Extension of green bell pepper shelf life using oilseed-derived lipid films from soapstock.

Authors: Beaulieu, John; Mims, Amelia; Kuk, Myong; PARK, H.S. - University Of New Orleans

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2009
Publication Date: 6/17/2009
Citation: Beaulieu, J.C., Mims, A.G., Kuk, M.S., Park, H. 2009. Extension of green bell pepper shelf life using oilseed-derived lipid films from soapstock. Industrial Crops and Products. 10:1016.

Interpretive Summary: Edible films and waxes have been used for decades on fresh produce to create a semipermeable membrane on the surface to suppress respiration, control moisture loss, and more recently, to provide a delivery mechanism for additional functional components. Edible films composed of straight-chained fatty acids have been used as a shelf life extender applied to cereal products. After vegetable oil production from oil-bearing seed materials, an underutilized byproduct called soapstock is produced. In the past decades, soapstock has been recovered as raw materials for producing low grade industrial soaps, and it may also be used in animal feeds. Because of low economical return, most soapstock is rarely recovered today, but added back to animal feed without much economical compensation. Alternative byproducts such as lipid film constituents or biodiesel production have been explored with soapstocks, and, therefore, may be warranted. The Southern Regional Research Center (SRRC) has previously demonstrated that a thin biodegradable film can be produced from soapstock, an underused byproduct from the vegetable oil industry, after physical and chemical treatments. Subsequently, to examine the potential use of an oilseed derived lipid film for extension of shelf life, different types of the oilseed-derived soapstocks were utilized to produce lipid films with different hydration ratios, and containing 0, 5, and 10 % of paraffin wax for application on ‘Camelot’ bell peppers. Control bell peppers stored under ambient conditions lost almost 25% weight per unit surface area (SA) in 78 h. Peppers receiving cottonseed film hydrated at 1:4 lost only roughly 5% moisture per unit SA after 78 h, and minimized weight loss by up to 79% compared to the control. Safflower-derived soapstock film resulted in the least effective water retention of the films and ratios tested, with roughly 21 to 25% reduction in weight loss per SA compared to controls. Addition of wax to the cottonseed-derived films decreased slightly the water vapor permeability, similar to previous reports in the literature. Statistics supported the conclusion that the oilseed-derived lipid films significantly reduced moisture loss across the produce epidermis.

Technical Abstract: Edible films have been used for decades on fresh produce to create a semipermeable membrane on the surface to suppress respiration, control moisture loss, and more recently to provide a delivery mechanism for inclusion of functional components. Scientists at the Southern Regional Research Center (SRRC) have previously demonstrated that a thin biodegradable film can be produced from soapstock, an underused byproduct from the vegetable oil industry. After physical and chemical treatments, a thin film was produced from various soapstocks (cottonseed and safflower). Different hydration ratios were tested since the initial soapstock solutions were rather viscous. To examine the potential use of an oilseed derived lipid film for extension of shelf life, different types of the oilseed-derived soapstocks were utilized to produce lipid films with different hydration ratios, and containing 0, 5, and 10 % of paraffin wax for application on 'Camelot' bell peppers. When stored under ambient conditions, control bell peppers lost almost 25% weight per unit surface area (SA) in 78 h. Cottonseed film hydrated at 1:4 lost only roughly 5% moisture per unit SA after 78 h and minimized weight loss by up to 79% compared to the control. However, since a 1:4 hydration ratio remained rather viscous, 1:8 was preferred and these cottonseed films reduced weight loss per unit SA by up to 48% during storage. Safflower-derived soapstock film resulted in the least effective water retention of the films and ratios tested, with roughly 21 to 25% reduction in weight loss per SA compared to controls. Safflower-derived soapstock was higher in unsaturated fatty acids, which are less efficient to control moisture migration because they are more polar than saturated lipid materials, as contained in cottonseed-derived materials. Addition of wax to the cottonseed-derived films decreased slightly water loss, similar to previous reports in the literature. An ANOVA supported the conclusion that the oilseed-derived lipid films significantly reduced moisture loss across the produce epidermis. To avoid potential allergenicity concerns in cottonseed soapstock, additional clean up steps and tests with commonly used edible coating additives would be required in other soapstocks before attaining food grade status.