Effects of polyethylene bags, ethylene absorbent and 1-methylcyclopropene on the storage of Japanese pears AbstractStorage of the 'Nijisseiki' cultivar of Japanese pears was studied over three seasons for periods up to 36 weeks at 0°C. Storage in 50 pm thick low-density polyethylene (LDPE) bags at 0°C considerably delayed yellowing in all experiments, even after fruit was removed to 20°C for 1 week at the end of storage. The addition of an ethylene absorbent made from potassium permanganate on aluminium oxide (Purafil II) further delayed yellowing. Carbon dioxide levels in both treatments varied, but were generally in the range 2-3%. Oxygen levels remained high, generally 16-19%. In bags without Purafil, ethylene levels rose slightly during storage and were generally about 0.15 pi I 1. When Purafil was included in the bags, the ethylene level was reduced 10-fold or more. A sensory test indicated that the use of LDPE bags and ethylene absorbent resulted in fruit with better eating quality than fruit stored in air. Disorders over the 3-year investigation were low even after long-term storage. The use of polyethylene bags reduced the severity of flesh browning, and flesh spot decay was virtually absent. Tire use of bags increased the severity of core browning. Inclusion of an ethylene absorbent in bags reduced the severity of disorders, particularly core browning. Treatment of the fruit with 1 -methylcyclopropene (1-MCP), before or during storage, resulted in higher ethylene levels in the polyethylene bags. At the concentrations used, 1-MCP did not improve the storage of 'Nijisseiki' compared to the use of polyethylene bags with Purafil II. SUMMARY Storage of the 'Nijisseiki' cultivar of Japanese pears was studied over three seasons for periods up to 36 weeks at 0°C. Storage in 50 pm thick low-density polyethylene (LDPE) bags at 0°C considerably delayed yellowing in all experiments, even after fruit was removed to 20°C for 1 week at the end of storage. The addition of an ethylene absorbent made from potassium permanganate on aluminium oxide (Purafil II) further delayed yellowing. Carbon dioxide levels in both treatments varied, but were generally in the range 2-3%. Oxygen levels remained high, generally 16-19%. In bags without Purafil, ethylene levels rose slightly during storage and were generally about 0.15 pi I 1. When Purafil was included in the bags, the ethylene level was reduced 10-fold or more. A sensory test indicated that the use of LDPE bags and ethylene absorbent resulted in fruit with better eating quality than fruit stored in air. Disorders over the 3-year investigation were low even after long-term storage. The use of polyethylene bags reduced the severity of flesh browning, and flesh spot decay was virtually absent. Tire use of bags increased the severity of core browning. Inclusion of an ethylene absorbent in bags reduced the severity of disorders, particularly core browning. Treatment of the fruit with 1 -methylcyclopropene (1-MCP), before or during storage, resulted in higher ethylene levels in t...
The ‘Nijisseiki’ cultivar of Japanese pears (Pyrus pyrifolia) is also known as nashi in Australia. Nashi were exposed to levels of <0.005, 0.01, 0.1 and 1.0 µL/L of ethylene in air during 26 weeks storage at 0°C. Levels of ethylene as low as 0.01 µL/L increased chlorophyll loss and visual green colour. Increasing ethylene levels also increased softening and internal browning, although flesh spot decay was reduced in the presence of ethylene. While it would be worthwhile to remove ethylene during long-term storage of ‘Nijisseiki’ in air, another alternative, adding 2% carbon dioxide to the atmosphere, is suggested as a possible low cost means to overcome the ripening effect of ethylene.
Nashi cv. Nijisseiki was coated with canola oil before storage at 0°C over 3 consecutive seasons. This resulted in greater retention of green colour, even after only 8 weeks of storage. This effect continued throughout the 40-week storage period and after 1 week at 20°C. Physiological disorders were generally low. The internal atmosphere was measured during storage at 0°C. The mean carbon dioxide levels for control and treated fruit were approximately 0.5 and 1.9%, and oxygen levels were 20 and 13%, respectively. The mean ethylene levels were approximately 5 and 30 μL/L, respectively. Thus, in oiled fruit, increased carbon dioxide levels may have overcome the effects of increased levels of ethylene. When fruit was transferred to 20°C, carbon dioxide and ethylene levels rose and oxygen levels fell but no damage was evident at the lower oil concentrations. Non-oiled fruit was then stored in polyethylene bags with or without a carbon dioxide absorbent (Calcium hydroxide) and an ethylene absorbent (Purafil). Fruit stored with the former became as yellow as the control fruit in air, whilst fruit with Purafil remained greener than fruit held in bags alone. When the absorbents were used together, much of the fruits’ green colour was lost. Carbon dioxide levels therefore appear to be most important for the retention of green colour, and generally improve storage life. Ethylene removal further improves the retention of green colour in the Nijisseiki cultivar. A storage life of at least 40 weeks at 0°C was achieved with fruit from several sources in 3 seasons. Preliminary recommendations for small-scale hand applications are 1 or 2 drops per 240 g fruit. Commercial trials could involve dipping or spraying with 1–2% oil emulsified with Tween 80.
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