Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/52006
標題: Investigation of the Microbial Quality and Residues of Chemical Reagents in Fresh-Cut Vegetables in Taiwan, and the Application of Gamma Irradiation on the Extension of Their Shelf-life
調查台灣市售生鮮截切蔬菜的微生物含量及化學藥劑殘留量,並應用伽馬照射延長其保存期限
作者: 蔡汶哲
Tsai, Wen-Che
關鍵字: fresh-cut vegetables
生鮮截切蔬菜
microbial quality
chemical residues
irradiation
sensory evaluation
微生物
化學藥劑殘留
輻射照射
品評
出版社: 食品暨應用生物科技學系所
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摘要: 生鮮截切蔬果在加工過程中易產生褐變或是被微生物汙染,因此廠商會添加抗氧化劑或是抗菌劑以防止產品品質降低。為了解此類販售產品是否有化學藥劑殘留或受微生物汙染,本研究的第一階段是針對市售截切蔬菜進行上述的檢測。而在第二階段,挑選常用及易受微生物汙染的蔬菜,進行輻射照抑制微生物生長並延長截切蔬菜的保存期限,並分析照射對其物理性質及感官品評的影響。 第一階段,8種即食截切蔬菜包含葉菜類、根莖類共42件,5種即煮截切蔬菜樣品共15件,2種芽菜類樣品共24件,進行微生物和化學藥劑殘留檢測。微生物檢測結果中,總生菌數菌數大於105 CFU/g、大腸桿菌群菌數大於103 MPN/g、和大腸桿菌菌數大於10 MPN/g為不合格,而金黃色葡萄球菌和沙門氏菌不可檢出。即食截切蔬菜產品的總生菌數共13件不合格、大腸桿菌群共12件不合格,大腸桿菌、金黃色葡萄球菌和沙門氏菌則未被檢出。其次,在即煮截切蔬菜15件產品中,有10件樣品的生菌數大於105 CFU/g,9件樣品的大腸桿菌超過103 MPN/g,因其食用前需煮過故可去除一般微生物故合格;而大腸桿菌、金黃色葡萄球菌和沙門氏菌皆未檢出。芽菜類24件所含之總生菌數與大腸桿菌群皆已超過衛生署所定的規範,且有2件樣品的大腸桿菌數也超過規範,而金黃色葡萄球菌和沙門氏菌則未被檢出。另外,所有芽菜類、即食截切蔬菜和即煮截切蔬菜的樣品在化學藥劑殘留測定中,均未檢出餘氯和二氧化硫的殘留,而抗壞血酸和檸檬酸都符合規定沒有超標。本實驗第二階段利用輻射線照射6種常見截切蔬菜(萵苣、高麗菜、苜蓿芽、豌豆苗、紅蘿蔔與馬鈴薯)。結果顯示截切蔬菜經照射後能有效降低微生物含量,樣品在低溫下存放9天後,高劑量(3 kGy)照射組與未照射組相比,葉菜類的總生菌數可降低約6 log CFU/g、芽菜類下降約4 log CFU/g,而根莖類降低約4-6 log CFU/g。另外,由酵母菌和黴菌數的檢測結果發現葉菜類和芽菜類可降低約6 log CFU/g,而根莖類下降約4-6 log CFU/g。此外,照射對蔬菜組織破壞程度以電解液釋出量(Electrolyte leakage)的多寡來判斷,在高劑量(3 kGy)照射下的EL值和其他劑量相比,明顯高於其他劑量,且隨著存放時間增加EL值亦會增加,故蔬菜組織的破壞程度會同時受到照射劑量和存放天數影響;照射後的樣品在低溫存放9天後,照射組的樣品和未照射組相比沒有顯著差異,照射對樣品色澤影響小。輻射照射過的樣品,以紅蘿蔔和高麗菜進行官能品評,以了解照射樣品對顧客喜好性的影響,其餘樣品因存放後會有水分滲出或外觀不佳不適食用。品評結果顯示,高麗菜在0.5 kGy劑量照射後,外觀分數略微下降(0.56%)而風味(7.22%)、質地(5.00%)和整體接受度(5.56%)皆上升。然而,在高劑量(2 kGy)照射的高麗菜,四種項目的分數皆下降,品評者對於樣品的接受度低。而紅蘿蔔在0.5 kGy劑量照射後,外觀(3.33%)、風味(2.22%)、質地(5.00%)和整體接受度(0.56%)皆下降,而在1 kGy劑量照射的紅蘿蔔,四種項目的分數皆上升,比0.5 kGy照射的紅蘿蔔好。高劑量(2 kGy)照射的紅蘿蔔,品評者對於樣品的總體接收度較照射1 kGy的樣品低。因此,高麗菜在0.5 kGy的劑量可以增加其感官品評,而紅蘿蔔則是在1 kGy的劑量可以增進其感官品評。
Fresh-cut fruits and vegetables are easy to have browning reactions and microbial contamination during the processing. Therefore, manufactories may add antioxidants or antibacterial agents to avoid the quality reduction of these products. Thus, the first part of this study was to investigate the microbial quality and the amounts of chemical residuals in fresh-cut vegetables. In the second part of this study, vegetables which are easily contaminated by microorganisms were irradiated to inhibit the growth of microorganisms and to increase its shelf life. Moreover, the effects of irradiation on the physical and sensory quality of vegetables were also investigated. In the first part, a total of 42 ready-to-eat (RTE) vegetables (classified into leafy vegetable and rhizomes), 15 ready-to-cook (RTC) vegetables, and 24 sprout products were investigated. The total plate counts above 105 CFU/g, coliform counts above 103 MPN/g, and Escherichia coli counts above 10 MPN/g were unacceptable. In addition, Staphylococcus aureus and Salmonella spp. can't be detected. Among 42 RTE samples, 13 and 12 samples were unacceptable due to the too high amounts of total plate count and coliform count, individually; while, E. coli, S. aureus, and Salmonella spp. were not detectable in all RTE samples. For 15 RTC samples, 10 samples had