Postharvest Dip Research Articles

Post harvest Spoilage of Mangoes by Penicillium cyclopium and its Control by Gamma‐Radiation and a Fungicide

Abstract Penicillium cyclopium has been isolated from spoiled ripe alphonso mango, Spores were found resistant up to a 500 krad dose of γ‐radiation. A 25 krad dose treatment which is normally used for the prolongation of shelf life of mangoes could not protect them against artificial or natural infection. Bavistin (2‐(methoxy carbamoyl)‐ benzimidazole) inhibited completely spore germination at a concentration of 100 mg/1. A post harvest dip of unripe mangoes into an aqueous solution of this fungicide lowered the degree of spoilage considerably.

Bitter-pit incidence and changes in Ca 2+ content in apple after post-harvest dip in CaCl 2 or GA 3

‘Maygold’ apples were dipped in CaCl 2 or GA 3 as post-harvest treatments. Bitter pit was reduced by CaCl 2 and GA 3. Pitted fruits always had low Ca 2+ levels. The cellular fractionation of the flesh tissue of untreated apples showed a negative correlation between soluble Ca 2+, acid labile Ca 2+ and bitter pit. An increase of Ca 2+ in these fractions by means of CaCl 2 treatments did not prevent the disorder. GA 3, at the more effective concentration for protecting fruits, increased the soluble Ca 2+ of pitted flesh tissue. The possibility that the disorder is linked to an alteration of the Ca 2+ transport mechanism at cell level is suggested as a plausible explanation.

Benomyl residues in litchis after post-harvest dipping

Benomyl residues in litchis were determined at 2, 5, 9 and 15 d after a commercial postharvest dipping treatment at a level of 422 mg/litre. Residues were analysed in skin and flesh separately with 1.3 mg/kg benomyl being the highest flesh residue and 20.6 mg/kg the highest skin residue (average values from duplicate determinations). The benomyl levels showed no significant difference with time (P> 0.05) in either flesh or skin. Residues are also reported for a double recommended strength treatment. After consideration of these data the relevant authorities have set a maximum residue limit of 10 mg/kg for benomyl in litchi.

Regulation of ripening by chemicals in ‘Alphonso’ mango

Post-harvest dip treatment of ‘Alphonso’ mango with cycocel, alar, gibberellic acid and menadione bisulphite significantly retarded ripening, as judged by the number of ripe fruits, during storage at 28°C. However, after cycocel treatment, retardation of ripening was observed in the early part of storage only. The value for the Brix/acid ratio was low and that for firmness was high in fruits treated with gibberellic acid and menadione bisulphite, indicating their unripe character. The results suggest that mango ripening can be controlled by the use of chemicals.

Some Effects of Emulsifiable Coatings on Weight Loss, Stem Discoloration, and Surface Damage Disorders in ‘Van’ Sweet Cherries1

Abstract Preharvest antitranspirant sprays were most effective in decreasing the incidence of surface pitting in ‘Van’ sweet cherries (Prunus avium L.) when applied immediately prior to harvest. Antitranspirant or wax coatings applied to ‘Van’ cherries as a postharvest dip decreased weight loss in storage, the incidence of discolored stems and surface pitting in storage. Antitranspirant concentration in the postharvest dipping solution was negatively correlated to the incidence of surface pitting.

Use of calcium to reduce storage breakdown in Spartan apples

Abstract The effects of 0.5% calcium nitrate sprays and 5% calcium chloride post-harvest dips on cool-stored Spartan apples were investigated. Nine sprays applied at intervals over the whole growing season or a post-harvest dip proved equally effective in reducing breakdown. Incorporation of lecithin in the dip prevented skin damage caused by calcium.

PARTIAL CONTROL OF BITTER PIT IN NORTHERN SPY APPLES WITH A POST-HARVEST DIP IN CALCIUM CHLORIDE SOLUTION

Bitter pit of Northern Spy apples that were stored in air and in controlled atmosphere (CA) storage was decreased by a post-harvest dip in 4% CaCl2 solution containing 0.35% Keltrol. The calcium treatment also decreased breakdown, loss of fruit firmness, and loss of fruit acidity, and increased Ca content of apple cortex tissue. There was no fruit injury. The dip treatment increased rots in one instance, presumably from dispersal of fungal spores during the dipping process and not due to an effect of calcium. Absorption of Ca was slightly greater in CA storage than in air storage. Percent of apples with bitter pit (all treatments combined) was positively correlated with K content of leaf tissue, with Mg and K content of undipped fruit cortex tissue and with (K + Mg)/Ca ratios (eq/eq) of leaf and of undipped fruit cortex tissue. Leaf Ca was significantly related to pit when combined with leaf (K + Mg)/Ca in multiple regressions.

