文獻翻譯 （ 20*屆本科） 學 院： 專 業： 班 級： 姓 名： 學 號： 指導教師： 20*年 5 月 Emerging technologies for keeping microbial and sensory quality of minimally fresh processed fruits and vegetables The emphasis in post-harvest fruit protection against quality attributes losses, physiological disorders, diseases and insects has shifted from using agro-chemicals to various alternative techniques, including biological control, cultural adaptations and physical methods such as controlled atmosphere (CA), MAP and irradiation. Given the restrictions of chemical use in plant foods and because many of them cause ecological problems or are potentially harmful to humans and may be withdrawn from use, the advantage of these alternative techniques is that no chemicals are involved (Arts, 1995； Graham and Stevenson, 1997； Reddy et al., 1998； Mathre et al., 1999； Sanz et al., 1999； Daugaard, 2000； Harker et al., 2000； Marquenie et al., 2003). Additionally, preservation techniques are becoming milder in response to demands of consumers for higher quality, more convenient foods that are less heavily processed and preserved and less reliant on chemical preservatives (Abee and Wounters, 1999). The unique way to assure microbial and sensory quality of minimally fresh processed plant products relies on refrigerated storage and distribution, although combination of refrigeration and subinhibitory preservation techniques could prolong their shelf-life. As mentioned above, many non-conventional methods are now being investigated； however, there are some limitations to their application since some methods are not applicable to fresh-cut fruits and vegetables because of damage to plant tissue but only to liquid foods such as fruit juices (Carlin and Nguyen-the, 1997). Therefore, in this section those techniques that can be used to preserve fresh processed plant foods will be revised. The most critical step in the production chain of minimal fresh processing of fruits and vegetables is washing-disinfection. For this reason, special attention to the alternative sanitizing agents as well as the new technologies for disinfection of these commodities will be given. To develop or improve washing and sanitizing treatments, special attention should be paid to the compatibility of treatments with commercial practices, cost, absence of induced adverse effects on product quality and the need for regulatory approval and consumer acceptance (Sapers, 2001). Some alternatives to sanitizing agents are: O3, ClO2, peracetic acid (about 90100 ppm), H2O2, organic acids (acetic, lactic, citric, malic, sorbic and propionic acids at 300500 mg/ml), electrolysed water, radio frequency, hot water treatments and UV-C radiation (Adams et al., 1989； Masson, 1990； Castaer et al., 1996； Toms-Barbern et al., 1997； Delaquis et al., 1999, 2000, 2004； Sapers, 2001； Suslow, 2002； Jacxsens, 2002； Aguayo, 2003； Allende, 2003). 1. Hydrogen peroxide Treatments of hydrogen peroxide (H2O2) seem to be a promising alternative to chlorine for disinfecting minimally fresh processed vegetables (Soliva-Fortuny and Martn-Belloso, 2003). H2O2 is generally recognized as safe (GRAS) for some food applications, but has not yet been approved as an antimicrobial wash. It does not produce residues since it is rapidly decomposed by the enzyme catalase to water and O2 (Sapers, 2001). Various experimental antimicrobial applications of H2O2 for foods have been described, including preservation of vegetable salads, berries and fresh-cut melons (Hagenmaier and Baker, 