Identification and quantification of the factors influencing sulphur dioxide residue levels in South African export litchi fruit.

摘要

Pre-export spot checks of fumigated fruit in South Africa have exposed considerable variation in sulfur residue levels of different consignments. A study was therefore launched to determine the most important environmental and fruit physiological causes of the observed variation in sulfur dioxide residue levels. Observations were made directly after fumigation as well as during sea export and shelf life periods. Sulfur residues are considerably higher in the cultivar McLean's Red than in HLH Mauritius. The residue level is increased when incorporating an acid dip. Another important observation made was that the sulfur dioxide levels on the aril of the fruit increased with advancing maturity while residues on the peel decreased co-equally. The relationship between ambient temperature and relative humidity during fumigation was also quantified. The increased ambient temperature in combination with decreased humidity was found to increase the residue level considerably. A further important observation made was that the practice of leaving fruit overnight before fumigating leads to increased residue levels.