Rapid Spectrophotometric Method for Determination of 2-Aminobutane in Postharvest Dips

Abstract A rapid method is described for measuring 2-aminobutane in postharvest dip fluids. Samples of the dip fluid are diluted to bring the 2-aminobutane content in the range 500—5000 μg and reacted with carbon disulfide and cupric ion to form a chloroform-extractable complex measured spectrophotometrically at 430 nm. The accuracy and reproducibility of the method are comparable with the more lengthy modified product and residue methods.

THE EFFECT OF FRUIT SIZE AND METHOD OF CALCIUM CHLORIDE APPLICATION ON FRUIT CALCIUM CONTENT AND BREAKDOWN IN SPARTAN APPLE

Four sprays of 0.6% CaCl2, one spray of 2% or 4% CaCl2, and postharvest dips in 4% CaCl2 each decreased the incidence of breakdown in Spartan apple (Malus pumila Mill.). Fruit Ca levels were significantly increased by each CaCl2 treatment except the 2% CaCl2 spray applied 2 wk prior to harvest. The postharvest dip was more effective in increasing fruit Ca levels and decreasing the incidence of breakdown than the Ca spray applications in one orchard. Combining all three methods of Ca application resulted in the greatest increase in tissue Ca. A 4% CaCl2 spray or dip caused some injury to fruit from one orchard. Increases in fruit Ca content as a result of sprays or dips were consistently greater in fruit from one orchard than the other.

SOME FACTORS AFFECTING UPTAKE OF CALCIUM BY APPLES DIPPED AFTER HARVEST IN CALCIUM CHLORIDE SOLUTION

An inverse relationship occurred between fruit weight and increase in calcium (Ca) content in Spartan apples (Malus pumila Mill.) resulting from postharvest CaCl2 dips. The influence of fruit weight on Ca increase was greatest in tissue near the core. The addition of a thickener to the dip solution resulted in significantly higher flesh Ca levels. Ca absorption was significantly enhanced by treating with dip solutions which were colder than the fruit. Spartan apples absorbed less Ca from a postharvest CaCl2 dip than did McIntosh which absorbed less than Golden Delicious or Delicious. The use of a surfactant in the CaCl2 dipping solution did not affect Ca penetration into McIntosh or Delicious apples but decreased penetration of Ca into Spartan and Golden Delicious.

Uptake of Calcium by Apples from Postharvest Dips in Calcium Chloride Solutions1

Abstract Uptake of Ca by apples (Malus domestica Borkh.) from a postharvest dip in CaCl2 solutions increased as CaCl2 concentration in the dip solution increased up to 3-4%; a 4% solution increased flesh Ca level by 60 to 100 ppm after 3 months of storage. Uptake occurred primarily during storage, apparently as Ca from residues left by the dipping treatment diffused through openings in the fruit surface. Absorbed Ca remained largely near the fruit surface, although some deeper penetration occurred. Uptake from a 2% CaCl2 solution was not influenced significantly by thickener, surfactant, fungicide, or scald inhibitor in the dip solution, and was not consistently influenced by storage at relative humidities of from 90% to greater than 95%. When relative humidity had an effect, uptake was reduced at concentrations greater than 95%. A 4% CaCl2 dip treatment reduced softening and development of senescent breakdown in ‘McIntosh’, but did not significantly modify quality of ‘Cortland’ or ‘Baldwin’ apples.

Evaluation of the use of butylated hydroxytoluene to reduce superficial scald of apples

Butylated hydroxytoluene (BHT) was found to be effective in reducing the incidence of superficial scald in ‘Granny Smith’ apples grown in Australia and New Zealand, when it was applied to the fruit as a post-harvest dip or when the fruit were stored in wraps impregnated with BHT. However, much higher concentrations of BHT were required to produce an equivalent reduction in scald compared with diphenylamine or ethoxyquin.

