Manuela Fernández

Proteolysis in dry fermented sausages: The effect of selected exogenous proteases

The effect of three commercial proteases (pronase E from Streptomyces griseus, aspartyl proteinase from Aspergillus oryzae and papain) on protein breakdown and the sensory characteristics of dry fermented sausages was investigated. Water soluble, non-protein, 5% phosphotungstic acid soluble, 5% sulphosalicylic acid soluble and total volatile basic nitrogen contents increased during fermentation, stabilizing later until the end of ripening (26th day). Nitrogen values were always greater in the aspartyl proteinase added batch in comparison with the other protease added batches. Total free amino acid changes showed a similar pattern to those observed for the 5% sulphosalicylic acid soluble nitrogen. The electrophoretic studies demonstrated that proteolysis of high molecular weight myofibrillar and sarcoplasmic proteins was more prominent in protease added batches. It was especially intensive in papain one. The dominant amino acids at the end of ripening were similar in all batches. Tyramine and histamine increased throughout ripening. No significant differences in sensory properties were found between control and pronase E and papain added batches, but they were significantly different (p < 0.01) from the sausages containing aspartyl proteinase, due to an excessive softening. The effect of exogenous enzyme addition on the flavour potentiation of dry fermented sausage is discussed.

The contribution of Penicillium aurantiogriseum to the volatile composition and sensory quality of dry fermented sausages.

An atoxygenic, proteolytic and lipolytic strain of Penicillium aurantiogriseum was tested for its ability to accelerate the production of volatile compounds and to improve the sensory properties of dry fermented sausages. The following batches of sausages were prepared: control; superficially inoculated with a spore suspension; added with an intracellular cell free extract; and superficially inoculated and added with the intracellular cell free extract. Higher levels of lipid oxidation products were found in the aroma extracts of sausages without a mould cover. In contrast, branched aldehydes and alcohols presented higher concentrations in superficially inoculated and extract added sausages, while esters only showed higher concentration in the first ones. The sensory analysis showed that sausages prepared with both treatments received the highest scores in all the properties evaluated, which demonstrated both the potential of this mould as producer of volatile compounds and the effectiveness of combining both treatments.

Microbial and physicochemical modifications of hake (Merluccius merluccius) steaks stored under carbon dioxide enriched atmospheres

Microbial counts (total viable, Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae), biochemical parameters [pH, total volatile nitrogen, nucleotide breakdown products, non-volatile amines, D(−) and L(+) lactic acid and short-chain fatty acids] and sensory attributes (colour and odour) of refrigerated (2 °C) hake (Merluccius merluccius) steaks under carbon dioxide enriched air (CO2 /air, 20/80 v/v and CO2 /air, 40/60 v/v) and air atmospheres were determined. When compared with air, sensory results showed shelf-life extension of 4 and 11 days for 20% and 40% CO2-enriched atmospheres, respectively. Microbial and biochemical results also revealed that the 40% CO2-enriched atmosphere was the most effective packaging type for refrigerated hake. © 2000 Society of Chemical Industry

Accelerated ripening of dry fermented sausages

Abstract Research on accelerated ripening of dry fermented sausages started in the early 1990s. Fermented sausages manufacture is a very important part of meat industry in many countries and the acceleration of ripening would result in a reduction of the storage time and would increase the profit margin and the competitiveness of the end product. The different strategies that have been assayed with this purpose include ripening at elevated temperature, use of genetically modified starter bacteria, addition of enzymes and addition of slurry systems. Over the last decade, numerous studies have been carried out, especially on the addition of enzymes. The aim of this paper is to review and update the knowledge on this topic. The more recent approaches in this field, such as the use of microbial extracts, are also presented.

Effect of the addition of pronase E on the proteolysis in dry fermented sausages

The effect of the addition of pronase E at two different concentrations on protein breakdown during the ripening of dry fermented sausage was studied. In all batches, water-soluble, non-protein and 5% phosphotungstic acid soluble nitrogens increased sharply during the first days of ripening, then became stabilized until the end of the process (26th day), and the total volatile nitrogen consistently increased during ripening. The greater the pronase E added the higher were the values reached for all these fractions. The changes in total free amino acids showed a similar pattern to that observed for the phosphotungstic acid soluble nitrogen. Histamine and tyramine progressively increased throughout the ripening. By sensory evaluation, no significant differences between the control batch and the batch with the lowest amount of added pronase E were found, but both batches were significantly different (P < 0·1) from the batch manufactured with the highest concentration of pronase E, which was classed as objectionable by the panellists because of its excessive softness.

