Accelerated ripening of Manchego type cheese by added commercial enzyme preparation from Aspergillus oryzae

Biogenic amines in Portuguese traditional foods and wines

The presence of biogenic amines in foodstuffs is an important food safety problem because of the implication of these compounds in food intolerance and intoxication. The separation and quantification of biogenic amines in foods is normally performed by chromatographic techniques. This review contains descriptions of the quantification of biogenic amines in Portuguese traditional fermented and/or ripened foods and wines, including Protected Denomination of Origin cheeses, dry-cured sausages, and Portuguese wines (including Port wines), using different analytical methods based on high-pressure liquid chromatography (UV or diode array and/or fluorometric detectors) and gas chromatography (with a mass spectrometry detector). The evolution of biogenic amines during fermentation, ripening, aging, or storage of those products was also evaluated. Biogenic amine concentrations ranged widely within individual food items, and storage, transport, and handling conditions can influence to some extent the biogenic amines present and their concentrations. Traditional foods are an important part of the Portuguese diet, and a high intake of harmful amounts of biogenic amines from traditional Portuguese fermented foods is possible. However, extensive research is needed to extend the current limited database.

Enrichment of cheeses manufactured from cow's and sheep's milk blends with sheep-like species-related alkylphenols

Enhancement of concentrations of species-related sheep-like alkylphenols, p- and m-cresols and 3- and 4-ethylphenols, in experimental Manchego-type cheeses manufactured from cow's and sheep's milk blends (80:20) by using arylsulfatases was investigated. A food-grade arylsulfatase from Aspergillus oryzae (ATCC 20719) was produced using a stimulatory medium, and crude dried cells were used as the enzyme source. Exogenous arylsulfatases from Helix pomatia and A. oryzae were added to cheese curd, and the amounts of species-related alkylphenols were measured. Arylsulfatase from H. pomatia released limited amounts of alkylphenols in the cheese only when used at a high level. Arylsulfatase from A. oryzae released substantial amounts of alkylphenols during 2 months of ripening. The concentrations of alkylphenols in A. oryzae arylsulfatase-treated cheese were comparable to the previously reported levels present in aged Manchego-type cheeses manufactured from pure sheep's milk.

Effect of the activity levels of the added proteolytic enzyme mixture on free amino acids in ripening Ossau-Iraty cheese

A proteolytic enzymatic preparation (using one of three enzyme concentrations and, hence, one of three different enzymatic activity levels) was added (before clotting) to the milk used to manufacture Ossau-Iraty ewes'-milk cheese. The free amino acids were analysed by reversed-phase high-performance liquid chromatography and the sulphosalicylic acid-soluble N fraction was quantified by the trinitrobenzenesulphonic acid method for use as an index of proteolysis during ripening. Sensory analysis of the cheeses began after two months of ripening. Use of the enzymatic preparation increased the rate of release of amino acids in an amount proportional to the enzyme concentration employed. The effect of the preparation was more pronounced in the early months of ripening, with the differences in the free amino acid contents of the various batches decreasing as ripening progressed. Levels of certain free amino acids, such as taurine, tyrosine and valine, were virtually unaffected by the addition of the enzymatic preparation, whereas levels of such amino acids as serine, glycine, arginine and proline were reduced. Texture defects in the cheeses were observed, namely, reduced elasticity and creaminess and increased brittleness. Similarly, enzymatic treatment also gave rise to bitter flavours that were not characteristic of the normal taste and aftertaste of Ossau-Iraty cheese and these changes were proportional to the quantity of enzyme added.