The effects of hot-water treatments in combination with cooling and/or storage on the physiology and disease of mango fruits (Mangifera indica Linn.)

Abstract

SummaryThis paper reports three separate studies. The first involved devising an effective phased hot-water disinfestation treatment on the basis of reported lethal time (LT90) values of 5–15 min at 46°C core temperature and heat units. Phased hot-water treatment at 36.5°C for 60 min plus 46.5°C for 43 min (4185 degree minutes) attained and maintained a seed (core) temperature of 46–46.5°C for 5–12 min. The impact of phased hot water was tested against the recommended treatment (46.5°C for 90 min – 4184 degree minutes) and a control, on the basis of fruit colour, taste, flavour firmness and the incidence and severity of diseases, internal and external injury and physiological disorders. Following hot-water treatments, ‘Keitt’ and ‘Tommy Atkins’ mangoes were subjected to an array of treatments including air or hydrocooling, 10 d of storage at 13°C with or without 1 d of intermittent warming at 34°C (sixth day) and 2 d ripening at 22°C respectively as a simulation of possible handling procedures. Phased hot-water treatment and 1 d of intermittent warming resulted in a significantly low incidence and severity of internal and external injury and diseases and low off-flavours compared with control and hot water at 46.5°C for 90 min. The impact of the above hot-water treatment at half heat units previously tested (2092.5 degree minutes) in combination with intermittent warming (34°C) during 12 d of cool storage (13°C) showed that treatment with hot water at 46.5°C for 45 min and 2 d of intermittent warming resulted in a significantly low incidence and severity of external injury and diseases, softer fruits, higher °Brix and better general appearance. The incidence of disease was influenced by pre-harvest factors and the effects of hot-water treatments on fruit quality was dependent on time/temperature combinations and not on total heat units received. Intermittent warming advanced fruit ripening.