Abstract/Summary

Fresh-cut fruits and vegetables are in increasing demand, as these products comply with key consumer trends combining health promotion and convenience. Shelf-life of fresh-cut fruits as apples and pears is limited by the development of superficial browning, which causes product rejection by consumers. Fresh-cut fruits requirements limit the array of suitable conservation technologies, with edible coatings application as one of the most used and successful barriers to product degradation. Most of the commercially available solutions include synthetic substances that contribute to a shelf-life of up to 8 days. Options that simultaneously extend shelf-life and comply with consumer demand for natural-based additives will strengthen the resilience of fruits and vegetables value chain. The present thesis aims to evaluate the potential of Codium tomentosum extract as an edible coating for fresh-cut apple and pear, extending fresh-cut fruit shelf-life through superficial browning regulation. For this purpose, C. tomentosum extract-based coating solution was applied as an anti-browning treatment to fresh-cut ‘Rocha’ pear and ‘Fuji’ apple produced under industrial conditions. During the storage period of 15 days at 4 °C, fresh-cut pears coated with the seaweed extract showed lower colour changes and browning index than the control and samples treated with a commercial solution. Fresh-cut apples, stored with modified atmosphere, and coated with the seaweed extract had identical browning index and colour change values to those samples coated with an ascorbate-based commercial additive, possibly because of lower oxidative enzyme activities observed in extract treated samples. For an understanding of the mechanism underlying anti-browning functionality of the extract, gene expression analysis was performed. It was observed that in fresh-cut apple coated with the seaweed extract, peroxidase (mdPOD) and phenylalanine ammonia-lyase (mdPAL) genes expression was particularly affected one hour after the coating application, followed by a reduction in polyphenol oxidase (mdPPO) expression. These results suggest that the aforementioned genes are activated at a later stage, thus contributing to decreased enzymatic activity, and consequently, to a lower browning in treated samples. The effects of time, temperature and pH on the extraction of C. tomentosum, and their influence on the extract functionality, were evaluated. A Response Surface Methodology was applied, and it was observed that higher yields of extraction are obtained with longer extraction periods and neutral to alkaline pH. In terms of the functionality of the extracts, browning compounds absorbance and peroxidase activity were mainly influenced by changes in temperature, especially above room temperature. The present thesis sets baseline key findings to support the use of seaweed extracts as edible coatings in the fresh-cut industry, validates C. tomentosum extract functionality as an anti-browning treatment for fresh-cut fruits and establishes the basis for a thorough understanding of its mechanism of action at a gene expression level.