鲜切水果的氧化

1、Quality of fresh-cut fruits and vegetablesas affected by exposure to abiotic stressPostharvest Biology and Technology 48 (2008) 155162Agriculture and Agri-Food Canada Atlantic Food and Horticulture Research Centre，Pacific Agri-Food Research Centre非生物因素 Abiotic stress is defined as the negative impac

2、t of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology of the organism in a significant way. biotic stress 非生物因素对鲜切果

3、蔬的质量和营养状况有重要影响，而对于鲜切果蔬的加工、包装和储藏中的非生物因素的定义和记录的相关研究较少。很多指标可用来描述非生物因素的影响，如褐变（鲜切果蔬的切口面）、呼吸加快、乙烯产生、Vc含量降低、组织变软等从文献评论可看出，目前对于非生物因素的了解水平和机制是相对浅薄的。为能发展有效的策略调整非生物因素对鲜切果蔬的质量和营养影响，对此作进一步研究。大部分的已发表的植物研究是关于非生物因素在生理、生化或（和）基因表达方面对生长植物的影响。也有相当一部分科学文献是关于生产、加工和采后对整果的影响。很少一些是采前生产、加工技术、贮藏环境和包装处理过程中非生物因素对鲜切果蔬的影响方面的。对鲜切非

4、生物影响的描述主要集中于现象而不是应力诱发的机制，这篇综述也就主要参考各文献中的现象。这些鲜切果蔬产品的症状包括褐变（尤其是鲜切面由组织损伤引起的）、一系列氧化过程(Bhagwat et al.,2004) 、呼吸和乙烯产生增加(Aguayo etal., 2004a) 、loss of flavour and texture (Lamikanra and Richard,2002), weight loss/dehydration (Piagentini et al., 2002), 营养素含量水平降低如Vc(Gil et al., 2006)、developmentof off-odour

5、s (Beaulieu, 2006a)、membrane breakdown(Hodges et al., 2000), 和组织软化 (Aguayo et al.,2004a). Fresh-cut fruits and vegetablesdemonstrate increased respiration rates and wound-inducedethylene production, and increase the surface area per unit volume,thus exacerbating water loss (Toivonen and DeEll, 2002)

6、.低温贮藏过程中Temperature-induced injury、加工和包装过程中的物理磨损并因此导致的abusive atmospheres or desiccation（干燥），这些都是非生物因素影响鲜切果蔬生理和代谢特性并导致不友好的风味、组织、营养质量影响产生的例子(Toivonen, 2003a) 。鲜切果蔬的质量同时受内在和外在因素的影响；内在因素也就是代谢特性影响fresh-cut processing and storage，外在因素代表环境状况且会抑制或加速内在因素的作用。内在因素包括形态学、生理学、生化学上的防御机制，基因型，应力诱发衰老机制和processing ma

7、turity；外在因素有贮藏温度、湿度、cutting-knife sharpness和化学试剂。The primary sources of abiotic stress, how fresh-cut produce responds to stresses, and how stress translates to quality decline of fresh-cut fruits and vegetables will be addressed in this review.2. Preharvest stress effects and genetic factorsThe pos

8、tharvest quality of fruits and vegetables can be influenced by a large variety of preharvest and genetic factors, but it is generally accepted that produce which is stressed in the preharvest stage will invariably have reduced postharvest quality (Weston and Barth, 1997; Galvis-Sanchez et al., 2004;

9、 Calderon- Lopez et al., 2005).examplereported by Hong et al. (2000)slices made from tomatoesthat were harvested from plants grown using hairyvetch（毛苕子） mulch were firmer, had lesswater-soaked areas (indicativeof chilling-related injury), and exhibited less increases in electricalconductivity (indic

10、ator of stress-induced membrane damage)than slices from plants grown using black polyethylene（黑色聚乙烯 ） mulch.还有很多采前因素影响fresh-cut quality的例子，这只是其一In another study, low light intensity resulted in shortened shelf-life of greenhouse grown long English cucumbers (Cucumis sativus L.) primary due to the fa

11、ct that low light led to reduction in total chlorophyll content of the cucumber skin (Lin and Jolliffe, 1996)Cultivar/genetic effects on the sensory and nutritional quality of fresh-cut fruits and vegetables have received considerableattention.It has been well documented that different cultivars(品种)

12、can vary widely in response to biotic and/or abiotic stresses and in bioactive components(e.g. Hodges et al., 1995, 1996, 1997;Hodges and Lester, 2006; Weston and Barth, 1997; Lee and Kader, 2000).Maturity of the harvested product can also influence itsresponse to fresh-cut stress, thus emphasizing

