Market quality of guavas after hot-water quarantine treatment and application of carnauba wax coating
1997
McGuire, R.G.
Immersion of guavas (Psidium guajava L.) for 35 min in water at 46.1 +/- 0.2 degrees C slowed softening, sweetening and color development of fruit and delayed ripening by 2 days. Heat treatment also increased susceptibility to chilling injury, decay, and weight loss in storage, but overall loss of quality was minimal. Waxing fruit within 90 min of heat treatment exacerbated chilling injury, further delayed ripening with a concomitant increase in the percentage of fruit not ripening, and caused fruit to remain greener. Waxed fruit had a lower acidity and soluble solids concentration and did not appear to ripen normally. Although heating did not appreciably affect the percentage of fruit that failed to ripen, the combination of heating and nearly immediate waxing increased the proportion not ripening to 45%. Heat and wax treatments, alone or in combination, caused CO2 levels to increase significantly before the initiation of ripening but waxing also reduced the O2 content of fruit at this time. Before ripening, O2 levels were inversely correlated (r less than or equal to -0.950) with injury, firmness, date and percentage of fruit ripening, and pH and directly correlated (r greater than or equal to 0.950) with peel color and the concentration of acids and sugars in the pulp. Delaying the waxing of heat-treated guavas or reconditioning them for 24h at 20 degrees C before cold storage promoted normal ripening and helped to maintain the quality of heat-treated fruit.
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