Antimicrobial Activity of Coffee Husk Extracts aginst Listeria monocytogenes and Salmonella Typhimurium in Microbiological Media and Milk
Year: 2024
Type: dissertation
Abstract: Pathogenic bacteria pose significant challenges to food safety in the United States and globally.Salmonella enterica serovar Typhimurium and Listeria monocytogenes are among the pathogens that frequently trigger foodborne illness outbreaks, leading to substantial economic losses and public health burdens.Consumption of food contaminated by these bacteria, such as raw milk, can result in various gastrointestinal symptoms, ranging from mild discomfort to severe, life-threatening conditions.With the rise of antibiotic-resistant strains, it is crucial to explore alternative antimicrobial agents.Coffee, particularly the species Coffea arabica (yellow) and Coffea liberica (red) grown in Hawaii, represents a significant cash crop.The coffee cherries, the fruit of coffee trees, is considered a superfood due to its skin and juice, rich in bioactive compounds.However, the wet coffee seed comprises only approximately 55% of the fruit, leaving the other half of the coffee fruit (coffee husk) underutilized or considered a by-product of coffee production.This study aimed to assess the antimicrobial efficacy and mechanism of action of coffee husk against S. Typhimurium and L. monocytogenes.Coffee husk samples were obtained from the Island of Hawaiʻi and Oʻahu, and bioactive compounds were extracted using 80% acidified methanol.The total phenolic content of the extracts was quantified, and other chemical analyses, such as pH, sugar content, titratable acidity, and anthocyanin content, were conducted.The pH values of red and yellow coffee husk extracts were 4.10 and 4.18, respectively.The sugar and titratable acidity ratios for red and yellow coffee husk extracts were 9.60/1.55°Brix/% and 8.87/1.41°Brix/%, respectively.The total phenolic content of red and yellow coffee husk extracts was 5058.27GAEmg/L and 4600.27GAEmg/L, red nor yellow coffee husk extract at 25 mg/mL showed a significant effect on L. monocytogenes or S. Typhimurium in milk stored at 7°C, whereas 12.5 mg/mL red and yellow coffee husk extracts reduced the growth of these pathogenic bacteria in milk at 21°C.Moreover, both coffee husk extracts at 25 mg/mL completely suppressed L. monocytogenes and S. Typhimurium in milk during storage for up to 72 hours.In conclusion, coffee husk extracts exhibit strong antimicrobial effects on L. monocytogenes and S. Typhimurium but not on tested probiotic bacteria.The extracts can damage the cell membrane of these pathogenic bacteria and cause the leakage of intracellular proteins.They can also reduce biofilm formation by S. Typhimurium.Coffee husk extracts offer a potent and natural alternative to traditional food preservatives for enhancing the microbiological quality and safety of food.
Author: He, Yu
Language: English
Subfield: Food Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W6989408193