Effect of antioxidant and optimal antimicrobial mixtures of carvacrol, grape seed extract and chitosan on different spoilage microorganisms and their application as coatings on different food matrices

Abstract

There is growing interest in the use of natural agents with antimicrobial (AM) and antioxidant (AOX) properties. Optimization of the AM capacity for mixtures containing carvacrol, grape seed extract (GSE) and chitosan, against gram-negative (Pseudomonas aeruginosa), gram-positive bacteria (Staphylococcus aureus, Listeria innocua and Enterococcus faecalis) and yeast (Saccharomyces cerevisiae) at 10 6 cfu mL −1 was studied. To observe the synergistic or antagonistic effect and find optimal combinations between the three agents, a simplex centroid mixture design was run for each microorganism, combining carvacrol (0-300 ppm, X1)X, GSE (0-2000 ppm, X2) and chitosan (0-2% w/v, X3). Results of the response surface analysis showed several synergistic effects for all microorganisms. Combinations of 60 ppm-400 ppm-1.2% w/v (carvacrol-GSE-chitosan; optimal AM combination 1, OAMC-1); 9.6 ppm-684 ppm-1.25% w/v (OAMC-2); 90 ppm-160 ppm-1.24% w/v (OAMC-3) were found to be the optimal mixtures for all microorganisms. Radical scavenging activity (RSA) of the same agents was then compared with a standard AOX (butylated hydroxytoluene; BHT) at different concentrations (25, 50 and 100 ppm; as well as the optimal AM concentrations) by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. RSA increased in the following order: chitosan< carvacrol< BHT< GSE and for the OAMC: OAMC-2< OAMC-1< OAMC-3. The best RSA (OAMC-3) was applied as a coating in two different food matrices (strawberries and salmon). For strawberries, P. aeruginosa was more sensitive to the action of OAMC-3 than S. cerevisiae. For salmon, S. aureus was more resistant to the action of OAMC-3 than E. faecalis and L. innocua.

Comparison of Two pH Responsive Color Changing Bio‐Based Films Containing Wasted Fruit Pomace as a Source of Colorants

“…CS films could have greater flexibility due to the presence of β‐(1‐4) D glucosamine linkages that were not found in CMC (Shingel, ). The E values for CS were similar to 28% given by Rubilar (), but in both studies these values were higher than 17% found by Vargas, Albors, Chiralt and González‐Martínez (). Differences are attributed to differences in CS powder source with variations in deacetylation degree, natural impurities, type, and content of plasticizer (Rubilar, ).…”

“…The E values for CS were similar to 28% given by Rubilar (), but in both studies these values were higher than 17% found by Vargas, Albors, Chiralt and González‐Martínez (). Differences are attributed to differences in CS powder source with variations in deacetylation degree, natural impurities, type, and content of plasticizer (Rubilar, ). Control CMC films had similar E as previously reported (Tong, Xiao, & Lim, ).…”

Mathematical modeling of gallic acid release from chitosan films with grape seed extract and carvacrol

“…Finally, after the chitosan solution was homogenized with glycerol and Tween-80, the AM agents were added and mixed using an Ultra-Turrax (Ika-Werke, model T25, Germany) at 9500 rpm for 5 min, according to the desired final concentration (Table 1) in each film. Based on the previous studies [8,16], three optimal concentrations were prepared using a simple centroid mixture design between carvacrol, GSE and chitosan, as shown in Table 1. After cooling to room temperature, the solutions were degassed at 6 68 kPa (Edwards, BS 2208, UK) for 5 min and then 200 mL (for each film) were cast onto 32 cm round glass plates, and dried at 25 ºC for 48 h. Each film was then stored in desiccators at 25 ºC and 57% relative humidity, using a NaBr (02119, Sigma Aldrich, Portugal) saturated solution until testing.…”

“…Chitosan, a natural polymer obtained by deacetylation of chitin, has been widely used to produce biodegradable films [8,15,16] with several recent reviews on chitosan-based films available [17][18][19]. The AM and/or AOX properties of such films may be improved by adding different natural compounds.…”

“…Different studies reported the use of plant essential oils as natural AM agents [20,21]. Among these, carvacrol is a phenolic compound with demonstrated AM activity against bacteria, fungi and yeast [1,16]. It is the main component (50-86%) found in essential oils of spices such as oregano (Origanum sp.)…”