Preparation and utilization of chitosan nanoparticles in chitosan-based coatings and its effect on the postharvest life of papaya (Carica papaya L.) fruits

Date

4-2011

Degree

Bachelor of Science in Agricultural Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Veronica C. Sabularse

Committee Member

Hidelisa P. Hernandez, Edralina P. Serrano

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Abstract

Chitosan nanoparticles (NCh) were prepared from a prepared low molecular weight chitosan (LWCh) and from chitosan with a molecular weight of 223KD. The nanochitosan prepared from a 223KD chitosan had a lower average particle size of 112 nm compared to 434 nm for the LWCh. The small sized nanochitosan was then used in the formulation of chitosan-nanochitosan (Ch-NCh) films and coatings. The chitosan used in the polymer matrix was 50% soluble in 0.1N CH3COOH solution, 0.6% soluble in water and insoluble in 0.1N NaOH solution. Its degree of deacetylation (DD) was 57.71 + 1.40%. Its low DD was confirmed by the presence of C-N and C=O amide stretch in its infrared spectrum. N-H and C-N stretch confirmed the presence of amine in the chitosan molecule. Coating formulations using chitosan as base into which NCh were incorporated were prepared. The film containing 80% nanochitosan (Ch80NCh+add) appeared compact and thin compared to films with 1% chitosan only (Ch+add) and that containing 40% nanochitosan (Ch40NCh+add). The ability of these films to extend the shelf-life of “Sinta” papaya was evaluated. Papaya fruits were stored at 14.6 °C and 79% RH. Control (uncoated) and blank (additives only) fruits reached their limit of marketability on the 7th and 10th day of storage, respectively. The Ch+add coated fruits reached their limit of marketability on day 14 of storage while the Ch40NCh+add and Ch80NCh+add coated fruits on day 26. Physical and chemical changes were monitored during storage. Both Ch40NCh+add and Ch80NCh+add coatings were effective in retarding peel color change, minimizing disease incidence and shriveling, and maintaining peel and pulp firmness. The Ch40NCh+add formulation was more effective in minimizing weight loss while the Ch80NCh+add was more effective in maintaining fruit pulp pH and slowing down conversion of starch to glucose. No significant effect was observed for titratable acidity of the coated fruits. Results indicate that incorporation of NCh into coating formulations with chitosan as base could retard fruit ripening. Retardation of fruit ripening using these coatings may be due to the ability of the NCh to fill in voids in the coating structure, thereby, increasing the interaction of particles with the chitosan matrix resulting in a more compact film coating; hence, maintaining low respiration and transpiration rates and reducing ethylene production which led to a delay in fruit ripening.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2011 A13 A45

Document Type

Thesis

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