Inactivation of Salmonella enterica serovar Enteritidis on shell eggs by pulsed light technology

This is a study on the efficacy of pulsed light (PL) technology for the inactivation of Salmonella enterica serovar Enteritidis on shell eggs. In preliminary studies on noble agar, a PL treatment of 0.7 J/cm(2) gave an inactivation of 6.7 log CFU/cm(2). Photoreactivation of Salmonella (0.5-0.7 log CFU/cm(2)) was observed. Different results were obtained in eggs according to the state of the cuticle. When unwashed eggs were pulsed, 24 to 80% of the samples showed the maximum decontamination (3.6 log CFU/egg), depending on the fluence applied. This maximum was not obtained on washed eggs, in which the highest reduction was 1.8 log CFU/egg with a fluence of 12 J/cm(2). PL can be a useful method for egg processing since the integrity of the cuticle is preserved, and requires that the treatment should be applied as soon as possible after laying and on unwashed eggs. As Salmonella has shown the capability of photoreactivation, it is advisable to keep eggs protected from light once they have been pulsed.

Use of carbon dioxide enriched atmospheres in the refrigerated storage [2°C] of salmon (Salmo salar) steaks

Abstract Selected microbial counts (total viable microbiota, Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae), biochemical parameters [pH, total volatile nitrogen, nucleotide breakdown products, non-volatile amines, d(–) and l(+)-lactic acids and short-chain fatty acids] and sensory attributes (colour and odour) of refrigerated (2  °C) salmon (Salmo salar) steaks stored under CO2-enriched [CO2/air (20/80, v/v), CO2/air (40/60, v/v)] and air atmospheres were determined. When compared with air, sensory results showed shelf-life extension of 6 days and 15 days for 20% and 40% CO2-enriched atmospheres, respectively. Microbial and biochemical results also revealed that the 40% CO2-enriched atmosphere was the most effective packaging type for refrigerated salmon.

Effect of the addition of pancreatic lipase on the ripening of dry-fermented sausages — Part 1. Microbial, physico-chemical and lipolytic changes

The effect of the addition of nine different amounts (3-500 units) of pancreatic lipase on the microbial and physico-chemical parameters and lipid fractions during the ripening of dry fermented sausages has been studied. No differences between conventional and lipase-added sausages were found for pH, dry matter and water activity. The addition of lipase caused a greater accumulation of products resulting from the triglyceride breakdown, mainly diglycerides and free fatty acids (FFA). The maximum rate of lipolysis was observed during the first week of the ripening process, specially in the fermentation phase. The greater the pancreatic lipase added, the higher lipolysis observed. At the end of the ripening, the levels of total FFA were clearly higher (1·5 to 5-fold) in all lipase-added batches than in the controls. This fact gave rise to the accumulation of a great amount of FFA, which can contribute either by themselves to the flavour of the sausage or can be available as substrates for further transformations which may generate other flavour compounds.

Effect of the Addition of Papain on the Dry Fermented Sausage Proteolysis

The effects of the addition of two different concentrations of papain on the proteolysis development and the sensory characteristics of dry fermented sausage were studied. In all batches, water soluble, non-protein, 50 g litre -1 phosphotungstic acid soluble, 50 g litre -1 sulphosalicylic acid soluble and total volatile basic nitrogens increased during fermentation (first 2 days). The changes were more pronounced and the values greater when the highest level of papain was added. After fermentation, nitrogen levels became stabilised until the end of ripening (26 days). The electrophoretic studies showed that the proteolysis of high molecular weight myofibrillar and sarcoplasmic proteins was more prominent in protease-added batches. A similar pattern was observed for free amino acids compared with that found in 50 g litre -1 sulphosalicylic acid nitrogen. Histamine and tyramine increased through ripening. Although the addition of papain increased the proteolysis phenomena, no improvement of the sausage flavour was observed in the sensory analysis.

Effect of the addition of pancreatic lipase on the ripening of dry-fermented sausages — Part 2. Free fatty acids, short-chain fatty acids, carbonyls and sensory quality

The effect of the addition of nine different amounts (3-500 units) of pancreatic lipase on the composition of free fatty acids (FFA), short-chain fatty acids and carbonyls, as well as the sensory quality, has been studied on dry fermented sausages. The lipase produced a greater release of all fatty acids in relation to the control sausages. The greater the pancreatic lipase content, the higher the release of these fatty acids, the most important ones being myristic, palmitoleic and oleic acids. A lower release of linoleic acid was observed, probably because of its oxidative degradation. At the end of the ripening in all lipase-added batches, a clear increase of the carbonyl content was noticed in relation to conventional sausages. No consistent changes were observed in the short-chain fatty acid fraction. In the sensory evaluation, the highest significant differences (P < 0·01) between control sausages and lipase-added batches were observed when 60 and 90 lipase units were used. According to the chemical and sensory analyses, it can be concluded that the addition of 60 and 90 units to sausages seems to be useful to enhanced the flavour of these products.