外文翻譯--采后熱處理對(duì)番茄品質(zhì)和抗氧化水平影響（英文）

1、Postharvest Biology and Technology 44 (2007) 107–115Postharvest hot air treatment effects on the antioxidant system in stored mature-green tomatoesElhadi M. Yahia a,?, Gloria Soto-Zamora b, Jeffrey K. Brecht c, Alfonso G

2、ardea ba Universidad Aut´ onoma de Quer´ etaro, Juriquilla, Quer´ etaro 76230, Qro., Mexico b CIAD, Hermosillo, Sonora, Mexico c Horticultural Sciences Department, University of Florida, Gainesville, FL, U

3、SAReceived 28 September 2005; accepted 26 November 2006Abstract‘Rhapsody’ tomatoes were exposed to air at 20 (control), 34 or 38 ?C, and 95% RH for 24 h and then stored at 4 ?C or 20 ?C for up to 4 weeks. Fruit exposed t

4、o 34 or 38 ?C and stored at 20 ?C had higher cysteine, “reduced glutathione”, catalase, and glutathione S-transferase, but lower isoascorbic acid and ascorbate peroxidase compared to control fruit. Fruit exposed to 38 ?C

5、 developed slight heat injury, and had slightly lower ?-carotene, lycopene, cysteine, ascorbate peroxidase, catalase, and “reduced glutathione” compared to fruit exposed to 34 ?C. Fruit stored at 4 ?C had less color deve

6、lopment, lower ?-carotene, lycopene, ascorbic acid, isoascorbic acid, dehydroascorbic acid, cysteine and “reduced glutathione”, and higher ?-tocopherol, dehydroascorbate reductase, peroxidase, catalase, and glutathione r

7、eductase than those stored at 20 ?C. Of the two heat treatments, 34 ?C for 24 h caused little injury, and had less negative effects on antioxidants during storage at 4 or 20 ?C than did prior exposure to 38 ?C. © 20

8、06 Elsevier B.V. All rights reserved.Keywords: Lycopersicon esculentum; Heat injury; Chlorophyll; Carotenoids; Lycopene; Ascorbic acid; Tocopherol; Glutathione; Cysteine; Enzymes1. IntroductionTomato fruit are sensitive

9、to chilling, and fruit harvested mature-green may develop chilling injury (CI) if held below 13 ?C for 2 weeks or longer (Soto et al., 2005). Heat treat- ments have been proposed to ameliorate CI, in addition to causing

10、other positive effects such as control of ripening, and control of decay and insects in several fruits and vegetables (Yahia and Ortega, 2000). Lurie and Sabehat (1997) reported that 2 d at 38 ?C prior to 2 ?C storage el

11、iminated CI symp- tom development in ‘Daniella’ tomatoes for up to 4 weeks without causing any heat injury. Similarly, McDonald et al. (1998) reported that 2 d exposure to 38 ?C allowed mature- green ‘Sunbeam’ tomatoes t

12、o ripen normally without CI after 2 weeks at 2 ?C. However, it is important to study the effect of these heat treatments on some important nutritional and health components, such as antioxidants.? Corresponding author. T

13、el.: +52 442 2281416; fax: +52 442 2281416. E-mail address: yahia@uaq.mx (E.M. Yahia).Various biochemical and physiological alterations have been associated with heat treatments (Klein and Lurie, 1991). Chlorophyll conte

14、nt in apple peel, plantain peel and tomato pericarp decreased during a hot air treatment of 35–40 ?C (Seymour et al., 1987; Lurie and Klein, 1991), and treatment with hot air at 38 ?C inhibits lycopene synthesis in tomat

15、oes (Cheng et al., 1988). Thermal processing was found to elevate total antioxidant activity and bioaccessibile lycopene content in tomatoes, and produced no significant changes in total phenolics and total flavonoids co

16、ntent, although loss of Vita- min C was observed (Dewanto et al., 2002). Heat treatment (37 ?C for 3 d) induced 2.5-, 1.2-, and 1.4-fold increases in theactivitiesofcatalase,ascorbateperoxidaseandsuperoxide dismutase, re

