Development and application of new polymeric materials based on chitosan, gelatin, and pomegranate (Punica Granatum L.) peel extract for coating and improving the post-harvest quality of strawberries (Fragaria × ananassa Duch.)

Author(s)

Mirella Romanelli Vicente Bertolo

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2024-01-12

Examining board members

Stanislau Bogusz Junior; Renato Lajarim Carneiro; Daniel Souza Corrêa; Ana Elizabeth Cavalcante Fai; Bianca Chieregato Maniglia

• Advisor: Stanislau Bogusz Junior

Abstract

Post-harvest losses are defined as measurable changes or reductions in food quality and/or quantity, after being harvested, that make them unsuitable for human consumption. In practice, they result from diseases caused by fungi and bacteria, physiological disorders, and physical damage to fruits. New low-cost conservation technologies have been developed to reduce post-harvest food losses, like the use of natural polymeric coatings. Thus, the main aim of this thesis was the development of coatings based on chitosan, gelatin, and pomegranate peel extract to maintain the physical-chemical, microbiological, and sensorial quality of strawberries. The coating formulation was optimized with the aid of chemometric tools, and the coating containing 0.8% chitosan, 0.2% gelatin and 1 mg g-1 pomegranate peel extract was applied to strawberries in their post-harvest period. The physical-chemical and microbiological properties of coated fruits were compared to those of control fruits (without coating). The coated fruits showed lower percentages of weight loss and fungal contamination throughout storage and maintained their color and firmness. The coating also slowed the declines in the respiratory rates of the fruits and in their profile of bioactive and volatile compounds. A sensory difference from control test was conducted with trained tasters, who were unable to differentiate uncoated fruits from those covered with the developed coatings. The cost of the coating was also estimated, being around R$0.13/fruit. Furthermore, new possibilities for studying the topic were presented: the application of the coating was combined with the application of light in photodynamic therapy, and the effects of this combination on the properties of strawberries were evaluated. In addition to not altering the quality of the fruits, the combination extended the shelf life of the strawberries and improved their microbial safety. In another aspect of study, the so-called natural deep eutectic solvents (NADES) were used as alternative and green means of extracting phenolic compounds from pomegranate peel, as well as two other agro-industrial residues of economic importance for the state of California (where this part of the study was conducted), almond hulls and elderberry pomace. NADES containing choline chloride and lactic acid was chosen as the most suitable for the optimization study of ultrasound-assisted extractions for the three materials. This solvent showed better results in relation to the concentration and composition of phenolics in the extracts, when compared to an ethanolic solution (60%, v/v). Such results open new possibilities for the use of NADES as phenolic carriers and as plasticizing agents in chitosan and gelatin-based coatings. (AU)

• FAPESP's process: 19/18748-8 - Chemical composition of strawberries coated with biofilm-based on pomegranate peel extract, chitosan, and gelatin
• Grantee: Mirella Romanelli Vicente Bertolo
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)