衰老。然而，大气的突然变化会引起果实的物理非生物胁迫，对果实品质产生负面影响。我们提出了一种基于控制分级的创新方法，以缓慢达到气体储存条件，作为标准CA的替代。连续两个季节，“杜克”蓝莓经受四种不同的储存条件：对照（空气）；标准CA（整个实验中突然暴露于5 kPaO2和10 kPaCO2）；GCA3和GCA7（分别在3天和7天内逐渐达到5 kPaO2和10 kPaCO2）。果实在0±0.5℃下贮藏28天。实时呼吸测定法可深入了解蓝莓对气体环境的呼吸反应。分级施用CA（GCA）处理的蓝莓，其稳态呼吸速率低于对照和标准CA果实。这表明代谢活性的降低对质量和贮藏寿命的延长产生了积极的影响。例如，与对照相比，GCA3和GCA7蓝莓的贮藏期延长了25%，这是基于减少了腐烂的发生率。冷藏28天后，GCA果实硬度比对照和CA果实硬度高27%。GCA3在整个试验过程中对维持单糖浓度有积极作用，两种GCA处理都将抗坏血酸含量维持在接近初始值的水平，相比之下，试验结束时对照果实的抗坏血酸含量下降了44%。这项工作为CA的应用提供了一种范式转换，也为蓝莓生理学和采后行为的研究提供了更好的理解。 Introduction Blueberries (Vaccinium spp.) have become a popular soft fruit because of their organoleptic characteristics and health-promoting compound content (Manganaris et al., 2014). Yet, blueberries are highly perishable. Their storage life at 0°C varies between 14 and 20 days depending on preharvest factors (i.e., cr, ripeness stage, harvest method) and storage conditions (Matiacevich et al., 2013). Slowing down respiration, the main process in fruit metabolism (Gomes et al., 2010), is key to delaying senescence. Respiration is mostly affected by temperature and the respiratory gaseous environment (Wang et al., 2019). Hence, the combination of low temperature storage and controlled atmosphere (CA) technology has been used for many years to maintain physical and functional quality (Terry et al., 2009). For blueberries, a high concentration of carbon dioxide (CO2) has a positive impact on decay suppression (Retamales and Hancock, 2018). Recommendations range between 10–12 kPa CO2; higher levels elicit a negative effect on firmness, flavor, and titratable acidity (TA) content (Kader, 2003; Harb and Streif, 2004). Oxygen (O2) concentration has less impact on blueberry quality, although lowering it to 2–5 kPa is advised (Kader, 2003). O2 concentrations below 2 kPa lead to hypoxia and fermentation (Retamales and Hancock, 2018). However, applying standard CA can lead to abiotic stress derived from a sudden change in the surrounding atmosphere, negatively affecting quality (Falagán and Terry, 2018). The introduction of real-time respirometry has allowed the effects of CA to be monitored, reactivating research in this field. Previous studies have shown how targeted CA applications had a similar effect to continuous CA in extending shelf-life of onion, strawberry and avocado (Chope et al., 2007; Alamar et al., 2017). Based on these results, we hypothesized in this work that the graduated application of CA (GCA) could avoid this metabolic shock as it allows fresh produce to more slowly adapt to an optimal gaseous environment. This approach is based on the way modified atmosphere packaging (MAP) works, gradually reaching the respiratory equilibrium, instead of exposing the fresh produce to a sudden change in the atmosphere. Work on adaptive control of the gas diffusion in MAP has been successfully implemented before, e.g., preserving quality in blueberries and spinach (Lee et al., 2016). In this study, the MAP approach is translated to CA systems. The aim of this work was to study the benefits of GCA on the physiological and functional quality of “Duke” blueberries.
