Radio frequency plus heat for in-shell egg pasteurization

Abstract

Less than 3 % of the eggs in the United States are sold pasteurized because of the long thermal process (∼ 60 min). However, this represents a food safety risk because of the possible presence of Salmonella spp. inside the egg. This research studied the inactivation of S. typhimurium in in-shell eggs using the novel technology radio frequency (RF) to enhance their food safety, evaluating quality, presence of sub-lethally injured cells (SICs), and cell recovery (7 °C). Eggs were inoculated inside with S. typhimurium (10⁵ CFU/egg) and processed with RF (40.68 MHz, 35 W, 4.5 min) followed by hot water spray (H, 56.7 °C, 20 min). The studied quality attributes were yolk color, Haugh unit, yolk index, shell breakage strength, yolk and albumen pH, and albumen degradation. ANOVA one–way was used to find significant differences (α = 0.05). RF plus heat can pasteurize the eggs after 24.5 min (5-log reduction). No SICs were detected in any of the samples, and cells did not recover after five days of storage (Limit of detection <1 log CFU/g). Most quality attributes were like the control eggs. Albumen degradation showed a significant difference (p < 0.05) after processing. RF represents a potential option to ensure the safety of in-shell eggs, preserving their quality.

Industry relevance

Most in-shell eggs are sold unpasteurized worldwide with the potential risk of Salmonella spp. The conventional pasteurization process is a lengthy intervention that adds cost to the product and can damage the quality of eggs. Radio frequency plus heat pasteurization offers an alternative to pasteurizing in-shell eggs with a volumetric heating process that inactivates Salmonella cells inside the eggs and has minor effects on the quality of eggs. This technology is a novel option for the egg industry, providing high-quality and reasonably priced safe eggs.