total plate count higher than 105 CFU/g, and 9 samples had coliform count higher than 103 MPN/g. Since RTC products will be cooked before eating, it is sure that microorganisms normally can be eliminated before ingestion with proper cooking process. There was no contamination of S. aureus and Salmonella spp. in all RTC samples. All 24 sprout products were unacceptable in total plate count and coliform count. Moreover, two samples were contaminated by E. coli, but S. aureus and Salmonella spp. were not detectable in all sprout samples. Additionally, in all RTE, RTC, and sprout samples, no residual chloride and sulfur dioxide was detected, and the content of ascorbic acid and citric acid were all under the legal limits. In the second stage of this study, food irradiation was applied to six common vegetables (lettuce, cabbage, alfalfa sprouts, pea shoot, carrot, and potato). The results showed that gamma irradiation could effectively reduce the growth of microorganism. After the storage for 9 days, the log reduction for total plate counts could reach to 6 log CFU/g, 4 log CFU/g, and 4-6 log CFU/g for 3-kGy irradiated leafy vegetables, rhizome, and sprouts, respectively. Moreover, the log reduction of yeast and mold on leafy vegetables, rhizome, and sprouts were about 6 log CFU/g, 6 log CFU/g, and 4-6 log CFU/g, respectively. The damage level of food irradiation on tissues of vegetables was expressed by the electrolyte leakage value (EL). The EL values at 3 kGy dose were higher than other dosages for all test samples, and the EL also increased with the increase of storage time. Therefore, the tissues of vegetables were affected by both irradiation dose and storage time. After samples were stored for 9 days, the color of irradiated samples had no significant difference compared with non-irradiated samples. The irradiated cabbage and carrot were used to perform the sensory evaluation, for understanding the effects of irradiation on customer's preference. Due to other vegetables released water or had bad appearance after storage, they were not suitable for sensory evaluation. The appearance score of cabbage treated with 0.5 kGy dose slightly decreased (0.56%); however, odor score (7.22%), texture score (5.00%), and overall acceptability score (5.56%) were increase, as compared to un-irradiated cabbages. At high irradiation dose of 2 kGy, the score of four sensory items decreased, since most people didn't accept this level of irradiated cabbage. Moreover, the score of carrot treated with 0.5 kGy dose were decreased in appearance (3.33%), odor (2.22%), texture (5.00%), and overall acceptability (0.56%). At irradiation dose of 1 kGy, the score of four sensory items increased compared with carrot treated with 0.5 kGy dose. Carrot irradiated with 2 kGy dose had lower score in overall acceptability than that treated with 1 kGy. Therefore, irradiation dose at 0.5 kGy could improve the sensory and hygiene quality of cabbage, and irradiation dose at 1 kGy had better sensory effect on carrot.
URI: http://hdl.handle.net/11455/52006
其他識別: U0005-2308201103151900
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-2308201103151900
Appears in Collections:食品暨應用生物科技學系

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