EVALUATING THE EFFECTS OF ORGANIC SANITIZERS AND PLANT-ANTIMICROBIALS ON HARVESTING EQUIPMENT AND SENSORY PROPERTIES OF ORGANIC LEAFY GREENS

Abstract

Foodborne outbreaks associated with leafy greens are attributed to many factors including cross-contamination between harvesting equipment and leafy greens. The objectives of the first study were a) to evaluate the efficacy of organic sanitizers and plant antimicrobials on these tools, and b) to determine if modified designs of coring knives are easier to decontaminate in comparison to the original design. Recently plant extracts and essential oils are gaining popularity due to their antimicrobial properties and being viewed as natural compounds. Studies have shown that plants compounds have antimicrobial activities both in vitro and in foods. However, studies regarding the effects of these antimicrobials on the organoleptic properties of foods are limited. The objectives of the second study were to a) perform sensory analysis to identify plant extracts or essential oils with highest preference liking by consumers in organic leafy greens; b) identify the effects of these compounds on sensory attributes of treated organic leafy greens; and c) determine changes in firmness and color properties of treated organic leafy greens. In order to reduce the strong aroma and flavor characteristics associated with essentials oils and plants extracts, these compounds can be incorporated into edible films. Edible films are thin layer of films made using fruit or vegetable pulp containing plant antimicrobials. The main objective of the last study was to determine preference liking by consumers and changes in physical properties of organic baby spinach treated with antimicrobial edible films. Three different designs of coring tools were evaluated. Coring tools were inoculated with S. Newport and treated with one of the following: deionized water, 50 ppm bleach, 3% hydrogen peroxide, 5% Chico wash™, 0.1% Oregano oil, 0.4% SaniDate 5.0®, 3% fulvic acid, or 0.1% oregano oil for 5 min. The surviving Salmonella populations on the tools were determined by swabbing four different locations on the tools and plating onto xylose lysine desoxycholate (XLD) agar. After inoculation with Salmonella overnight culture (8 log CFU/ml), an average of 6.35 log CFU/cm² attached onto the original coring tool, 6.31 log CFU/cm² on modified design 1, and 6.26 log CFU/cm² on modified design 2 coring tools. When comparing the efficacy of sanitizers, 3% H₂O₂ had the highest reductions of 5.98±0.56-6.22±0.29 log CFU/cm² in Salmonella population. Treatments with 0.39% SaniDate 5.0® and 0.1% oregano oil were comparable (to hydrogen peroxide) which yielded reductions of 5.89±0.80-6.19±0.22 log CFU/cm² and 5.51±0.58-5.90±0.46 log CFU/cm², respectively. When comparing the four locations on these tools, the greatest reduction was seen at location 2/3 on all three designs of coring tools. Organic iceberg lettuce and baby spinach were washed with various essential oils, plant extracts, and their combinations in tap water for 2 min. After wash treatment, each sample was stored at 4°C for 20-24 h before performing sensory evaluation and measuring changes in physical properties (color and texture) of leafy greens. A randomized block design with an affective test was used and 60 panelists were asked to evaluate each sample for preference liking based on a 9-point hedonic scale where 9 was extremely liked and 1 not liked at all. Preference liking was evaluated for the following parameters: aroma, color, freshness, mouthfeel, flavor, and overall acceptability. Additionally, panelists quantified each sample using a 5-point hedonic scale for the following attributes: pungency, browning, bitterness, off-odor, and sourness. Changes in firmness values and color of leafy greens were measured using Texture Analyzer and Chroma meter, respectively. Similar procedure was followed for sensory analysis of baby spinach treated with antimicrobial edible films wherein the edible films were added to bagged spinach. Edible films were made from hibiscus, apple, or carrot pulp which included 0.5%, 1.5%, or 3% of carvacrol or cinnamaldehyde. Forty panelists were asked to evaluate each sample based on preference liking and identify intensity of sensory attributes (pungency, browning, bitterness, off-odor, and sourness). Changes in color and firmness values were measured for organic baby spinach treated with edible films in plastic bags.Sensory analysis showed that washing organic iceberg lettuce and baby spinach with 0.1% cinnamon oil had the highest preference liking (7-moderately liked) and the least impact on sensory attributes (1-not affected at all) of these leafy greens. Similar results were observed for spinach leaves treated with cinnamaldehyde containing edible films showing higher preference liking values in comparison to those treated with carvacrol containing edible films. Our results also indicated that essential oils had higher impact on the firmness values and plant extracts had higher impact on the color properties of leafy greens.For textural analysis, washing iceberg lettuce with 0.1% oregano oil in combination with 10% olive extract yielded the highest firmness value (F=783.1±53.8). For spinach, samples washed with 0.1% lemongrass oil in combination with 1% apple extract yielded the highest firmness value (F=939.30±35.2). Additionally, no significant difference (p≤0.05) was found in firmness or color values of baby spinach treated with edible films containing plant antimicrobials. Results from the coring tool study will provide alternative organic sanitizer options for washing these tools which are more effective than currently used chemical sanitizers such as bleach. Findings from the sensory study will help in identifying appropriate antimicrobial treatments for washing organic leafy greens. Additionally, use of edible films with essential oils may prevent the adverse effects due to the direct application of essential oils on organic leafy greens.