Volatiles produced by microorganisms isolated from refrigerated chicken at spoilage

Abstract

Volatile components present at spoilage of refrigerated chicken breasts were identified using high-vacuum-low-temperature distillation techniques followed by analysis with combined temperature-programmed gas chromatography and mass spectrometry. A comparison was made of the compounds detected from both irradiated and non-irradiated muscle stored at 2 and 10°C under both aerobic and anaerobic conditions. Isolates were randomly selected from the spoiled poultry, identified, and evaluated for their ability to produce volatile spoilage notes when grown on radiation-sterilized chicken. Several isolates that produced off-odors on sterile chicken breasts were examined. Twenty-two compounds were associated with spoilage. Some of the compounds found on both irradiated and unirradiated samples were considered to play only a minor role in the spoilage aroma or were present in low concentrations, since the aroma of spoiled irradiated chicken lacked the harsh odor notes typical of spoiled unirradiated chicken. Fifteen of the 22 compounds were considered to be unique to unirradiated, aerobically spoiled samples. Nine of these compounds, hydrogen sulfide, methyl mercaptan, dimethyl sulfide, dimethyl disulfide, methyl acetate, ethyl acetate, heptadiene, methanol, and ethanol, were found on chicken spoiled at both 2 and 10°C. Xylene, benzaldehyde, and 2,3-dithiahexane were detected only in samples stored at 20C and methyl thiolacetate, 2-butanone, and ethyl propionate were associated with 10°C spoilage. Fifty-eight isolates randomly selected from fresh, radiation-pasteurized, and unirradiated spoiled poultry were classified taxonomically, and 10 of them, which produced spoilage odors on sterilized chicken breasts, were selected for subsequent analysis of their volatiles. Isolates identified as Pseudomonas putrefaciens and Pseudomonas species that were members of groups I and II of Shewan's classification, as well as Flavobacterium and oxidative Moraxella, produced a number of the compounds found in the aroma of spoiled chicken. A total of 17 compounds were identified. Whereas no isolate produced all of the aroma compounds found in the aroma of spoiled chicken, together they did produce the nine found in unirradiated samples spoiled at either 2 or 10°C, as well as methyl thiolacetate and xylene. Six compounds were present in the volatiles produced by the isolates but were absent in the volatiles identified from spoiled chicken. These were hydrogen cyanide, methyl isopropyl sulfide, 2-propane thiol, methyl propionate, ethyl benzene, and an unidentified compound. The spoilage odor of meat, poultry, and fish at refrigeration temperatures is attributed mainly to microbial by-products (2, 10, 13, 15) and not to autolytic products from tissue (10, 13, 17). Whereas spoilage odors have been subjectively described (1, 14, 15), only recently have attempts been made to identify specific volatile compounds present at spoilage and relate them to the causative microorganism.

Volatile compounds produced by meat pseudomonads and related reference strains during growth on beef stored in air at chill temperatures

“…fragi reference strains is also entirely consistent with published taxonomic, chemical and sensory data. These organisms clustered together in numerical taxonomic studies (Shaw & Latty 1982;Molin & Ternistrom 1982) and ester production has long been regarded as a distinguishing taxonomic feature of the type species (Breed et al 1957), while publications associating growth of such organisms on food with 'fruity' odour development are numerous (Castell & Greenough 1959;Reddy et al 1968;Herbert et al 1971;McMeekin 1975;Freeman et al 1976;Daud et al 1979;Dainty et al 1984). It was therefore surprising to find that only 66% of the meat and reference strains studied produced esters, and that amongst those failing to d o so was Ps.…”

Occurrence of isopropylthio compounds in the aquatic ecosystem (Lake Neusiedl, Austria) as a chemical marker for Microcystis flos-aquae

“…It was used by Dainty et al [24] for a chemotaxonomic classification of different strains of Pseudomonas sp. when he discussed the taxonomic assignments in a work of Freeman et al [25]. The separation of M. flos-aquae and M. aeruginosa into two well-defined species is also justified by the observation that, so far, the neurotoxicity has been exclusively found in blooms of M. aeru-ginosa, though the toxicity is not always expressed [20,21].…”

Review: Application of science and technology to poultry meat processing

“…Consequently, a number of studies have been directed towards relating 'off' odour to the volatiles produced by spoilage bacteria. Among these volatile substances are sulphides, esters, alcohols and ketones (Freeman et al, 1976;Pittard et al, 1982). Some of these, such as hydrogen sulphide, dimethyl sulphide and methanol, were considered to be associated with the typical 'off' odour of chicken breast meat undergoing spoilage at refrigerated temperatures, but it was not established that the compounds were produced in large quantities prior to spoilage.…”