title: SeaCoat - Marine based edible coatings for minimally processed fruit
Creators: name: Augusto, Ana
Publisher: name: University of Reading
Year: 2022

description: 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.