Salmonella Growth during the Soaking Step of ‘Sprouted’ Grain, Nut, and Seed Production

Abstract

Food companies are marketing products with “sprouted,” “activated,” or “awakened” ingredients. The label implies that germination of grains, nuts, and seeds confers improved health benefits; however, the “sprouting” process consists of a simple overnight soak in water often at ambient temperature, followed immediately by drying and further processing. Our objective was to quantify Salmonella growth during soaking of grains, nuts, and seeds commonly included in “sprouted” products. Raw grains (buckwheat, millet, quinoa, rice), nuts (almond, cashew, hazelnut, peanut, pecan, walnut), and seeds (flax, hemp, pumpkin, sunflower) were inoculated with Salmonella to achieve ~3 log CFU/g after drying. Inoculated samples (20 g) were soaked in water (20 mL) with incubation at 7 or 25°C for 24 h. Salmonella bacteria were enumerated using serial dilution and spread plating on Hektoen enteric agar (37°C, 24 h). Salmonella was capable of significant growth (> 3 log CFU/g) in all 15 grains, nuts, and seeds during ambient temperature soaking, reaching an average concentration of 7.05 log CFU/g. High salt concentrations (> 10%) and refrigeration (< 7°C) were verified to prevent growth of Salmonella during soaking. This study demonstrates the risk of ambient temperature “sprouting” practices and presents practical strategies to improve safety