Mode of Action of Hot-Water Dip in Reducing Decay of Lemon Fruit

Abstract

A hot-water dip for 2 min at 52-53 degrees C prevented decay for at least one week in lemon fruit inoculated with Penicillium digitatum. The mode of action of hot water in reducing decay was investigated by studying the effects of this treatment on the pathogen and on the resistance mechanisms of the fruit. The hot-water dip had a transient inhibitory effect on the pathogen, arresting its growth for 24-48 h. During this lag period, the combined effects of the pathogen and the hot-water dip induced the build up of resistance in the peel. Lignin production in the inoculated sites began within 24 h after inoculation or wounding. When inoculation was followed by the hot-water dip, lignin accumulation continued for a week. Inoculated lemons that were not dipped in hot water rotted completely within 3 days after inoculation and their lignin content did not rise or even decreased. The scoparone concentration in the inoculated sites of hot dipped fruit started to rise 24 h after treatment and reached a level sufficient to inhibit the pathogen within 2 days after treatment. Parallel to scoparone accumulation, scopoletin was detected in inoculated and heat-treated lemons. Without the pathogen challenge or wounding, heat treatment by itself was not able to induce any of the above-mentioned defensive effects. Our data do not support the involvement of ethanol-extractable aldehydes, associated in the literature with wound gum, or of citral in decay inhibition in hot-water dipped lemons.

Hot water incorporated with salicylic acid dips maintaining physicochemical quality of ‘Holland' papaya fruit stored at room temperature

“…Moreover, heat treatment could induce antioxidant defense responses due to production of bioactive compounds and antioxidant enzymes in fruit (Vincente et al, 2006). Postharvest quality maintenance by hot water treatment has been reported for papaya fruit (Lazan et al, 1989), lemon fruit (Nafussi et al, 2001), banana fruit (Promyou et al, 2008), jujube fruit (Promyou et al, 2012), sweet leaf bush .…”

Controle em pós-colheita de Penicillium digitatum EM laranja-pera com microrganismos e tratamento térmico

“…Similarmente, o tratamento térmico a 52 ºC, 55 ºC e 60 ºC por, respectivamente, 120; 60 e 20 segundos, reduziu o desenvolvimento dos bolores verde e azul em tangerinas Satsuma, armazenadas por 21 dias a 5 ºC e sete dias a 18 ºC (HONG et al, 2007). O tratamento térmico não causou a morte total dos conídios de Penicillium, pois o tratamento desses a 52-53 ºC, por dois minutos, seguidos da inoculação em limões, não preveniu a ocorrência da doença, mas atrasou seu desenvolvimento (NAFUSSI et al, 2001). Porat et al (2000) verificaram que os conídios de P. digitatum têm a germinação inibida quando submetidos às temperaturas de 59 e 62 ºC, por 15 a 20 segundos, enquanto a 56 ºC, por 20 segundos, atrasa a germinação.…”

“…Segundo Nafussi et al (2001), frutos de limão, feridos, inoculados e tratados com água a 53 ºC apresentaram aumento do depósito de lignina no sítio de inoculação. Adicionalmente, frutos tratados em banho térmico, dois dias após a inoculação com P. digitatum, apresentaram aumento de escoparina e escopoletina.…”

“…O tratamento térmico, antes do armazenamento, é uma alternativa aos fungicidas, tanto inibindo o crescimento do patógeno, como ativando os mecanismos de resistência do fruto (NAFUSSI et al, 2001). Em frutos de Citrus reticulata x Citrus sinensis, a combinação de diferentes temperaturas e tempos de exposição (56; 59; 62 e 65 ºC por 1; 2 e 3 minutos) reduziu a incidência do bolor verde, apresentando ação fungistática, pois com o tempo de armazenamento ocorreu aumento da incidência da doença (KYRIACOU, 2011).…”

Biosíntesis de Carotenoides durante la Conservación Postcosecha de Frutos Citricos

“…Los tratamientos postcosecha de choque térmico han demostrado una alta eficacia en la inducción de tolerancia a las bajas temperaturas de conservación y en el control de podredumbres en frutos de diversas especies y variedades de cítricos (Ben-Yehoshua et al, 1995;González-Aguilar et al, 1997;Lurie, 1998;Nafussi et al, 2001;Schirra et al, 2004;Erkan et al, 2005b;Nunes et al, 2007).…”