介绍 蓝莓（Vaccinium spp.）因其感官特性和促进健康的化合物含量而成为一种受欢迎的软水果（Manganaris等人，2014）。然而，蓝莓极易腐烂。它们在0℃下的贮藏寿命在14到20天之间变化，这取决于战前因素（即品种、成熟期、收获方法）和贮藏条件（Matiacevich等人，2013年）。减缓呼吸是水果代谢的主要过程（Gomes等人，2010），是延缓衰老的关键。呼吸主要受温度和呼吸气体环境的影响（Wang等人，2019）。因此，低温储存和控制气氛（CA）技术的结合多年来一直用于保持物理和功能质量（Terry等人，2009）。对于蓝莓，高浓度的二氧化碳（CO2）对抑制腐烂有积极影响（Retamales和Hancock，2018）。建议范围为10-12千帕二氧化碳；较高水平会对硬度、风味和可滴定酸度（TA）含量产生负面影响（Kader，2003；Harb和Streif，2004）。氧气（O2）浓度对蓝莓品质的影响较小，尽管建议将其降低至2–5千帕（Kader，2003）。氧气浓度低于2千帕会导致缺氧和发酵（Retamates和Hancock，2018）。然而，应用标准CA可能会导致非生物胁迫，这种非生物胁迫源于周围大气的突然变化，对质量产生负面影响（Falagan和Terry，2018）。实时呼吸测定法的引入使CA的作用得到了监测，重新激活了这一领域的研究。先前的研究表明，定向钙应用在延长洋葱、草莓和鳄梨的保质期方面与连续钙的效果相似（Chope等人，2007年；Alamar等人，2017年）。基于这些结果，我们在这项工作中假设，分级应用CA（GCA）可以避免这种代谢性休克，因为它允许新鲜产品更缓慢地适应的气体环境。这种方法基于改良的大气包装（MAP）的工作方式，逐渐达到呼吸平衡，而不是将新鲜农产品暴露在大气中的突然变化中。MAP中气体扩散的自适应控制工作之前已经成功实施，例如保存蓝莓和菠菜的质量（Lee等人，2016）。在本研究中，将MAP方法转化为CA系统。研究GCA对杜克蓝莓生理和功能品质的影响。 Materials and Methods Plant Material Blueberries (Vaccinium corymbosum L.) “Duke” were hand harvested at Cobrey Farms (Herefordshire, United Kingdom) on the 12 of July 2017 (season 1) and on the 27 of June 2018 (season 2) at their optimal maturity stage according to commercial standards defined by the company, considering color and maturity index. They were immediately transported in 600 g punnets to the Plant Science Laboratory at Cranfield University by refrigerated truck (2.5 h). Fruit were then directly transferred to the treatment boxes upon arrival at the laboratory and allowed to cool down for 24 h at 0°C prior treatment application.
材料和方法 植物材料 蓝莓（Vaccinium corymbosum L.）“杜克”于2017年7月12日（第1季）和2018年6月27日（第2季）在眼镜蛇养殖场（英国赫里福德郡）根据公司规定的商业标准，在其成熟期人工收获，同时考虑颜色和成熟指数。他们立即被冷藏卡车（2.5小时）用600克双关井网运送到克兰菲尔德大学的植物科学实验室。水果到达实验室后直接转移到处理箱中，并在处理前在0℃下冷却24小时。 Experimental Plan Forty-eight 4 L air-tight polypropylene boxes (L&L Nordic OÜ, Estonia) were used to store 1 kg of sound fruit each. They were kept in a cold room at 0°C and 90–95% relative humidity (RH). Four treatments were considered: (i) Control, flushed with regular atmosphere gas concentrations (20.9 kPa O2 and 0.03 kPa CO2); (ii) standard CA (5 kPa O2 and 10 kPa CO2); (iii) graduated CA 3 (GCA3) flushed to reach the desired CA partial pressures in 3 days; and (iv) GCA7 gradually flushed to reach the standard CA conditions in 7 days (Figure 1). Each condition was performed in triplicate. The combination of 5 kPa O2 and 10 kPa CO2 was selected as optimal according to previous work (Kader, 2003; Harb and Streif, 2004; Retamales and Hancock, 2018). For each CA condition, boxes were connected to an ICA6000 (International Controlled Atmosphere Ltd., Paddock Wood, Kent, United Kingdom) via PVC tubes; gases were bubbled through water to maintain a high RH%. For each treatment, an extra empty box was used as a baseline to avoid cross-contamination and allow respirometry calculations. The ICA6000 included an automated sample sequencing system to measure and control the gas concentration introduced in CA environments. The system was regularly checked for calibration with both fresh air and bottled calibration gas. Both temperature and RH were monitored in real-time with RD Sens RFS-TH (Prodisei, Valencia, Spain). Sampling was carried out on days 0, 7, 14, 21, and 28. Day 0 (one day after harvest) analysis were considered as baseline and samples were taken before placing the fruit in the treatment boxes.
实验计划 48个4L气密聚丙烯盒（L&L Nordic OÜ，爱沙尼亚）被用来储存1公斤健康水果。它们被保存在0°C和90-95%相对湿度（RH）的冷藏室中。考虑四种处理：（i）对照，用常规大气气体浓度（20.9 kPaO2和0.03 kPaCO2）冲洗；（ii）标准CA（5 kPaO2和10 kPaCO2）；（iii）刻度Ca3（GCA3）冲洗，在3天内达到所需的CA分压；（iv）GCA7在7天内逐渐冲洗达到标准CA条件（图1）。每项检查一式三份。根据先前的研究结果，选择5千帕氧气和10千帕二氧化碳的组合为（Kader，2003；Harb and Streif，2004；Retamales and Hancock，2018）。对于每个CA条件，盒子通过PVC管连接到一个ICA6000（国际控制大气有限公司，Paddock Wood，Kent，United Kingdom）；气体通过水鼓泡以保持较高的RH%。对于每种治疗方法，使用一个额外的空盒子作为基线，以避免交叉污染，并允许进行呼吸计量计算。ICA6000包括一个自动样品测序系统，用于测量和控制CA环境中引入的气体浓度。定期用新鲜空气和瓶装校准气体对系统进行校准检查。用RD-Sens-RFS-TH（西班牙巴伦西亚Prodisei）实时监测温度和相对湿度。在第0、7、14、21和28天进行取样。第0天（收获后一天）分析被视为基线，并在将水果放入处理箱之前取样。 内容很好
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