SHELF LIFE EXTENSION OF KANGAROO MEAT USING NATURAL ANTIMICROBIALS

The following information is from research that was done by Dr Yasmina Sultanbawa at the Queensland Alliance for Agriculture and Food Innovation, University of Queensland.

The harvesting of kangaroos for human and pet food consumption has become a significant domestic and export industry in Australia.

At present the pet food industry uses sulphites as a chemical preservative to extend the shelf-life of chilled kangaroo meat.

Sulphites cause thiamine deficiency in low body weight animals (including cats and dogs) and the ffects are exacerbated when the animals are exculsively fed a diet containing high concentrations of sulphite preservatives.

There is a consumer demand for additive free food and the trend is to use natural antimicrobils such as plant extracts as preservatives.  Certain plant extracts are also a rich source of antioxidants which can extend the freshness of the product by preventing oxidation.

OBJECTIVE

To assess the potential of using natural antimicrobils such as plant extracts and organic acids in extending the storage life of chilled kangaroo meat and as an alternative to sulphites as a chemical preservative.

METHODS

Freeze dried water extracts of kakadu and Queensland Davidson plum, lactic acid and citric acid were screened for antimicrobial activity against Staphylococcus aureus and Escherichia coli using a mictotitre assay and the minimum inbigitory concentration was determined.

Different mixtures of natural antimicrobials both in-house and commercial blends were incorporated into kangaroo mince using vacuum and MAP packaging conditions and shelf life was determined over a chilled storage period of 29 days.

Samples from each treatment were taken on storage days 1, 4, 11, 15, 20, 25 and 29 and tested for microbiological, colour, gas chromatography mass spectrometry and sensory analysis.

FINDINGS

Screening of antimicrobial efficacy of kakadu and Queensland Davidson plum with organic acids completed inhibited S. aureus and E. coli.

It retained redness during the storage period and was comparable with the fresh kangaroo mince.  The highest reduction in redness was observed in treatments with 0.2% Oregano essential oil and 0.1% Queensland Davidson plum + 0.1% kakadu plum + 0.25% lactic acid over the 29 day storage period for vacuum packed products.

The most effective treatments observed were with a combination of Queensland Davidson plum + kakadu plum + lactic acid with vacuum packaging at day 20.

GCMS results revealed an increase in alkenes, aldehydes, ketones and alcohols in all treatments in comparison to the fresh kangaroo mince sample.  The highest off-flavour volatiles are present in the control sample without any treatment, indicating that the quality deterioration in the control was the most rapid at chilled storage.

CONCLUSION

Natural antimicrobial blends, both produced in-house and commercially sourced, were effective in extending the shelf-life of fresh kangaroo mince meat at chilled storage temperatures.  Vacuum packaging was more effective in maintaining the quality of fresh kangaroo meat than MAP.  Even though the aerobic bacteria were within the critical microbiological limits the sensory quality of most treatments was not acceptable after 29 days of storage.