1997) since it reduces microbial populations and extends the shelf-life without causing loss of quality. Sapers and Simmons (1998) recommended its use for fresh-cut melon as it extended the shelf-life for 45 days in comparison to chlorine treatments. However, they demonstrated that H2O2 is injurious to some commodities, causing bleaching of anthocyanins in mechanically damaged berries. H2O2 vapour delayed or reduced the severity of bacterial soft rot in fresh processed cucumber, green bell pepper and zucchini, but no effect on spoilage of fresh-cut broccoli was found (Hagenmaier and Baker, 1997). Additionally, an extended shelf-life was found in fresh processed cucumbers, green bell peppers and zucchini after washing in a 510 per cent solution of H2O2 for 2 min (Sapers and Simmons, 1998). It means that the applicability of H2O2 to a broad range of minimally fresh processed vegetables should be determined, especially with commodities that are subject to rapid spoilage. 2. Acidic electrolysed water This is a new disinfectant technique for fresh produce that has been shown to be efficient due to its antimicrobial and antiviral activities for fruit and vegetables (Izumi, 1999； Koseki and Itoh, 2000). Electrolysis of water containing a small amount of sodium chloride generates a highly acidic hypochlorous acid solution containing 10100 ppm of available chlorine. Koseki et al. (2001) found that acidic electrolysed water (pH 2.6, oxidation reduction potential, 1140mV； 30 ppm of available chlorine) reduced viable aerobes in shredded lettuce by 2 log cfu/g within 10 min, showing a higher disinfectant effect than ozonated water. They reported that the use of this new technique could be applicable for food factory hygiene, meaning that the use of acidic electrolysed water at home or restaurant kitchen just before eating fresh fruits and vegetables could prevent poisoning. According to this, Park et al. (2002) reported population reductions on lettuce leaves exceeding 2.49 log units for E. coli O157:H7 and L. monocytogenes and Horton et al. (1998) reported population reductions of E. coli O157:H7 on apples of 3.74.6 log units cfu/g. However, Izumi (1999) only found 1 log unit cfu/g reduction in the microbial population of fresh-cut vegetables. 3. Chlorine dioxide Chlorine dioxide (ClO2) is a strong oxidizing agent (about 2.5 times the oxidative capacity of chlorine) having a broad biocide efficacy (Singh et al., 2002), including a good biofilm penetration. To date, the FDA (USFDA, 1998) has allowed the use of aqueous ClO2 in washing of uncut and unpeeled fruit and vegetables. However, ClO2 is unstable and it must be generated on-site and can be explosive when concentrated (Jacxsens, 2002). Zhang and Farber (1996) found that the initial microbial load decreased by 1 log cycle of cfu/g for shredded lettuce inoculated with L. monocytogenes at levels of 5 mg/l ClO2 in aqueous solution. However, Reina et al. (1995) found that bacterial populations present on fresh processed cucumbers were not greatly influenced by ClO2 treatment, even at concentration of 5.1 mg/l. More recently, Singh et al. (2002) found that increasing the concentration of ClO2 in deionized water (5 mg/l for 1 and 5 min) resulted in a decrease in E. coli O157:H7 population on lettuce and baby carrots in comparison to washing with deionized water (control) for the same period. Increasing the washing period from 1 to 15 min with aqueous ClO2 (5 mg/l) showed no significant reduction in the population of E. coli O157:H7 on shredded lettuce. However, after washing baby carrots a reduction in E. coli O157:H7 was found. 