Abstract
Experiments were conducted to observe the effect of pre-harvest calcium (Ca) applied as calcium chloride (1% W/V) and postharvest hot water treatment (HWT) on “Royal Delicious” apples. For this, apples were divided in 4 lots viz., untreated (neither Ca nor HWT), Ca alone (pre-harvest 3 sprays of CaCl2 (1.0% w/v) in the orchard), HWT (42℃ for 2 h). Apples of all four lots were stored in cold storage maintained at 0℃ ± 1℃ and 90% - 95% relative humidity for 6 months. After storage, fruits were removed to ambient conditions for 5 days, and then observations on decay area and incidence, bitter pit incidence, fruit Ca content, lipoxygenase (LOX) and antioxidant (AOX) activity, fruit firmness and fruit quality parameters were recorded. After 6 months in cold storage plus 5 day at 22℃ ± 2℃ and 70% + 4% RH, apples, which received Ca as pre-harvest spray or those which received postharvest hot water treatment or Ca + HWT had significantly lesser decay area (decay lesions) caused by Penicillium expansum or Botrytis cinerea than untreated ones (control). Ca + HWT treatment was significantly more effective on B. cinerea than P. expansum. Untreated apples exhibited higher incidence of bitter pit (18.2%) than those treated with Ca or HWT or both. Fruit Ca content (2.92% DM) were significantly lower and conversely the LOX activity (6.9 μmoles min–1×g–1FW) was higher in untreated apples. Similarly, total phenolics and AOX activity were also lower in the untreated apples than Ca or HWT treated. HWT or Ca treated apples have beneficial effects on fruit firmness, peel colour and quality parameters like TSS and ascorbic acid content. Thus, it is concluded that pre-harvest sprays of calcium chloride with postharvest HWT is highly useful for “Royal Delicious” for reducing decay loss, maintaining firmness, high levels of antioxidants and fruit quality.
Highlights
Apple (Malus x domestica Borkh) is the most important temperate fruits of the world
The total phenolic content of the apples were determined by the method of Singleton and Ross [14] method with some modifications. 5 g fruit was crushed in 10 ml of 80% ethanol and centrifuged
After 6 months in cold storage plus 5 day at 22 ̊C ± 2 ̊C and 70% + 4% RH, apples, which received Ca as preharvest spray or those which received postharvest hot water treatment (42 ̊C for 2 h) or their combination had significantly lesser decay area caused by Penicillium expansum or Botrytis cinerea than those which were not treated at all
Summary
Apple (Malus x domestica Borkh) is the most important temperate fruits of the world. Several varieties are grown commercially but “Royal Delicious” dominates others in almost every country [1]. Conway et al [5] reported additive effect of heat treatments (38 ̊C for 4 days) and infiltration of calcium chloride (3%) on reducing decay and maintaining quality of “Golden Delicious” apples. Combining the 2 treatments, prestorage heat and Ca dip, gives additional benefit over either alone in maintaining fruit firmness [8] or reducing storage disorders [5] In all these studies, apples were exposed to hot water at 38 ̊C for 4 - 6 days or 42 ̊C for 2 days. Considering the usefulness of hot water treatment and Ca in several parts of the world, we undertook this study with the objective to observe the additive effects, if any, of pre-harvest Ca sprays with postharvest hot water dip on softening, decay, occurrence of bitter pit and quality of “Royal Delicious” apples during storage
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