Changes in selected biochemical and sensory parameters as affected by the superficial inoculation of Penicillium camemberti on dry fermented sausages

Abstract

An atoxigenic strain of Penicillium camemberti was superficially inoculated on fermented sausages in an attempt to improve their sensory properties. The growth of this mould on the surface of the sausages resulted in an intense proteolysis and lipolysis, which caused an increase in the concentration of free amino acids, free fatty acids (FFA) and volatile compounds. Many of these were derived from amino acid catabolism and were responsible for the “ripened flavour”, i.e. branched aldehydes and the corresponding alcohols, acids and esters. The development of the fungal mycelia on the surface of the sausages also protected lipids from oxidation, resulting in both lower 2-thiobarbituric acid (TBARS) values and lipid oxidation-derived compounds, such as aliphatic aldehydes and alcohols. The sensory analysis of superficially inoculated sausages showed clear improvements in odour and flavour and, as a consequence, in the overall quality of the sausages. Therefore, this strain is proposed as a potential starter culture for dry fermented sausage production.

Introduction

Flavour development in cheese and cured fermented meat products is a complex process in which carbohydrate fermentation, lipid breakdown and proteolysis are the main pathways involved, as well as the further transformations of the substances formed in these reactions into volatile compounds Montel et al., 1998, Ordóñez et al., 1999.

Moulds belonging to the genus Penicillium genera are the most widespread in meat and derived products, probably because they can grow at lower temperatures and a_w than other moulds normally present in these products Corry, 1987, Northold and Soentoro, 1988. Penicillium camemberti is the white mould that forms the characteristic rind of some cheeses, such as Camembert and Brie, and is the main microorganism responsible for the flavour of these products. This organism is involved in proteolytic and lipolytic phenomena in cheese (Gripon, 1997) and in the latter transformation of the resulting free amino acids and fatty acids into important taste and aroma compounds such as ammonia, methyl ketones, primary and secondary alcohols, esters, aldehydes, lactones and sulphur compounds (Jollivet et al., 1993). Camembert cheeses develop a strong ammonia odour when overripened as a result of the intense deaminative activity produced by this mould (Gripon, 1997). Ammonia has a low odour threshold (5 mmol/kg) (Kubı́cková and Grosch, 1998a) and its presence is associated with a “ripened aroma” whenever its concentration is not too high.

In the last few years, the importance of amino-acid-derived molecules in the flavour of ripened food has been the subject of extensive investigations Möller et al., 1998, Smit et al., 2000. Amino acids can be transformed into amines, α-ketoacids or other amino acids via decarboxylation, deamination or transamination, respectively, by microorganisms growing in surfaced-ripened cheeses, e.g. Brevibacterium linens and Pseudomonas, and blue cheese, e.g. Penicillium roqueforti (Hemme et al., 1982). Some branched aldehydes, such as 2-methylpropanal and 2- and 3-methylbutanal, derived from valine, isoleucine and leucine, respectively, have also been associated with a “ripened aroma” in fermented sausages (Stahnke et al., 2000).

The objective of the present study was to enhance the formation of amino-acid-derived compounds by the superficial inoculation of an atoxigenic strain of P. camemberti in an attempt to potentiate the “ripened aroma” of dry fermented sausages, as well as to know the behaviour of a mould typically used in dairy industry on the sensory properties of these products.