Thermophilic Organisms Involved in Food Spoilage: Thermophilic Anaerobes not Producing Hydrogen Sulfide

Abstract

Clostridium thermosaccharolyticum is the type species of thermophilic anaerobes not producing H2S. This organism is obligately anaerobic and produces abundant gas from a variety of carbohydrates, giving rise to hard swell spoilage in canned foods. The organism occurs widely in nature and is found in numerous ingredients used in the manufacture of canned foods. Its growth temperature optimum is 55 C, with growth at 35–37 C if spores are first germinated at a higher temperature. The spores possess high heat resistance, a property which is complicated by the fact that their characteristic z value is often as low as 6.7 C, leading to underestimates of resistance by processes based on a z of 10 C. A medium consisting of peas in 2% peptone is the substrate of choice for detection and enumeration of the non-hydrogen sulfide producing thermophilic anaerobes. C. thermosaccharolyticum produces neither infections nor toxins, and therefore is of spoilage but not of public health significance. Survival of its spores in canned foods is of no consequence unless cans are inadequately coded and/or are stored at temperatures above 35 C for extended periods.