17、spectively (Sala and Lafuente, 1999). Antioxi- dant activity of citrus peel extracts was significantly affected by heating temperature (50–150 ?C) and duration treatment (10–60 min) (Jeong et al., 2004). Oxidative damage

18、 is considered to be an early response of sensitive tissues to chilling (Hariyadi and Parkin, 1991). It has been reported that chilling elevates the level of active oxygen0925-5214/$ – see front matter © 2006 Elsevi

19、er B.V. All rights reserved. doi:10.1016/j.postharvbio.2006.11.017E.M. Yahia et al. / Postharvest Biology and Technology 44 (2007) 107–115 109with 3.5 ?m C18 symmetry column (4.6 mm × 150 mm) and diode array detecto

20、r at 294 nm (Soto et al., 2005). The mobile phase used was methanol (100%) at 8.3 ?L s?1. Cysteine and reduced (GSH) and oxidized glutathione (GSSG) contents were determined using the method of Farris and Reed (1987) wit

21、h some modifications. Samples (0.25 g per fruit) of freeze-dried tissue were homogenized in 2.5 mL of an aqueous solution containing 10% perchlo- ric acid and 1 mM bathophenanthroline disulfonic acid. The homogenates wer

22、e centrifuged at 7800 × g for 20 min at 4 ?C, and the supernatant collected. The pellet was re-suspended using the same extraction process, the super- natants were combined, and 0.5 mL of the extract and 50 ?L ?-glu

23、tamyl-glutamate (0.5 mM, as internal standard) were carboxymethylated with 50 ?L 100 mM iodoacetic acid dis- solved in 0.2 mM m-cresol purple, and that solution was brought to pH 9–10 by the addition of 0.48 mL KOH (2 M)

24、–KHCO3 (2.4 M) mixture, and was incubated in the dark for 15 min. Samples were then derivatized with 1 mL of 1% 2,4-dinitro-1-fluorobenzene and kept in the dark at 4 ?C overnight. The following day, the samples were cent

25、rifuged at 13,000 × g for 15 min and finally were filtered through a 0.2 ?m Nylon filter before injection in the HPLC. The mobile phase “A” contained 80% methanol and “B” was prepared by adding 800 mL of a solution

26、containing 1 kg sodium acetate, 448 mL H2O, and 1.39 L glacial acetic acid to 3.2 L 80% methanol. The HPLC run started with 80% of “A”, and 20% of“B”for5 min,followedbya10 minlineargradientto1%of “A”, and 99% of “B”, and

27、 2 min after maintaining the mobile phase in that condition it was returned to the initial condition over a 5 min linear gradient and maintained there for 15 min for re-equilibration of the column (Soto et al., 2005). Sa

28、mples of 50 ?L were injected into a 5 ?m Allsphere amino column (250 mm × 4.6 mm) at 16.7 ?L s?1, and the absorbance was read at 365 nm. For dehydroascorbate reductase (DHAR) activity, 0.15 g freeze-dried tissue sam

29、ples were homogenized with 2.5 mL potassium phosphate buffer (100 mM, pH 7.0) containing 0.1 mM EDTA and 1% PVP, and centrifuged at 15,000 × g for 20 min. The reaction medium contained 1.45 mL potas- sium phosphate

30、buffer (50 mM, pH 7.0), 200 ?L of GSH (5 mM), 200 ?L dehydroascorbic acid, and 150 ?L enzyme extract. The absorbance was read at 265 nm, and activity expressed in terms of ascorbic acid production as difference in absorb

31、ance s?1 kg?1 protein (Soto et al., 2005). For ascorbate peroxidase (AsP) activity, 0.15 g freeze- dried tissue samples were homogenized with 2.5 mL sodium citrate buffer (0.1 M, pH 6.0) and centrifuged at 16,000 ×

