Optimization of Antimicrobial Combined Effect of Organic Acids and Temperature on Foodborne Salmonella and Escherichia coli in Cattle Feed by Response Surface Methodology

Despite the importance of feedstuffs and feed ingredients in the food chain, few studies have analyzed the effectiveness of usual methods for the microbial decontamination of feeds. This work aimed to study the combined effect of temperature and organic acids (formic or lactic) on the inactivation of 10 isolates of Salmonella enterica and Escherichia coli obtained from vegetable feed ingredients, including cereals and other processed materials, in cattle feed. A central composite design was used with acid concentrations ranging from 0 to 0.2% (vol/wt) and temperatures from 50 degrees C to 70 degrees C. Second-order models were obtained to predict the survival inhibitions. The results reported in the present study indicate that temperature affects the survivability more significantly than acid concentration, whose effect was isolate dependent. However, after 2min of treatment, optimal microbial inhibitions were generally achieved at temperatures above 65 degrees C, using 0.1% formic acid or 0.2% lactic acid for Salmonella isolates and around 0.1% lactic acid or 0.2% formic acid for E. coli isolates, respectively. This work provides a set of guidelines helpful to reduce microbial contamination of feeds and highlights the importance of feed-ingredient monitoring to reduce pathogen contamination risk during feed processing.