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 Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Veronica C. Sabularse

Abstract

Chitosan nanoparticles (NCh) wcrc prepared from a 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.IN CII3C0011 solution, 0.6% soluble in water and insoluble in 0.1N NaOH solution. Its degree of deacetylation (DD) was 57.71 + 1.40%. The presence of amide groups was confirmed by the presence of C-N and C-0 amide bands in its infrared spectrum. N-H and C-N bands 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 (Ch8ONCh+add) appeared compact and thin compared to films with I% chitosan only (Ch+add) and that containing 40°A nanochitosan (Ch4ONCh+add). Thc 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 7' and 10th day of storage, respectively. The Ch+add coated fruits reached their limit of marketability on day 14 of storage while the Ch4ONCh+add and Ch8ONCh+add coated fruits on day 26. Physical and chemical changes wcrc monitored during storage. Both Ch4ONCh+add and Ch8ONCh+add coatings wcrc effective in retarding peel color change, minimizing disease incidence and shriveling, and maintaining peel and pulp firmness. Thc Ch4ONCh+add formulation was more effective in minimizing weight loss while the Ch8ONCh+add was more effective in maintaining fruit pulp pH and slowing down conversion of starch to glucose. No significant effect was observed for titratablc 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 till in voids in the coating structure, hence, maintaining low respiration and transpiration rates and reducing ethylene production ss Inch led to a delay in fruit ripening.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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