The impact of plant-based antimicrobials on sensory properties of organic leafy greens

Authors: JOSHI, KAMINI - Arizona State University; PARKS, PATRICIA - University Of Arizona; Friedman, Mendel; RAVISHANKAR, SADHANA - Arizona State University

Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2016
Publication Date: 8/31/2016
Citation: Joshi, K., Parks, P., Friedman, M., Ravishankar, S. 2016. The impact of plant-based antimicrobials on sensory properties of organic leafy greens. Food and Nutrition Sciences. 7(10):906-919. doi:10.4236/fns.2016.710090.

Interpretive Summary: The objective was to study the sensory attributes of organic leafy greens treated with plant antimicrobials and identify treatments liked by panelists. This study provides sensory information about plant antimicrobials that can potentially be used as organic sanitizers that could have the least impact on the organoleptic properties of organic leafy greens. Organic leafy greens treated with 0.1% cinnamon oil were the most preferred by panelists. This treatment had the least impact on the sensory properties of both spinach and lettuce, suggesting that cinnamon oil may be a good alternative to chemical sanitizers such as hydrogen peroxide. In general, treatments with essential oils were rated high for pungency and off-odor, while treatments with plant extracts were rated high for browning. Combination treatments of plant extracts with essential oils were the least preferred. Our results have shown that certain types of leafy greens such as baby spinach may have higher preference liking after washing with plant antimicrobials. Overall, this study will help identify plant antimicrobial treatments that have the least impact on sensory properties of organic leafy greens and therefore preferred by consumers. This research was supported by a NIFA-USDA Organic Research and Extension Initiative competitive grant.

Technical Abstract: Plant extracts and essential oils are well known for their antibacterial activity. However, studies concerning their effect on the organoleptic properties of treated foods are limited. The objective was to study the sensory attributes of organic leafy greens treated with plant antimicrobials and identify treatments liked by panelists. Organic leafy greens were treated with plant antimicrobials and their combinations in wash water for 2 min and stored at 4oC for 24 h prior to serving panelists. Antimicrobials evaluated include: 0.1% clove bud, lemongrass, oregano, or cinnamon essential oils; 0.1% carvacrol or citral; 3% grapeseed or apple extract; 10% or 7% olive extract; combination of essential oils with extracts; 3% hydrogen peroxide (H2O2); and untreated control. Randomized block design with affective test was used and 60 panelists were asked to evaluate each sample for preference liking based on a 9-point hedonic scale and for sensory attributes based on a 5-point hedonic scale. Changes in texture and color properties of leafy greens were measured using a Texture analyzer and a Chroma meter, respectively. Based on preference liking, the overall acceptability of spinach treated with 0.1% cinnamon oil was ranked the highest (7.5±1.4-moderetly liked) and the lowest was the combination of 0.1% oregano oil with 7% olive extract (4.4±2.5-slightly dislike). For lettuce samples, among all plant antimicrobials, treatment with 0.1% cinnamon oil had the highest preference liking (7.1±1.7-moderetly liked) and treatment with 0.1% oregano oil with 10% olive extract was the least preferred (2.3±1.7-very much dislike) by panelists. Treatment with 0.1% oregano oil and 10% olive extract had the highest rating for pungency, browning, off-odor, bitterness, and sourness for lettuce samples. For spinach samples, the impact on these attributes varied based on the type of treatment. Based on the 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). Based on the CIE LAB color schemes, treatment with 0.1% oregano oil in combination with 10% olive extract had the greatest impact on the color of iceberg lettuce with the lowest L*(44.5±6.2) indicating the darkest color. Results from this study will help identify plant antimicrobial treatments that have the least impact on sensory properties of organic leafy greens and therefore preferred by consumers.