32、g at 0 ?C for 20 min. The reaction medium contained 500 ?L sodium phosphate buffer (0.1 M, pH 6.1), 500 ?L ascor- bate (1 mM), 880 ?L H2O, and 250 ?L enzyme extract; the reaction was started by adding 20 ?L H2O2. Absorba

33、nce was followed at 290 nm in a Beckman DU-65 spec- trophotometer, and activity was expressed in terms of oxidized ascorbate as mmoles s?1 kg?1 protein (Soto et al., 2005).For determining peroxidase (POD) activity, 0.15

34、g freeze- dried tissue samples were homogenized with 2.5 mL sodium phosphate buffer (0.05 M, pH 7.0), and centrifuged at 9800 × g for 15 min. The reaction medium contained 2.855 mL sodium phosphate buffer (0.05 M, p

35、H 6.0), 45 ?L guaiacol (1%), 40 ?L H2O2 (0.3%), and 60 ?L enzyme extract.Theabsorbancewasrecordedat470 nminaBeckman DU-65 spectrophotometer, and activity expressed in terms of tetraguaiacol production as mmoles s?1 kg?1

36、protein (Soto et al., 2005). For catalase (CAT) activity, 0.15 g freeze-dried tissue sam- ples were homogenized with 2.5 mL potassium phosphate buffer (100 mM, pH 7.5) and centrifuged at 12,100 × g for 25 min. The r

37、eaction medium contained 2.915 mL potassium phosphate buffer (100 mM, pH 7.0), 80 ?L enzyme extract, and 5 ?L H2O2. The absorbance was recorded at 240 nm in a Beckman DU-65 spectrophotometer, and activity expressed in te

38、rms of H2O2 consumption as mmoles s?1 kg?1 protein (Soto et al., 2005). For superoxide dismutase (SOD) activity, 0.15 g freeze- dried tissue samples were homogenized with 2.5 mL potassium phosphate buffer (50 mM, pH 7.5)

39、 containing 1% PVP, and centrifuged at 13,100 × g for 15 min. The reac- tion medium contained 400 ?L potassium phosphate buffer (0.2 M, pH 7.5), 50 ?L 10?4 M EDTA, 2.40 mL 10?6 M cytochrome C2, and 150 ?L enzyme ext

40、ract. The absorbance was recorded at 550 nm in a Beckman DU-65 spectropho- tometer, and activity expressed in terms of difference in absorbance s?1 kg?1 protein (Soto et al., 2005). For glutathione reductase (GR) activit

41、y, 0.15 g freeze- dried tissue samples were homogenized with 2.5 mL potassium phosphate buffer (0.1 M, pH 7.0) containing 1 mM EDTA, 0.1 mM 2-mercaptoethanol, 0.5% Triton X-100, and 2% PVPP, and centrifuged at 17,400 

42、15; g for 20 min. The reac- tion medium contained 1.00 mL potassium phosphate buffer (0.2 M, pH 7.5), 150 ?L of NADPH (2 mM), 150 ?L 20 mM oxidized glutathione, 100 ?L enzyme extract, and 600 ?L H2O. The absorbance was r

43、ecorded at 340 nm, and activ- ity was expressed in terms of NADPH dehydrogenation as difference in absorbance s?1 kg?1 protein (Soto et al., 2005). The extraction of glutathione S-transferase (GST) was similar to that of

44、 GR. The reaction medium contained 1.585 mL potassium phosphate buffer (0.1 M, pH 7.0) containing 1 mM EDTA, 15 ?L 150 mM CDNB (1-cloro- 2,4-dinitrobenzene), 100 ?L 75 mM reduced glutathione (GSH), and 300 ?L of enzyme e

45、xtract. The absorbance was recorded at 340 nm, and activity was expressed in terms of 2,4-dinitrophenyl S-glutathione formation as difference in absorbance s?1 kg?1 protein (Soto et al., 2005). Protein analysis was deter

46、mined according to Bradford (1976) on fresh or freeze-dried tissue (depending on assay) using bovine serum albumin as the standard. Statistical significance was determined by analysis of vari- ance (p < 0.05) and mean