4. Organic acids Several organic acids have been tested as alternative disinfectants to sanitize fresh-cut vegetable surfaces (Hilgren and Salverda, 2000). They may retard and/or prevent the growth of some microorganisms (Beuchat, 1998). Their antimicrobial activity is not generally due to killing of the cells but they affect the cells ability to maintain pH homeostasis, disrupting substrate transport and inhibiting metabolic pathways (Seymour, 1999). Peracetic acid has been recommended for treatment of process water (Hilgren and Salverda, 2000)； however, population reductions for aerobic bacteria, coliforms, yeast and moulds on fresh-cut celery, cabbage and potatoes, treated with 80 ppm peracetic acid, were less than 1.5 log units cfu/g (Forney et al., 1991). Wright et al. (2000) obtained a 2 log units cfu/g reduction in apple slices inoculated with E. coli O157:H7 using 80 ppm peracetic acid, with an interval of 30 min between inoculation and treatment. On the other hand, Wisniewsky et al. (2000) found a reduction of less than 1 log unit cfu/g at the same concentration but in an interval of 24 h. Citric acid has been proposed as a very good coadjutant to the washing of fresh-cut fruit and vegetables due to its antibrowning power. It is a phenolase Cu-chelating agent and the inhibition of PPO was attributed to its chelating action (Jiang et al., 1999). Santerre et al. (1988) reported that application of citric acid can prevent browning of sliced apple thus extending shelf-life and it was shown that the combination of citric acid and ascorbic acid exhibited even more beneficial effects (Pizzocaro et al., 1993). Additionally, Jiang et al. (2004) found that the application of citric acid was effective in extending shelf-life and maintaining the quality of fresh-cut Chinese water chestnut slices during storage. 5. Ozone Ozone (O3) is a strong oxidant and potent disinfecting agent and, when it is applied to food, it leaves no residues since it decomposes quickly. The biocide effect of O3 is caused by a combination of its high oxidation potential, reacting with organic material up to 3000 times faster than chlorine (EPRI, 1997). Even though it is new for the USA, it has been utilized in European countries for a long time (Guzel-Seydima et al., 2004). For instance, it has been commonly used as a sanitizer in water treatment plants since the early 1900s (Gomella, 1972) and also for disinfection of swimming pools, sewage plants, disinfection of bottled water and prevention of fouling of cooling towers in Europe (Gomella, 1972； Rice et al., 1981； Legeron, 1982； Schneider, 1982； Echols and Mayne, 1990； Costerton, 1994； Videla et al., 1995； Strittmatter et al., 1996). In 1997, an expert panel decreed that O3 was a GRAS substance for use as a disinfectant or sanitizer for foods when used in accordance with good manufacturing practices in the USA (Suslow, 2003) and it has now been approved for use as a disinfectant or sanitizer in foods and food processing in the USA (USDA, 1997, 1998). The bactericidal action of O3 has been studied and documented on a wide variety of organisms, including those that are resistant to chlorine, extending the shelf-life of a number of fruit and vegetables (Fetner and Ingols, 1956； Norton et al., 1968； Rice et al., 1982； Foegeding, 1985； Ishizaki et al., 1986； Foegeding and Busta, 1991； Restaino et al., 1995； Beuchat, 1998； Richardson