Abstract
Abstract: Pineapple belongs to the genus Ananas in the family Bromeliaceae, which is one of important tropical fruits in China and has the unique flavor people love. Pineapple industry has become an important industry in the development of agricultural economy in the tropical and subtropical regions, and about 60% of them are consumed in the form of fresh fruit in the producing area. However, ripe pineapples are not able to be kept for a long time, and easily suffer softening and blackheart. 1-methylcyclopropene (1-MCP) is a commonly used inhibitor of ethylene receptor, which is specifically and irreversibly bound to ethylene receptors to delay fruit ripening and senescence. Previous research results showed that 1-MCP postponed the softening of climacteric fruits, kept the quality of fruits in storage and extended the shelf life of fruits. Some research reported that 1-MCP inhibited the softening of non-climacteric fruits. Pineapple is a typical non-climacteric fruit and the effect of 1-MCP on pineapple fruit is rarely reported. The purpose of this study was to investigate the effects of 1-MCP treatment on postharvest physiology and quality of pineapple, and provide a theoretical basis for the storage of fresh pineapple. The tested variety was 'Bali' pineapple. Harvested mature fruits were transported to the laboratory immediately, and then the fruits with the same size and being healthy were selected, washed and dried in natural air ventilation for test. Tested pineapple fruits were put into airtight boxes with different 1-MCP concentrations for 12 h at room temperature (25℃), then the fruits were placed in an incubator with about 85% humidity. Fruits treated by air were used as the control. Physiological indices related to fruit quality were evaluated, such as fruit firmness, malondialdehyde (MDA), total soluble solids (TSS), titratable acid (TA), vitamin C (VC) content and ethylene production. Activities of lipoxygenase (LOX), catalase (CAT) and peroxidase (POD) were detected by spectrophotometer. In the experiments, there were 3 replicates with 30 fruits for each repetition, and each treatment had 90 fruits. Statistical analysis of data was performed by the Excel software. Significant differences were analyzed by the statistical product and service solutions (SPSS) software at the level of 0.05. The results showed that the fruit firmness had significant differences between the control and the treatments with different 1-MCP concentrations (0.20, 0.35, 0.45 and 0.60 μL/L) during the storage. On the 8th day, the firmness of fruits treated with 0.20 μL/L 1-MCP was 2.80 kg/cm2 which was similar to that of the control group. With the increase of 1-MCP concentration, the fruit firmness was gradually increased. While the 1-MCP concentration continued to rise up to 0.60 μL/L, the firmness of pineapple fruits and peel color showed no significant difference compared to the treatment with 0.45 μL/L 1-MCP concentration. So, the 0.45 μL/L concentration of 1-MCP was the best concentration to treat pineapple fruits. During the storage, the peak of ethylene production was delayed for 4 d in 1-MCP treated group. From the beginning to the 14th day, the content of MDA of treated fruits slowly increased and was significantly higher than that in the control group. Meanwhile, the activities of LOX in treatment and control groups gradually declined, significantly lower than that in the treatment group during the storage. The peak of POD and CAT activity was also delayed; the activity of all POD, CAT and SOD was higher than the control group, and on the 14th day, the activity was 22.30%, 32.35% and 36.67% higher than the control, so the treatment by 1-MCP could defer the ageing process of pineapple during the storage. The content of TA showed a decline in the control and treated group. But, the TA content of treated fruits decreased slowly compared with the control group. Fourteen days after storage, there were 44.22 mmol/100g TA in the treatment and 33.01 mmol/100g TA in the control group. The determination showed that the soluble sugar content (SSC) was 300.24 mmol/g in the 1-MCP treated pineapple fruits and reached a peak on the 8th day, significantly higher than the peak content of 283.55 mmol/g in the control group on the 6th day. This indicated that the treatment delayed the increase of SSC of 1-MCP treated fruits. The VC content of the 1-MCP treated fruit showed a slow rise within the former 6 days, and after that gradually declined, which was 17.65 mg/100 g on the 14th day, about 44.80% higher than the control group. In summary, under the normal temperature conditions, the 1-MCP treatment postpones the time of ethylene production of pineapple fruits, and effectively delays the postharvest pineapple softening process, the decline of MDA, TA and VC content, and the increase of SSC, POD, CAT and SOD activities. Therefore, the flavor of pineapple fruits can be maintained by the 1-MCP treatment.
DownLoad: