Effect of packline hydro-heating treatments on Heidi fruit quality after four weeks of cold-storage.
Oosthuyse S. A.
Author Affiliation: Merensky Technological Services, P.O. Box 14, Duivelskloof 0835, South Africa.
Yearbook - South African Mango Growers' Association 16 : 6-11
Abstract : Hydro-heating treatments, aimed at reducing the sensitivity to chilling injury of the skin of hard-mature Heidi mangoes, were applied to fruits on the day of harvest. Prior to treatment, the fruits were washed in water containing 1% Teepol and then rinsed. The treatments were hydro-heating at 50 or 55°C for 5 or 7 min, with or without the addition of non-scald diphenylamine (DPA) to the heating bath. Controls received no hydro-heating. After treatment, fruits were all dipped in Omega (180 ml/100 litres H2O) for 20 s, waxed, stored at 11° for 28 days and ripened at 20°. Severe heat scald and peripheral browning occurred following treatment at 55°. DPA had little or no apparent effect in reducing heat scald or surface scald (cold temperature skin injury). The incidence of surface scald or lenticel damage was reduced compared with controls by hydro-heating at 50° for 5 or 7 min when DPA was excluded. The incidence of peripheral browning (browning of mesocarp tissue adjacent to the skin) increased with the increase in time or temperature treatment. Internal browning increased with the increase in water temperature and was increased by DPA. The incidence of internal breakdown (jelly seed or soft nose) was low and was apparently unaffected by the treatments. Fruits treated for 5 or 7 min at 50° had the best flavour. After treatment for 5 min, skin coloration increased with the increase in bath temperature, but it decreased with the increase in bath temperature following treatment for 7 min. DPA enhanced skin coloration when added to the water at 55°, but reduced it when added to the water at 50°. The percentage of good quality fruits present on ripening was greatest following treatment for 5 or 7 min at 50°. Hydro-heating at 50° for 5 min is recommended. Furthermore, it is considered very important that Heidi fruits never be exposed to temperatures of less than 11° during or after shipment.