et al., 1998； Aguayo, 2003). In fact, it has been proven that O3 is suitable for washing and sanitizing solid food with intact and smooth surfaces (e.g. fruit and vegetables) and ozone-sanitized fresh produce has recently been introduced in the USA market. The use of O3 to sanitize equipment, packaging materials and the processing environment is currently being investigated (Kim et al., 2003). The modus operandi of O3 implicates the destruction of microorganisms by the progressive oxidation of vital cellular components. The bacterial cell surface has been suggested as the primary target of ozonation (Guzel-Seydima et al., 2004). Khadre and Yousef (2001) compared the effects of O3 and H2O2 against foodborne Bacillus spp. spores and found that O3 was more effective than H2O2. In shredded lettuce treated with O3, Kim et al. (1999) reported that bubbling O3 gas (49 mg/l, 0.5 l/min) in a lettuce-water mixture decreased the natural microbial load by 1.51.9 log unit cfu/g in 5 min. As a consequence, a number of patents have been issued for using O3 to treat fruit and vegetables. However, the results obtained by Singh et al. (2002) have shown that treatment with ozonated water (5.2 mg/l) did not result in any significant reduction in E. coli O157:H7 populations during 115 min of washing in shredded lettuce, although they found a reduction in microbial counts on baby carrots after 10 min exposure to 5.2 mg/l ozonated water. The reduced efficacy of ozonated water during lettuce washing might be due to more O3 demand of organic material in the medium as it was also found in melon fresh-cut pieces (Aguayo, 2003). It was shown that the use of O3 in the storage of vegetable products could have detrimental effects, as happened in some berries with very thin skin which can be easily penetrated by O3, oxidizing the fruit (Norton et al., 1968； Rice et al., 1982). The antimicrobial efficacy can be enhanced considerably when ozonation is combined with other chemical (e.g. H2O2) or physical (e.g. UV-C radiation) treatments. Mechanical action is also needed as a means to dislodge microorganisms from the surface of the food and expose them to the action of the sanitizer (Kim et al., 2003). 6. Hot water treatments Heat preservation is one of the oldest forms of preservation known to man and has the potential to provide barriers to reduce microorganisms and inhibit enzyme activity, but this treatment is incompatible with fresh processed plant food since heat is associated with destruction of flavour, texture, colour and nutritional quality (Orsat et al., 2001). However, hot water treatments used to reduce or eliminate pathogens offer an alternative means to control the quality deterioration of fresh fruit and vegetables, as well as a means of enzyme inactivation (Bolin and Huxsoll, 1991). These mild heat treatments consist of subjecting the products to temperatures of 5090C for periods of time not exceeding 15 min. Loaiza-Velarde et al. (1997) reported that dipping lettuce in water at 4555C would extend the shelf-life and visual quality of minimally fresh processed lettuce by inhibiting the activity of PAL, which is the enzyme that initiates biosynthesis of phenolic compounds that leads to visible discoloration along the cut edge of the lettuce leaf (Lpez-Glvez et al., 1996). Additionally, Li et al. (2001) suggest that heat (50C) treatment combined with 20 mg/l free chlorine for 90 s may have delayed browning and reduced initial populations of some groups of microorganisms naturally