Elsevier

Food Chemistry

Volume 100, Issue 4, 2007, Pages 1385-1392
Food Chemistry

The effect of postharvest calcium application on tissue calcium concentration, quality attributes, incidence of flesh browning and cell wall physicochemical aspects of peach fruits

https://doi.org/10.1016/j.foodchem.2005.11.036Get rights and content

Abstract

The effects of postharvest calcium applications on cell wall properties and quality attributes of peach fruits (Prunus persica L. Batsch, cv. ‘Andross’) after harvest or cold storage up to 4 weeks were determined. The fruits were immersed in deionised water or in different calcium sources (calcium chloride, calcium lactate and calcium propionate) at two calcium concentrations (62.5 and 187.5 mM Ca). Calcium concentration profiles in fruits (peel and flesh), in cell wall and in pectin fractions were determined. The calcium content in the peel increased up to 2.7-fold, whereas flesh calcium increased up to 74%, 1 day after immersion. The increase of flesh calcium was accompanied by increase of cell wall calcium, which corresponded to a significant increase of calcium in the water-insoluble pectin fraction. However, calcium became saturated in the water-insoluble, but not water-soluble, pectin fraction with 62.5 mM Ca treatment. Treatment with 62.5 mM Ca salts was as effective as higher concentrations of calcium chloride maintaining tissue firmness during storage. Inversely, calcium lactate and calcium propionate at high concentrations (187.5 mM Ca) caused toxicity symptoms on the fruit surface, expressed as skin discoloration and superficial pitting, leading to additional chemical changes and reduced tissue firmness. Postharvest calcium applications limited the intense of chilling injury symptoms, expressed as flesh browning after 4 weeks cold storage. Peach fruits with severe flesh browning symptoms were characterized by reduced ethylene production, and reduced activities of the pectin modifying enzymes poly-galacturonase and pectin-methyl-esterase.

Introduction

After harvest rapid ripening in peach fruits is responsible for short shelf life and represents a serious constraint for efficient handling and transportation. Ripening can be retarded by cold storage. However, cold storage life of peaches is frequently limited by chilling injury (CI) and loss of quality (Brummell et al., 2004, Valero et al., 1997). Peach fruits after extended cold storage present symptoms of internal breakdown (IB), expressed as flesh browning (FB) and similar symptoms in other fruits have been attributed to low calcium content (Hewajulige et al., 2003, Thorp et al., 2003).

Preharvest calcium sprays may increase slightly peach fruit calcium content (Crisosto, Day, Johnson, & Garner, 2000) and this increase may differ from year to year, highly regulated by environmental factors (Biggs, A.R., personal communication). Addition of calcium fertilizer to soil is of questionable value (Lester & Grusak, 1999). Conversely, infiltration methods under pressure or vacuum provide a rapid and effective method for increasing calcium content (Lara et al., 2004, Saftner et al., 1998). However, these treatments often cause surface damage (Saftner, Conway, & Sams, 1999).

Postharvest calcium dips can increase calcium content considerably compared to preharvest sprays, without causing fruit injury, depending on salt type and calcium concentration. Postharvest calcium application maintains cell turgor, membrane integrity, tissue firmness and delays membrane lipid catabolism, extending storage life of fresh fruits (Garcia et al., 1996, Picchioni et al., 1998).

Many studies have examined the effects of calcium on fruit firmness and decay after harvest, but few have focused on compositional changes in cell walls of fruits throughout storage (Chardonnet et al., 2003, Saftner et al., 1998). To the best of our knowledge, few data exists regarding the effect of postharvest calcium dips in cell wall physicochemical attributes of peach fruits and it has been mainly focused on qualitative characteristics (Wills & Mahendra, 1989) or fungal resistance (Conway, Sams, & Kelman, 1994).

As well as from calcium chloride, which has been extensively used in fresh fruits (Chardonnet et al., 2003, Saftner et al., 1998), calcium propionate and calcium lactate are proposed as alternative calcium sources (Buta et al., 1995, Saftner et al., 2003). The objectives of this study were to determine the effect of postharvest fruit immersion in different calcium sources and the effect of calcium concentrations on peach fruit tissue and cell wall composition during cold storage.

Section snippets

Plant material

Peach (Prunus persica, cv. ‘Andross’) fruits were harvested at firm-ripe stage from a commercial orchard (Naoussa, Northern Greece) in early morning (fruit internal temperature 23 ± 1 °C). After selection for uniformity of size and freedom from defects, they were divided into 6 lots of 30 fruits for each water and calcium treatment supplemented with wetting agent (0.03% Agral®600). All treatments included immersion for 5 min in deionized water (water temperature = 20 °C) (control) and three calcium

Calcium

Significant increase of calcium content both in the peel and the flesh of calcium-treated peach fruits were recorded. Peel calcium increased by 2.3 to 2.7-fold and flesh calcium increased by 50% to 74% in calcium-treated peach fruits, compared to control fruits, 1 day after immersion (Table 1). Calcium source did not seem to affect calcium absorption. Calcium content was significantly higher in the high concentrations of all calcium sources applied, although it was not proportional to the

Conclusions

Clingstone non-melting peach fruits destined for canning are often stored for several days in cold rooms so that they can be processed gradually, according to the capacities of canning industries. Calcium chloride immersion at 62.5 mM Ca could be suggested as a potential postharvest handling of non-melting peach fruits destined for processing after prolonged cold storage, since it provides fruits with better qualitative characteristics (increased tissue firmness, less susceptibility to

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