Elsevier

Food Chemistry

Volume 145, 15 February 2014, Pages 454-463
Food Chemistry

Effect of CO2 deastringency treatment on flesh disorders induced by mechanical damage in persimmon. Biochemical and microstructural studies

https://doi.org/10.1016/j.foodchem.2013.08.054Get rights and content

Highlights

  • Persimmon flesh disorders were biochemical and microstructural studied.

  • Persimmon flesh browning are induced by the mechanical impacts to which fruit are exposed during packing.

  • Different flesh disorders are manifested depending on the level of astringency.

  • CO2 deastringency treatment as well as mechanical damage induce oxidative stress.

  • Flesh disorders of persimmon are associated to a tannins oxidation process.

Abstract

Manifestation of flesh browning while commercialising ‘Rojo Brillante’ persimmon is one of the main causes of postharvest loss. It is known that mechanical damage is a decisive factor for browning development and that astringent fruit is less sensitive to this disorder than fruit submitted to a CO2 deastringency treatment under standard conditions (24 h, 95% CO2, 20 °C). However, there is no information available about the mechanism behind this alteration. In the present study, we evaluated the effect of treatment with high CO2 concentrations applied for 0–40 h on the incidence of mechanical impact-induced flesh disorders using biochemical, chromatographic and microstructural techniques. Our results show that the longer the CO2 exposure, the higher the incidence and the greater the severity browning. A deastringency treatment with CO2 results in O2- accumulation in fruit, which is greater the longer treatment is. However, mechanical damage triggers the browning manifestation, resulting in the accumulation of both O2- and H2O2. In this oxidative stress state, which must be greater as higher the level of O2- previously accumulated in the deastringency treatment, insoluble tannins initially uncolour, undergo an oxidation process and turn red-brown, observed as flesh browning. Moreover, we identified a new disorder, “pinkish-bruising”, which is manifested in astringent fruit. The mechanism of this alteration, also associated with mechanical damage, seems similar to that of browning, but the oxidation process would affect soluble tannins.

Introduction

Currently, the incidence of flesh browning is one of the main causes of postharvest loss of the ‘Rojo Brillante’ persimmon, which is the persimmon cultivar mainly cultivated in the Mediterranean region. The cause of this disorder, which appears during the commercialisation period, remains unknown. It was recently reported that the mechanically damage that fruit are submitted to during packing operations may be a decisive factor of browning manifestation (Besada, Arnal, Salvador, & Martínez-Jávega, 2010a).

As this cultivar belongs to the group of persimmon cultivars that are astringent at harvest, fruit are routinely submitted to a postharvest deastringency treatment based on the exposure of fruit to a high CO2 concentration in order to remove astringency prior to commercialisation (Salvador et al., 2007). Persimmon astringency is due to the high concentration of soluble tannins present in fruit flesh. The effectiveness of CO2 treatment to remove astringency is based on the insolubilisation of tannins by the acetaldehyde generated during anaerobic respiration intermediating, which is triggered when fruit is exposed to a high CO2 atmosphere (Matsuo and Ito, 1982, Matsuo et al., 1991). Application of treatment at 95–100% CO2 for 24 h at 20 °C has been established as optimal conditions to ensure the removal of astringency in ‘Rojo Brillante’ persimmon (Besada et al., 2010b, Salvador et al., 2007). Our former studies showed that fruit which have been previously submitted to the deastringency treatment (non astringent fruit) are susceptible to manifesting mechanical impact-induced browning, while astringent fruit are less susceptible to displaying this alteration after packing operations. Thus tannins have been suggested to be implied in the browning process (Besada, Salvador, Vázquez-Gutiérrez, Hernando, & Pérez-Munuera, 2012).

One of the main causes of browning in fruit and vegetables is the oxidation and polymerisation of phenolic compounds due to the activation of enzymes such as phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD). In persimmon fruit, the cause of external bruising has been poorly investigated. Lee, Kim, Kim, and Park (2005) reported no significant changes in lipid peroxidation, as expressed by malondialdehyde production, among bruised and unbruised persimmon cv. Fuyu; these authors also reported that although increased polyphenol oxidase activity appeared to be associated with the visual deterioration of bruised fruits, it could not be the only factor to influence the bruising manifestation. Similarly, our previous studies showed no significant changes in PPO and PAL activity between browned and sound flesh of ‘Rojo Brillante’ persimmon. However, POD enzyme activity has been associated with mechanical damage and browning manifestation (Khademi, Salvador, Zamani, & Besada, 2012).

Furthermore, reactive oxygen species (ROS) are produced as a normal plant cellular metabolism product. Various environmental stresses lead to excessive ROS production; such disturbances in the equilibrium between the production and scavenging of ROS bring about a sudden increase in intracellular ROS levels, which can severely damage cell structures (Gill and Tuteja, 2010, Sharma et al., 2012). Anaerobic atmospheres have been described as one of the environmental stresses that induces an oxidative burst in plants (Blokhina et al., 2001, Blokhina et al., 2003). Moreover, changes in ROS levels have been related to fruit deterioration in association with mechanical damage of fruit like apricots and pears (De Martino et al., 2006, Li et al., 2010). There is no information about the effect of CO2-deastringency treatment on the redox state of persimmon, and no studies have addressed the involvement of ROS in persimmon browning in association with mechanical damage.

This study aimed to investigate the effect of the deastringency treatment with high CO2 concentrations and the level and form (soluble/insoluble) of tannins in the mechanical-induced browning of persimmon fruit. Elucidate the implication of ROS in browning manifestation was also an objective of this research. Microstructural techniques were used to describe browning alterations.

Section snippets

Vegetal material and experimental design

Persimmon (Diospyros kaki Thunb. cv. Rojo Brillante) fruit were harvested in l’Alcúdia (E Spain) at commercial maturity stage. The harvesting date was November 8, when fruit presented an external colour index = 11 and firmness value of 44.9 N. After harvest, fruit were taken to the Instituto Valenciano de Investigaciones Agrarias (IVIA), where they were carefully selected for uniformity of size and colour, and for lack of defects.

Thirty-six lots of 20 fruits were formed and one lot of fruit was

Study of the physiological parameters related to astringency

Soluble tannin and acetaldehyde content are the main parameters relating to the astringency removal process when submitting fruit to high CO2 concentrations. Therefore, we determined them both in the fruit submitted to different CO2 treatments (0, 6, 12, 18, 24, 32 and 40 h). Besides, fruit astringency was also evaluated by a sensory panel.

The fruit not exposed to CO2 (0 h treatment) showed a soluble tannins content of 0.6% fw (Supplementary Fig. S1A), which are habitual values at harvest in the

Discussion

This work initially focused on studying the flesh browning disorder of the ‘Rojo Brillante’ persimmon. Nevertheless while this research line was underway, another flesh disorder was identified, which we named “pinkish-bruising”. Here, we attempt to collect data from the physiological, microstructural and chromatographic studies obtained in this paper, together with previous results from our laboratory, to help gain a better understanding of the flesh browning process in persimmon.

Acknowledgments

This study has been supported by the Spanish ‘Ministerio de Economía y Competitividad (Project INIA-RTA 2010-00086-00-00) and FEDER Program from the EU. We thank to ‘D.O. Kaki Ribera del Xúquer’ for his support for these studies. We thank Ph.D. Takashi Tanaka (Nagasaki University) for his support during the chromatographic analysis. Ph.D. Cristina Besada is contracted by the ‘Regional Ministry of Education of the Valencian Community’.

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