Chitosan and hot water treatments reduce postharvest green mould in ‘Murcott’ tangor

Abstract

This study aims to evaluate the efficacy of hot water and chitosan treatments to control green mould caused by Penicillium digitatum in 'Murcott' tangor. P. digitatum conidial germination and mycelial growth were evaluated in assays in vitro to verify whether chitosan (0.5, 1 and 2%) or hot water (45, 50, and 55°C, for 30 s, 1, 2, and 5 min) acts directly on fungus development. In vivo assays consisted of inoculating the fruit with P. digitatum (105 conidia ml−1) 4 hr before the chitosan and hot water treatments. Subsequently, green mould incidence and severity were evaluated in fruits stored at 25°C/80% RH for 4 days. Also, treatments combining chitosan and hot water were investigated for controlling green mould and the effect on postharvest quality of fruit stored at 5°C/90% RH. The results showed that P. digitatum conidia germination and mycelial growth were significantly reduced by the hot water treatments especially at 50°C/5 min and 55°C/2 or 5 min in the first case and 50 and 55°C/5 min in the second. These two treatments, when applied alone, 1 min dipping in 2% chitosan or hot water at 50°C/5 min, significantly reduced green mould development in fruit kept at 25°C/80% RH or refrigerated. However, the hot water dip combined with chitosan did not improve green mould control on ‘Murcott’ tangor at room temperature or under refrigeration. Besides, chitosan and hot water did not impair fruit quality. Thus, chitosan and hot water could be an alternative to synthetic fungicides to control green mould in citrus while also contributing to a decrease in the postharvest losses of ‘Murcott’ tangor.

Effect of Chitosan–Riboflavin Bioconjugate on Green Mold Caused by Penicillium digitatum in Lemon Fruit

“…These results reaffirmed the use of 2% w/v CH-RF as the dose that showed a more extended inhibitory period. This result is consistent with previous reports about the use of chitosan in grapefruits, demonstrating nearly no control of the pathogen with 1% w/v chitosan [15] and no significant differences in the incidence on day 4 of evaluation compared to the control using chitosan even at 3% w/v [18]. Our results showed an increased and significant inhibitory effect on incidence and severity using 2% w/v CH-RF.…”

“…In assays in mandarins, a reduction in incidence and severity was observed seven days after inoculation [16]. Similar results were observed on cold storage [17], while other authors report no reduction in incidence four days after inoculation [18].…”

“…Other reports using a coating of chitosan solution con-ducted with oranges showed no incidence of P. digitatum in cold storage for up to three or four weeks [29]. Also, using 2% w/v chitosan coating on mandarins, and then, storing them for 15 days at 5 • C and 5 days at 25 • C [18] found no reduction in the incidence of green mold but a reduction in decay severity. The differences across studies regarding cultivar susceptibility, inoculum concentration, or strain virulence may account for the inconsistent results.…”

“…Chitosan is a natural biopolymer with proven antifungal effects against various fungi. The control of green mold with chitosan has been previously evaluated in vitro and in different citrus species, such as lemons, oranges, and grapefruit [16][17][18]28,29]. In addition, there are increasing studies using photoactive compounds to inhibit or reduce the growth of several postharvest fungi.…”