Synergistic effects of modified atmosphere and minimal processing on the keeping quality of pre-cut papaya (Carica papaya L.)

Abstract

SummaryPre-cut papaya is a highly perishable product and requires suitable pre-treatment and storage protocols for commercial utilisation. Papaya was peeled, cut into slices (5 cm 0.6 cm 0.7 cm) and surface sanitised with chlorinated water (0.1 g l–1). The slices were then subjected to minimal processing pre-treatments with a tissue firming agent (1 g l–1 CaCl2) for 10 min, anti-microbials (0.4 g l–1 potassium sorbate and 0.4 g l–1 sodium benzoate) and anti-browning agents (0.2 g l–1 ascorbic acid) for 30 min, followed by acidification (7.0 g l–1 citric acid) for 2 min. The pre-treated slices were kept under UV light (2.5 kJ m–2 for 10 min) and subsequently packed in a modified atmosphere (3% O2 + 6% CO2 + 91% N2) under partial vacuum (30 kPa), or in air, in polyethylene (PE) pouches (12 cm 10 cm; 25 µm thick; 100 g fill-weight) or in polyethylene terephthalate (PET) bottles (2 l; 500 g fill-weight) with a 2.25 cm2 silicone membrane diffusion window. Samples were stored at 6° ± 1°C and analysed for changes in their physico-chemical, microbiological and sensory attributes, along with their head-space gaseous composition. The pre-treatments acted synergistically with the modified atmospheres to stabilise the papaya slices, physiologically, as well as restricting the proliferation of microbes (e.g., total plate counts of coliforms, yeasts and moulds). Physiological stability was characterised by a significant (P < 0.05) reduction in respiration rate, reduced losses of texture and ascorbic acid, delayed increases in electrical conductivity and in colour co-ordinates, without impeding the sensory quality of the product. Pre-treated papaya slices, kept under different modified atmospheres, had storage lives of 44 – 60 d at 6° ± 1°C, which may facilitate bulk storage and long-distance transportation.