Postharvest calcium chloride treatments do not help to increase shelf-life of bananas.
Perera, A. N. and Karunaratne, A. M.
Fruits .Volume 57, Number 2, 2002. Pages 87-94.
2002
บทคัดย่อ
Calcium chloride (CaCl2) treatment has been shown to increase the shelf-life of fruits, mainly through making cell walls less accessible to pathogens and softening enzymes. Bananas of four cultivars, Ambon (AAA), Embul (AAB), Kolikuttu (AAB) and Seenikehel (ABB), were dipped in or pressure infiltrated with 4% CaCl2. To determine the effect of exogenous ethylene on treated fruits, they were ripened with exogenous ethylene. Ca2+ in cell wall fractions was monitored by atomic absorption spectrophotometry. Cup plate assays were performed to determine pectinase activity. Pressure infiltration accelerated ripening and disease [unspecified], and reduced firmness (P<0.05). However, when exposed to ethylene, CaCl2 pressure-infiltrated bananas were insignificantly firmer than distilled water-infiltrated and ethylene-ripened bananas, showing a significant interaction (P<0.05) between infiltration treatments and ethylene ripening. There was no consistent increase in covalently bound pectin of cell walls as seen in fruits that respond positively to CaCl2. Firmness reduction and ripening acceleration by Ca2+ treatment cannot be explained if polygalacturonase (PG), known to be inhibited by Ca2+, was the dominant pectinase. Enzyme assays gave evidence of PG activity. When ammonium oxalate (known to bind Ca2+) was eliminated from the test medium, pectinase activity increased with increasing pH (pH 5 to 9). The presence of a pectinase enzyme which exhibits activity in the presence of Ca2+ is apparent. Ca2+ does not appear to influence cell wall structure of bananas but appears to influence ripening physiology.