Introduction: Meat and meat products undergo chemical and microbial spoilage during production, transportation, storage and consumption. Antimicrobial edible coatings containing natural herbal extracts and essential oil possess various benefits and are currently used to design novel active biodegradable packaging. Natural polysaccharides are considered as potentially good candidates to fabricate edible coatings and provide a shelf life extender. There are no researches in the literature concerning the potential effect of Carum copticum essential oil (CCEO) enriched Scutellaria lateriflora seed mucilage (SLSM) based edible coatings on the quality and shelf life of lamb during refrigeration storage. The objective of this study was therefore to investigate the inhibitory effect of CCEO loaded SLSM edible coating towards lipid oxidation and microbial spoilage of lamb during cold storage conditions.
Materials and methods: In this study, SLSM was extracted from whole seeds using hot-water extraction. Edible coating was prepared by dissolving 2 g of the extracted SLSM and 0.1 g of Tween 80 in 100 mL of sterilized distilled water. The mixture was stirred and heated for 2 h. Afterwards, CCEO was added to the SLSM solution at 0, 1, 1.5, and 2%, and the obtained solution was used as an antimicrobial coating for extending the shelf-life of lamb slices. The control and the coated lamb samples were analyzed periodically for microbiological (total viable count, psychrotrophic count, Escherichia coli, Staphylococcus aureus and fungi), chemical (peroxide value and pH), and sensory characteristics (color, odor and overall acceptability).
Results and discussion: SLSM extended the microbial shelf life of lamb by 3 days, whereas SLSM + 1% CCEO, SLSM + 1.5% CCEO and SLSM + 2% CCEO resulted in a significant shelf life extension of the lamb by 6, 6, and 6 days, respectively as compared to the control samples. The results demonstrate that the EO-rich edible coating functions as an oxygen barrier and, in turn, limits the growth of most important and aerobic psychrotrophic bacteria, i.e. Pseudomonas species, which are mainly responsible for the fresh lamb spoilage under aerobic conditions. The results showed that the pH of lamb coated with SLSM and samples containing CCEO was lower than the control. The results showed that the peroxide value in the control sample increased from 0.4 to 9.7 meq oxygen/kg during 9 days of refrigerated storage. Based on the finding of this study, the use of CCEO-loaded coating manifestly lowered the meat lipid oxidation. The resultant edible coating manifestly improved the shelf life of lamb through suppressing microbial spoilage and inhibiting lipid oxidation. The coating containing 2% CCEO conferred good quality characteristics to the lamb and expanded its refrigeration shelf life.