Softening of ‘McIntosh’ Apples Reduced by a Post-harvest Dip in Calcium Chloride Solution plus Thickener1

Abstract Softening of ‘McIntosh’ apples (Malus domestica Borkh.) during storage was reduced by dipping fruit 2 days after harvest in 4% CaCl2 solution (40 g of commercial CaCl2 in 1 liter of water). The addition of Keltrol, a commercial food thickener, at 3 g/liter to retain more Ca solution on the fruit increased the effectiveness of the treatment. After 4 months storage at 0°C, fruit treated with CaCl2 and with CaCl2 plus Keltrol was 0.30 and 0.56 kg firmer by the pressure test than untreated fruit.

The influence of some packaging and post-harvest treatments on the incidence of Ripe Spot in ‘Golden Delicious’ and ‘Crofton’ apples

A trial was designed to study different methods of high humidity storage for bushel packs of apples. The methods studied were polyethylene (= polythene) bag liners (= polyliners), perforated polythene lined, together with the effectiveness of thiabendazole (T.B.Z.) in controlling Ripe Spot ( Gloeosporium sp.) in polythene lined packs. A further treatment incorporated a wax coating on the apples instead of a polythene liner. A post-harvest dip of T.B.Z. followed by storage in polylined packs ensured that ‘Golden Delicious’ and ‘Crofton’ apples had minimal weight losses and low levels of Ripe Spot. Storage in polythene liner or perforated polythene liner without T.B.Z. resulted in high levels of Ripe Spot in both cultivars. Although waxing prior to storage did not increase the incidence of Ripe Spot over that in control fruit, it did not reduce weight loss to the low levels of the polylined treatments.

Control of spoilage and ripening in mango fruit by zineb and sodium diethyldithiocarbamate

AbstractZineb (0.375%) in hot water as a post harvest dip reduced the spoilage due to fungi and delayed the ripening process in Alphonso and Pairi mangoes. Spoilage was minimal when the treatment was given soon after harvest. Sodium diethyldithiocarbamate (0.4 %) was also effective in reducing the spoilage in Pairi mangoes although the treatment was delayed until 7 days after harvest. These compounds did not adversely affect the chemical composition or edible quality of the fruit.

Behaviour of thiabendazole when used as a post-harvest dip in banana packing sheds

A series of trials was undertaken to study the behaviour of a thiabendazole wettable powder, when used as a post-harvest treatment for the control of squirter and blackend diseases in bananas packed as 'singles' in wooden boxes. In three grower sheds box lots of 100 were dipped in a range of fungicide concentrations, under conditions that could be expected to differ from those in a centralized packing shed. There was an apparent depletion of thiabendazole, the depletion rate being highest in the initial stages of dipping and after topping, and over all trials each 25 cases treated appeared to reduce concentration by approximately 21 per cent. Topping up appeared to cause a sudden rise in thiabendazole concentration. Fruit skin deposits decreased significantly (P < 0.001 ) as concentration decreased and were 0.8 p.p.m. for a dip at 110 p.p.m. and 1.4 p.p.m, for one at 400 p.p.m. No phytotoxic effects were observed on either green or ripe fruit, and ripening abnormalities were absent. The trials indicated that with an initial concentration of about 200 p.p,m. and using a recommended dip management procedure, a grower should be able to treat 100 boxes in any one lot of dip and effectively control the major post-harvest fruit rots.

Control of superficial scald on Granny Smith apples with diphenylamine

The preliminary work of Smock (1955) indicated that treatment of apples with diphenylamine (DPA) offered a promising new method of controlling superficial scald on cool-stored apples. The effect of DPA and various methods of application hare been widely studied under Australian conditions over five seasons, Granny Smith apples grom-n in New South Wales being used. Treatment of fruit with a suitable concentration of DPA prevented the development of scald on fruit cool-stored in air, in controlled atmospheres, and in polyethylene film box liners, even when scald was severe and not controlled by oiled wraps. DPA was successfully applied to the fruit by impregnating it into standard paper wraps, by post-harvest dipping, and by pre-harvest spraying. It was found that there was a quantitative relation between the severity of scald and the concentration of DPA required to control it. DPA was shown to have a very limited mobility in the fruit. Residues in the fruit were related to both the amount applied and the method of application, and in all cases were low after cool storage. DPA appears to have a sufficiently low phytotoxicity for use as a pre-harvest spray. Its human toxicity is still under investigation. If approved for use on apples it will probably be in a purified form.