مجله پژوهشهای علوم و صنایع غذایی ایران (Dec 2023)
Effect of Edible Coatings of Alginate and Oliveria decumbens Essential Oil on Physicochemical, Microbial and Sensory Properties of Grated Carrots During Shelf Life
Abstract
IntroductionToday, carrots are widely used in freshly cut products, including ready to eat salads, however, its shelf life is reduced due to the damage caused on the texture of the product which accelerate the reduction of nutritional value as well as the growth of microorganisms, (Azizian et al., 2020). To increase the shelf life of freshly cut products, it is recommended to use coatings on the surface of these products. Alginate is a hydrophilic biopolymer and having unique colloidal characteristics, it demonstrates a suitable coating function. Olivas et al. (2008) showed that by coating fresh apple slices with alginate and antimicrobial agents increased the shelf life of apple and decreased weight loss. Among the native plants of Iran, we can mention the Oliveria plant, which belongs to the Amblifra family. The aerial parts of this plant have a significant amount of essential oils (EOs). Researches by Amin et al. (2005) on the antimicrobial properties of Oliveria essential oils have shown a broad-spectrum antimicrobial activity against all studied organisms, and this effect is comparable to that of commercial antibiotics. Packaging with modified atmosphere is one of the best ways to increase the shelf life of fruits and vegetables. The purpose of this study was to investigate the effect of alginate and Oliveria essential oils on the physicochemical and microbial characteristics of grated carrots in polypropylene packages with modified atmosphere during storage. MethodsEssential oil of Oliveria plant was extracted, dehydrated by sodium sulfate and placed in sealed glass container and stored at 4˚C until using. Carrots prepared from Wilmoren cultivar. An industrial crusher crushed the carrots, and samples were coated by treatment solutions. Two treatments of coating were prepared, one as control with 0% and the other one with 1.5% alginate with stirring and moderate heat (50-60°C) (Lu et al., 2009). Then the Oliveria EO was added to the alginate solution at the specified concentration. The resulting solution was deaerated at 25˚C.T1: control sample (without coating)T2: 1.5% alginateT3: 150 ppm Olivieria EOT4: 250 ppm Olivieria EOT5: 1.5% alginate and 150 ppm of Olivieria EOT6: 1.5% alginate and 250 ppm of Olivieria EOAfter weighing (250 g), the grated carrots (control and coated) were placed in 10 g polypropylene packages of suitable food grade in dimensions of 50 × 190 × 144 cm and the package was injected with 5% O2, 5% CO2 and 90% N2. The packages were then stored in the refrigerator for 12 days at 4±1˚C. All experiments were performed on days 1, 3, 6, 9, and 12. Evaluation of Chemical, Microbial and Sensory CharacteristicsA pH meter used for pH determination (Rad et al., 2020). The acidity measured based on Rocha et al. (2007) method.The weight was reported using pre and post-storage weight. The carotenoid concentration calculated by Rocha et al. (2007) method. Total soluble solids determined by refractometer (Rad et al., 2020). Ascorbic acid content measured by Falahi et al. (2013) method. The L*, a*, b* and WI (white index) indicators of grated carrots evaluated by Hunter lab system. A 5-point hedonic test was used to assess sensory attributes(Ajnevardi et al., 2002). The internal gas concentration evaluated by Ullsten & Hedenqvist (2003) method. Total count microorganisms, mold, and yeast were counted according to the method of Azizian et al. (2020). Data AnalysisThis study was conducted in a completely randomized design with factorial form to investigate the effect of independent variables of type of alginate coating (2 levels), essential oil (3 levels) and time (5 levels) on the physicochemical properties of grated carrots (3 replications) and total counting, mold and yeast (2 replications). Mean comparison was performed using LSD test at 5% probability level and SPSS software was used to statistically analyze data. ResultThe results showed that the level of acidity, carotenoid and acid ascorbic, the amount of L* and sensory (color, quality, flavor, odor) scores reduced during time. By contrast the level of pH, weight loss, the amount of a*, b*, CO2, TSS and total counts increased (P<0.05). Also, with increasing the concentration of essential oils and alginates, the amount of acidity, carotenoids, ascorbic acid, L* increased and pH, weight loss, TSS, a*, b*, CO2 and total count decreased (P<0.05). Escherichia coli, mold and yeast count of the samples did not show any growth from the mentioned treatments until the 12th day. Overall, the Oliveria essential oil and alginate were effective in improving the properties of grated carrots under the modified atmosphere during storage. ConclusionThe study showed that Oliveria EO and alginate added to grated carrots in modified atmosphere packaging during storage was effective in reducing respiration, water loss, microbial load and increased the shelf life. Treatment containing 1.5% alginate and 250 ppm Oliveria EO showed the best chemical, microbial and sensory characteristics. The results indicated that by packing under modified atmosphere and coating by alginate and Oliveria EO, a new carrot product provided to the market with maintaining durability and quality characteristics during storage.
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