Efficacy of Liquid Smoke as an Ingredient in Hotdogs against Listeria monocytogenes and its Effects on the Microbial Shelf-life and Quality Attributes
Type of Degreedissertation
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Research was conducted to study the efficacy of a commercial liquid smoke as an ingredient in hotdog manufacture against L. monocytogenes as well as its effect on the microbial shelflife and quality attributes during storage. Chicken and pork hotdogs were made with 0, 2.5, 5 and 10% w/w liquid smoke as an ingredient along with spices. These hotdogs were inoculated with high (8 log10 CFU/ mL) or low (4 log10 CFU/ mL) levels of L. monocytogenes serotype 4b, vacuum packaged and stored at 4°C for up to 12 weeks. Sampling was conducted every week for 12 weeks to estimate growth of L. monocytogenes growth, spoilage microflora (aerobic plate counts, yeast and molds, lactic acid bacteria and total coliforms), sensory attributes and texture profile analysis. Liquid smoke was effective (p≤0.05) in reducing the growth of L. monocytogenes throughout the storage period as compared to the control (0% Liquid smoke) samples. Hotdogs made with 10% liquid smoke completely suppressed the growth of L. monocytogenes at high and low inoculum levels. On the other hand, growth of spoilage organisms below detection limit (7.5 CFU/mL) on all the treatments throughout the storage period indicated that the product was handled hygienically from manufacture to packaging. Addition of liquid smoke did not affect (p>0.05) the sensory properties of the hotdogs. Untrained panelists rated the products “like moderately” to “like slightly” for appearance, texture, juiciness, flavor and overall acceptability. They did not perceive differences (p>0.05) among the hotdog treatments as compared to the control samples throughout the storage period. Texture profile analysis indicated that incorporation of liquid smoke affected (p≤0.05) the texture and chewiness of the hotdogs. Although addition of 10% liquid smoke had a significantly greater hardness and chewiness than the control samples, taste test indicated that taste panelists were not able to detect the differences.