occurring on iceberg lettuce, but enhanced microbial growth during subsequent storage due to tissue damage. Delaquis et al. (1999, 2000) found a reduction of 2 log cfu/g in initial microbial load in lettuce washed with chlorinated water (100_l/l) at 47C for 3 min, compared to washing at 4C. However, in 2004, Delaquis et al. found that comparison between lettuce washed at 4C and 50C revealed that disinfection of the lettuce was improved by heat, although the difference in total microbial populations was only 1 log cfu/g. The application of mild heat treatments is commonly by using hot air, hot water or steam. Among them, hot water is the easiest conditioning treatment since it offers a great flexibility and easiest control (Barkai-Golan and Philips, 1991). However, Orsat et al. (2001) have demonstrated that it is possible to treat carrot sticks thermally with radio-frequency energy in less than 2 min at an internal temperature of 60C, to reduce the microbial load before packaging while minimizing the detrimental effects on the sensory quality of the fresh-like product. The main difference in using this treatment is that in radio-frequency heating, the energy is absorbed directly within the material, the heating is rapid and uniform throughout the material and the technology is relatively simple to adapt to an existing processing line. 保持 微創 新鮮 已 加工果蔬的微生物和感官質量的新興技術 （英文文獻中文譯稿） 收獲后水果對質量損失、生理病變、蟲害等的保護的重點已經從使用農藥轉變為各種替代技術，包括生物控制、文化適應和物理方法如控制氣氛、 MAP 和輻射。因為化學品會引起生態問題并對人體產生潛在危害，所以在農產品中使用有限制或禁止使用， 這些替代技術的優點是不涉及化學品 。此外，保護技術正響應消費者對高質量、 不那么嚴重處理和維護 并 減少對化學防腐劑依賴方便食品 的需求。 雖然亞抑菌保鮮和冷藏 技術的組合可以延長 農產品的 保質期 ，但保證微生物和微創新鮮已加工農產品的感官質量的獨特途徑還是依靠冷藏庫和配送。 如上所述，許多非傳統的方法正在研究，然而由于會 損害植物組織 ，所以 有些方法并不適用于鮮切水果和蔬菜 還有液態食品比如果實，因此應用有一些局限性。所以，這部分用來保存新鮮以加工的農產品的技術將被修改。 果蔬 的最小新鮮 加工 在 生產鏈 中 最關鍵的步驟是清洗消毒。 基于這個原因，要特別注意選擇對這些產品消毒藥物和新興技術。為了 發展改善清洗和消毒處理 ，需要特別注意在產品質量和 監管機構的批準和消費者接受 上的商業慣例、成 本、缺乏引起的不良影響的兼容處理。 一些消毒藥物的選擇是：臭氧，二氧化氯，過氧乙酸（約 90-100 ppm 的），過氧化氫，有機酸（醋酸，乳酸，檸檬酸，蘋果酸，在 300-500毫克 /毫升山梨酸和丙酸），電解水，無線電頻率，熱水治療和 UV - C 輻射 等。 1. 過氧化氫 過氧化氫（ H2O2）的使用似乎是 替代氯消毒微創新鮮 已加工 蔬菜 的比較好的方法。過氧化氫是一些食品應用中普遍認為安全的，但尚未被批準為抗菌洗劑。它不會產生殘留， 因為它 會 迅速分解酶的過氧化氫酶的水和氧氣 。對食品使用的各種實驗的抗菌所用的過氧化氫， 包括 蔬菜沙拉，新鮮漿果和切瓜保存 ，因為它減少了微生物群并延長貨架期而不造成質量損失。 Sapers 和 Simmons（ 1998）認為在鮮切瓜上使用過氧化氫比用氯來消毒要延長 4 至 5 天的貨架期。但是，他們也表明過氧化氫對某些產品有損害，會造成漿果的機械損害而漂白了花青素。過氧化氫的蒸汽延緩或減少了在新鮮已工的黃瓜、青椒和西葫蘆中細菌性軟腐病的嚴重性，但發現對鮮切青花菜沒有損壞效果。此外，度為 5%至 10%的過氧化氫沖洗2 分鐘之后，發現可以延長黃瓜、青椒和西葫蘆的貨架期。這就意味著，在微創新鮮已加工蔬菜的范圍中已確定過氧化 氫是適用的，特別是容易迅速腐爛的商品。 2. 酸性電解水 由于 對 果蔬活動 能 抗菌和抗病毒 ，這是一個 新的已被證明 對 新鮮農產品是有效的消毒技術 。含有少量氯化鈉的電解水生成含有 10-100 ppm 的有效氯的高酸度的次氯酸。 Koseki 等 發現酸性電解水（ pH值 2.6，氧化還原電位， 1140mV，有效氯 30 ppm） 在 10 分鐘內生菜絲的可行需氧菌 2 log cfu/g，表明了比臭氧水殺菌有更好的效果。 他們報告說，這一新技術的使用可 適用 于食品廠 的 衛生，這意味著在家里或餐廳 廚房 吃新鮮果蔬 前使用 酸性電解水可預防中毒。 根據這個， Park 等指出生菜葉子上減少了超過 2.49 log 單位的大腸桿菌和李斯特菌，而 Horton 等指出在蘋果上大腸桿菌減少了 3.7 4.6 log單位。然而， Izumi 發現在鮮切蔬菜上只減少了 1 log 單位 cfu/g 微生物種群。 3. 二氧化氯 二氧化氯（ ClO2）是一種強氧化劑（約 2.5 倍的氯氧化能力） ， 具有廣泛的生物殺蟲劑藥效 并 包括一個良好的生物膜的滲透。 至今 ， 食品藥品管理局 已經允許二氧化氯水溶液在未經切割和削皮的果蔬 的清洗 中 使用。 Zhang 和 Farber 發現，生菜絲的 最初的微生物 在接種了在 5 mg/l 的二氧化氯水溶液中的李斯特菌 后每 cfu/g 下降 1 log 周期。然而，二氧化氯是不穩定的，它必須現場及時生成，而且當集中起來后會爆炸。 然而， Reina 等 發現，細菌群體 在 新鮮 的已 處理黃瓜 上 二氧化氯處理 的 影響 并不大 ， 即使是 在 5.1 mg/l 的 濃度 中。最近， Singh 等人發現相比小胡蘿卜在同一時期用去離子水（對照）清洗，增加去離子水（ 5 mg/l， 1 和 5 分鐘）中二氧化氯的濃度會使生菜中的大腸桿菌減少。 將用二氧化氯（ 5 mg/l）的洗滌時間從 1 分鐘增加至 5 分鐘沒有發現生菜絲上大腸桿菌數量的減少，但在小 胡蘿卜上發現減少了。 4. 有機酸 有幾種作為可選擇的消毒鮮切蔬菜表面的消毒劑的有機酸已做過測試，它們 可能會延緩 并 /或預防某些微生物的生長 。它們的抗菌活性不僅能殺死一般的細胞，并且能夠影響細胞的活性來維持 pH 平衡，擾亂傳遞并抑制底物的代謝途徑。 過氧乙酸已被推薦用于水處理過程，然而對于用 80 ppm 的過氧乙酸減少 鮮切芹菜 、 白菜和土豆 上 好氧細菌 、 大腸菌群 、 酵母 菌 ，均小于 1.5 log 每單元 cfu/g。 Wright等人得出，在蘋果切片用