Salvatore D'Aquino

Control of Postharvest Diseases of Fruit by Heat and Fungicides: Efficacy, Residue Levels, and Residue Persistence. A Review

Extensive research has been done in recent years to reduce the heavy dependence on chemical fungicides to control postharvest diseases and disorders of horticultural crops. Alternative strategies were based on improved cultural practices, biological control, plant-defense promoters, and physical treatments such as UV illumination, radiofrequency treatment, heat therapy, and storage technologies. Among these, postharvest heat treatments such as hot water dips, short hot water rinsing and brushing, and hot air conditioning have reduced rot development and enhanced fruit resistance to chilling injury in sensitive cultivars while retaining fruit quality during cold storage and shelf life. Additive or synergistic increases in effectiveness were observed by integrating heat therapy with various chemical compounds, thus leading to significant reductions in the application of active ingredients to protect produce from decay. This paper highlights the knowledge on this topic with emphasis on heat therapy effects and factors affecting the uptake, persistence, and performance of fungicide residues when they are applied in combination with hot water.

Influence of Postharvest Hot Water Treatment on Nutritional and Functional Properties of Kumquat (Fortunella japonica Lour. Swingle Cv. Ovale) Fruit

The present study investigated the influence of a hot water dip (HWD) for 2 min at 50 degrees C, a standard and effective treatment for postharvest decay control of citrus fruit, on the nutritional and health-related properties of kumquats. The results show that most of the parameters examined, including titratable acidity, soluble solids content, maturity index, glucose, fructose, sucrose, ascorbic acid, dehydroascorbic acid, alpha- and gamma-tocopherols, beta-carotene, zeaxantin, rhoifolin, and antioxidant activity, were not significantly affected by treatment. The levels of beta-cryptoxanthin, narirutin, and total flavonoids increased after HWD, whereas lutein and total phenols decreased. The concentration of the essential oil and the relative percentage of the individual components of the essential oil were not affected by HWD except for the minor compound p-menta-1,5-dien-1-ol, which increased after HWD. After storage, lower levels of glucose, total sugars, beta-carotene, beta-cryptoxanthin and lutein were recorded in HWD fruit. A decrease in antioxidant activity and increases in alpha-tocopherol and total vitamin E were found both in control and HWD fruit. The influence of HWD at 50 degrees C for 2 min on individual nutraceuticals and health-related properties was thus generally low and may depend on storage conditions.

Influence of post-harvest treatments with fludioxonil and soy lecithin co-application in controlling blue and grey mould and fludioxonil residues in Coscia pears

The residue levels of fludioxonil (FLU) were determined in Coscia pear following a 1-, 2- or 4-min dip in an aqueous mixture of FLU containing 300 or 100 mg l−1 (active ingredient, a.i.) at 20 and 50°C, respectively, with or without 2% soy lecithin. The efficacy of heat treatment with water and FLU mixtures was investigated on artificially inoculated pears for the control of post-harvest decay caused by blue (Penicillium expansum Link) and grey (Botrytis cinerea Pers. ex Fr.) mould. Treatment with 300 mg l−1 FLU at 20°C increased residues significantly when treatment time rose from 1 to 2 min; no further increase was recorded when dip time raised from 2 to 4 min. FLU residue rates were unaffected by treatment time when 300 mg l−1 a.i. was applied in combination with lecithin at 20°C. While treatment with 100 mg l−1 a.i. at 50°C for 1 and 2 min resulted in similar residue levels, significantly higher residues were detected when dip time increased from 1 to 4 min. Co-application of lecithin significantly decreased FLU residues with respect to fruit treated with FLU alone. Treatments with FLU at 20 or 50°C effectively controlled decay over 10 days of incubation. While co-application of lecithin did not affect the efficacy of FLU at 300 mg l−1and 20°C, treatment efficacy decreased when lecithin was applied in combination with 100 mg l−1 FLU and 50°C for 4 min and to a greater extent when dip time was 1–2 min.

Influence of post-harvest application rates of cyprodinil, treatment time and temperature on residue levels and efficacy in controlling green mould on ‘Valencia’ oranges

The effectiveness of heat treatments with water and cyprodinil in controlling post-harvest green mould caused by Penicillium digitatum was investigated on artificially inoculated ‘Valencia’ oranges. Residue levels of cyprodinil were determined in the oranges as a function of active ingredient concentration, temperature and treatment time. Cyprodinil residues were significantly dependent on treatment time when applied at 600 mg l−1 and 20°C, but not when fruit were treated at 150–300 mg l−1. The application of cyprodinil at 50 or 100 mg l−1 at 55°C for 30 s produced similar residue levels, while residues increased when the application rate was 150 mg l−1. Cyprodinil at 100 mg l−1 and 60°C produced a significant increase in residues compared to treatment at 50 mg l−1; no significant increase in residues was found when the application rate was raised from 100 to 150 mg l−1. In comparison to treatments performed at 20°C, the application of a heated cyprodinil mixture resulted in significantly higher residues in fruit. All treatments with cyprodinil at 20°C similarly reduced green mould after 7 days of storage at 20°C. After 18 days, treatment with cyprodinil at 600 mg l−1 for 30 s was more effective than at 150–300 mg l−1. When dip time was extended to 90 or 180 s, treatment efficacy was positively related to fungicide concentration. Treatments with water at 55°C for 30 s were as effective as cyprodinil at 50–100 mg l−1, but less effective than cyprodinil at 150 mg l−1. After 7 days, treatment with water or cyprodinil at 50–150 mg l−1 and 60°C were equally effective in controlling green mould; while, after 18 days, treatment with cyprodinil at 150 mg l−1 was consistently more effective than at 50–100 mg l−1 or hot water alone.

5.14 – Minimal Processing of Fruit and Vegetables: Influence on Concentration and Activity of Some Naturally Occurring Antioxidants in Orange Derivatives

Nutritional factors are widely proved to be critical for human health. Overwhelming, evidence from epidemiological studies showed that diets rich in fruit and vegetables are associated with a reduced risk of degenerative diseases. This is attributed to the fact that these foods may provide an optimal mix of phytochemicals, such as antioxidants and their precursors. However, it is widely recognised that the health promoting capacity of fruit and vegetables strictly depends on their technological history. Processing is expected to affect content, activity and bio-availability of naturally occurring antioxidants. Although some experimental evidence has recently demonstrated that processing may have many effects, not always resulting in a loss of the health promoting capacity of fruit and vegetables, uncertainty still exists about the effective incidence of the various technological steps. This aspect, which is generally neglected or scarcely considered in present nutritional and epidemiological studies, is of great importance, considering that only a small amount of fruit and vegetables are consumed as fresh, whilst most of them need to be processed for safety, quality and economic reasons. Thus, investigation on the effects of processing on the activity of naturally occurring antioxidants is a key factor in order to find out the best technological conditions for preserving the above cited beneficial properties and to achieve a correct interpretation of data on dietary habits and human health. In the present investigation fresh and pasteurised orange juices, chosen by virtue of their high content in naturally occurring antioxidants and their widespread consumption, were considered. The changes in ascorbic acid concentration and in the overall antioxidant properties during juice preparation and storage, the latter carried out under different temperature conditions, were studied.