13、the fact that stress tolerance changes with maturity. The fresh-cut industry often prefers to process firmer and less mature fruit to improve shelf-life duration. For example, Gorny et al. (1998) found that although overripe peach and nectarine slices had a higher organoleptic sensory rating than ma

14、ture green fruit, slices from the overripe fruit demonstrated significantly shorter shelf-life compared to less mature fruit based on visual quality.成熟度3. Postharvest physical damageWounding，some form of processing (e.g. slicing, chopping, trimming整修, peeling,coring, and/or shredding切丝).Cutting shap

15、e has also been identified as having an effect on quality of fresh-cut commodities, often in association with precut product turgidity. Cut cylinders of melon stored for up to 10 days were firmer than slices or trapezoidal（不规则） sections, but exhibited a higher degree of translucency（半透明） than the ot

16、her two cuts; trapezoidal cutting was determined to be the optimal protocol （最佳方法)(Aguayo et al., 2004a). 还有The sharpness of the cutting bladeThe actual cutting process results in major tissue disruption as previously sequestered enzymes and substrates mix,hydrolytic enzymes are released and signali

17、ng-induced woundingresponses may be initiated, as shown by Myung et al. (2006)for strawberries (Fragaria ananassa L.).实际的切割过程导致之前隐蔽的酶和物质的混合、水解酶的释放和损伤反应的启动对应的组织劣化。responses to woundingvolatile compounds may be released upon woundingEnzymatic activation of both WIPK wound-induced protein kinase and SI

18、PK mitogen-activated protein kinasean increase in both respiration rate and ethylene productione.g.4. Storage conditionsThe two storage parameters that will primarily be considered in this section are storage temperatures and atmospheric compositions; given the amount of recent work pertaining（关于） t

19、o chemical and alternative preservation techniques of fresh-cut commodities, these topics warrant a review of their own. It is not always easy to separate interactions between chilling stress and physical damage or other storage protocol during fresh-cut storage, and characterizing the individual ef

20、fects of less-than-optimum cold temperatures and storage atmospheres on un-cut commodities can often assist in elucidation（说明） of how each of these storage conditions may impact quality of resultant fresh-cut products .Exposure to cold temperatures following harvest in order to minimize and/or inhib

21、it the effects of wounding stress is recognized as one of the principal factors controlling quality of fresh-cut leafy vegetables (Artes and Allende, 2005).For example, overall quality declined, microbial load(微生物负荷) increased, and sensorial quality declined for fresh-cut tomato stored at 0 C over 1

22、4 days but these changes occurred less rapidly than in product that was held at 5 C (Aguayo et al., 2004b).A larger percentage of fresh-cut products are stored andA larger percentage of fresh-cut products are stored andmarketed in modified atmosphere packaging (MAP) in marketed in modified atmospher

23、e packaging (MAP) in conjunction with chilled storage and other preservation conjunction with chilled storage and other preservation protocols.MAP essentially maintains the quality of fresh-protocols.MAP essentially maintains the quality of fresh-cut products by matching the oxygen transmission rate

24、 (OTR) cut products by matching the oxygen transmission rate (OTR) of the packaging film to the respiration rate of the of the packaging film to the respiration rate of the packaged product; Opackaged product; O2 2 and COand CO2 2 levels within the package can levels within the package can also chan

25、ge as a function of area of the film as well as also change as a function of area of the film as well as ambient temperature (Jacxsenset al., 2000; Al-Ati and ambient temperature (Jacxsenset al., 2000; Al-Ati and Hotchkiss, 2003).Hotchkiss, 2003).Advantages of MAP applications using un-cut horticult

26、ural commodities often translate into similar quality benefits with their fresh-cut derivatives. As examples, MAP treatments of tomato slices led to better appearance and overall quality than ambient air-packaged controls (Aguayo et al., 2004b). Moreover, MAP-treated fresh-cut kohlrabi (B. oleracea

27、var. gongylodes) had reduced microbial population growth and better colour retention than air-stored material Escalona et al., 2003). However, using MAP protocols for fresh-cut fruits and vegetables has often led to the generation of anaerobic conditions and/or high CO2 levels which ultimately have a detrimental effect on product quality through production of ethanol, acetaldehyde, off-flavours and odours (e.g. Beaulieu, 2006b and Saltveit, 2003 ). 5. ConclusionsThe key to developing improved shelf-life, quality and nutritional status in f