Sodium Bicarbonate Reduces Postharvest Decay Development Of Sandia

Abstract
Sodium bicarbonate (SBC) inhibited in vitro mycelial growth of A. ulternata, Fusurium spp. and R. stolonijkr. SBC action was fungistatic rather than fungicidal. Coating commercially harvested ‘Galia’ and ‘Ein-Dor’ melons with wax containing 2’s) SBC reduced decay incidence after storage and shelf life simulation by four to seven-fold, to a commercially acceptable level of 6&7X, comparedto untreated or waxed-treated controls. This treatment also maintained the fresh and blemish-free appearance of the fruit at harvest. Higher concentrations of SBC (3%) were phytotoxic and significantly reduced general fruit appearance. A trial shipment by sea transport to Europe demonstrated that 2% SBC incorporated into a wax coating maintained the marketability of ‘Galia’ melon fruits comparedto that of untreated fruit. SBC can be an alternative biocide to the fungicide imazalil, thus eliminating unwanted residues on melon fruits. 0 1997 Elsevier Science B.V.
Keywords: Cwumis melo

var.

reticulatus;

Disease

control;

NaHCO,;

Allyl-1-2,4-Chlorophenyl-2-imidazol-l-

ylethylether

1. Introduction Both ‘Galia’ and ‘Ein-Dor’ melon (Cucumis melo var. reticulatus)cultivars are susceptible to the decay-causing fungi Alternaria alternata (Fr.) Keissler and Fusarium spp. , while ‘Ein-Dor’ is * Corresponding author. Fax: + 972 3 9683622/9604428; e-mail: VTALMBPH@VOLCANI.AGRI.GOV.IL

also very susceptible to Rhizopus stolonifer (Ehr. Ex. Fr.) Lind (Barkai-Golan, 1981). Until recently, melons have been treated in the packhouse with a wax containing 2000 pi/l imazalilto control decay development during prolonged storage (Aharoni et al., 1992). However, this treatment leaves a residue of 3-5 mg/kg of imazalil on the fruit, an amount that exceeds the 0.5 mg/kg maximum permissible level (Anonymous, 1990).

0925-5214’97/$17.00 Q 1997 Elsevier Science B.V. All rights reserved. PI1 SO925-5214(97)01412-9

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Y. Aharoni et al. /Postharvest

Biology andTechnology 10 (1997) 201-206

Alternative substances which are safe, effective and economical are needed to control post harvest diseases. Bicarbonate salts are widely used in the food industry at levels of up to 2% for leavening, pH-control, taste and texture development (Lindsay, 1985) and also have broad-spectrum antimicrobial activity (Miyasaki et al., 1986; Corral et al., 1988). The potentialof bicarbonate salts for the control of post harvest pathogens has been demonstrated in citrus (Arimoto et al., 1977), carrot (Punja and Gaye, 1993), and bell pepper (Fallik et al., 1997). The objective of the present work was to determine the effectiveness of sodium bicarbonate in controlling fungal decay on two melon cultivars during prolonged storage and shelf life.

2.2. In vivo tests‘Galia’ melons (Cucumis melo var. reticulatus) were picked in the autumn of 1994 and the spring of 1995 at Ein-Tamar in the Arava desert region of Israel. ‘Ein-Dot-’ melons were picked in the summers of 1993 and 1994 at Kibutz Yifat in the Yizrael Valley. Six melons each were packed in cartons, and transferred to Bet-Dagan where they were randomly divided into groups of five cartons (30 melons) pertreatment. The fruits were removed from the cartons and hand-sprayed until completely coated with Zivdar wax (SafePack, Raanana), designed specifically for melons. The wax contained 1, 2 or 3% SBC (w/v), or 2000 pi/l (active ingredient) imazalil (imazalil sulphate 50%, Allyl- 1-2,4-Chlorophenyl-2-imidazol- lJanssen, ylethylether). After spraying and drying at ambient temperature, the melons were repackedin the cartons and stored for 14 days at 3°C and 4 additional days of shelf life at 20°C (corresponding to sea freight delivery from Israel to Europe and retail marketing). The relative humidity at both temperatures was 85%. Fruit quality was evaluated after storage and shelf life according to the following parameters: General appearance: This was evaluated visually, with regard to the...