Location: Healthy Processed Foods ResearchTitle: Physical, mechanical and transport properties of emulsified films based on alginate with soybean oil: Effects of soybean oil concentration, number of passes and degree of surface crosslinking
|GUTIERREZ-JARA, CAMILO - University Of Bío-Bío|
|VILLALOBOS-CARVAJAL, RICARDO - University Of Bío-Bío|
Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2020
Publication Date: 6/30/2020
Citation: Gutierrez-Jara, C., Bilbao-Sainz, C., McHugh, T.H., Chiou, B., Williams, T.G., Villalobos-Carvajal, R. 2020. Physical, mechanical and transport properties of emulsified films based on alginate with soybean oil: Effects of soybean oil concentration, number of passes and degree of surface crosslinking. Food Hydrocolloids. 109. Article 106133. https://doi.org/10.1016/j.foodhyd.2020.106133.
Interpretive Summary: Great advances have been achieved in minimally processed food maintenance using edible coatings. However, their water vapor permeability and mechanical properties are generally worse than synthetic films. Bio-based polymers can be combined with hydrophobic compounds to produce composite films with better functionality. Hydrophobic compounds can be added as emulsions. In this work we used microfluidization to add soybean oil in water emulsions to alginate-based films. We evaluated the effect of different soybean oil concentrations (0.5%, 1.0% and 1.5% v/v), globule size using different number of passes in the microfluidizer (2, 4 and 6 times) and level of surface crosslinking with calcium chloride (0 %, 1.5% and 3 %) on the physical, mechanical and transport properties of nanoemulsified sodium alginate films. We found out that all formulations containing oil had lower water vapor permeability values compared to pure alginate film, although there were no clear effects for oil and calcium chloride concentrations. The porosity of the films was mainly affected by the soybean oil content with higher oil content leading to lower porosity. From results in this study, 0.5% oil formulation obtained after 6 passes through the microfluidizer and treated with 3% calcium chloride is best suited for coating cherries. This film contained well dispersed oil drops and low moisture sorption due to surface crosslinking. In addition, the 0.5% oil film allowed permeability of oxygen and would not interfere with respiration in cherries, unlike films containing higher concentrations of oil.
Technical Abstract: Edible films and coatings have been applied on fruits to improve their quality during growth and development as well as during post-harvest storage. However, there have been few studies on using coatings to reduce fruit waste. Response surface methodology was used to determine the effects of oil concentration, number of passes and calcium chloride concentration on physical, mechanical and transport properties of oil-alginate composite films. Alginate based films were developed using alginate (1.0% w/v), soybean oil (0.5%, 1.0% and 1.5% v/v) and Tween 80® (1% v/v). Coarse emulsions were passed 2, 4 and 6 times through a microfluidizer at 200MPa. Calcium chloride solutions (0 %, 1.5% and 3 %) were then applied on the cast films to crosslink them. The oil particle sizes ranged from 360-445 nm, regardless of the nanoemulsion composition and number of passes. The lowest water permeability value (1.8857E-10 g/msPa) was obtained with 1.5% oil concentration, 6 passes and no crosslinking. The porosity of the films at low oil concentration increased in value with an increase in crosslinking level. In comparison, the porosity of the films at high oil concentration decreased in value with an increase in crosslinking level. Emulsified films showed reduced strength and increased elongation with an increase in oil concentration. Films treated with calcium chloride showed lower strength and elongation values and an increase in brittleness. In conclusion, oil-alginate composite films could be used as coatings to reduce moisture transfer during fruit development and storage.