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Date of Award

9-2013

Document Type

Campus Access

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Food Science

First Advisor

Julie M. Goddard

Second Advisor

Eric A. Decker

Third Advisor

Bryan Coughlin

Subject Categories

Chemistry | Food Science | Polymer Chemistry

Abstract

Lipid oxidation is a significant issue in the food industry, which can cause severe food quality deteriorations and nutrition losses. Transition metals, especially iron, are a main factor to accelerate lipid oxidative reactions in food systems. Non-migratory active packaging techniques provide an alternative strategy to food preservations without the need for food additives. The objective of this work was to develop non-migratory metal chelating active packaging films to control the iron-promoted lipid oxidation in food products. Both "grafting to" and "grafting from" techniques were used to introduce metal chelating polymer poly(acrylic acid) (PAA) onto inert packaging film surfaces. Compared to the "grafting to" approach, graft polymerization of PAA yielded a higher available carboxylic acid density on the packaging film surface, with a stronger chelating activity toward both Fe2+ and Fe 3+ . Compared to the native polypropylene (PP) film, the PP- g -PAA film prepared by the "grafting from" approach significantly delayed the lipid oxidation in an oil-in-water emulsion system by a factor of 4~5 times at pH 7.0. PP-g -PAA films equally inhibited lipid oxidation throughout the range of surface area-to-product volume (SA/V) ratios tested (2 to 8 cm2 /mL), and were most capable of preventing lipid oxidation in foods at pH values of 5.0 and higher. A siderophore-mimetic poly(hydroxamic acid) (PHA) was grafted from PP film surface to mimic the chelating property of siderophores, naturally occurring small molecules with high specificity and affinity toward Fe 3+ . The PHA showed a broad active pH range, which retained 50% ability to chelate iron at pH 3.0 compared to pH 5.0, almost double the retention of low-pH chelating ability of PAA. In an accelerated lipid oxidation study at pH 3.0, PP-g -PHA films performed even better than EDTA in preventing the formation of volatile oxidation products in emulsion systems. The particle size and zeta potential of emulsions indicated that both PP-g -PAA and PP- g -PHA films would unlikely affect the physical and chemical stability of the emulsion system. The results of this work suggest that the application of non-migratory active packaging films represents a promising approach to reduce additive use while maintaining food quality.

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