The background of quality defects can be found in use of poor raw materials, in technological failures, and in storage abuses. Some of the more common faults are discussed below.
Color defects can be caused by insufficient amount or absence of curing salt by mistake, but mostly by smoking or drying failure. If sausages are smoked with wet surfaces or if surfaces are wet for long, brownish-grayish discoloration occurs, which is most of the time irreversible.
Odor defects can be caused if surface is wet for long, and yeasts as well as micrococci grow, making the surface slimy and malodorous. This slimy layer inhibits good adhesion of molds which can slip off easily. If raw material is not of good hygienic quality or ripening-drying is not done properly (too high temperature, too slow drying, inefficient starter culture, etc.) spoilage can occur with unpleasant odor and taste; health risk cannot be excluded either.
Flavor defects can be caused if product is too acidic (higher carbohydrate concentration, higher temperature for long) or rancid. This latter can occur if raw material was not fresh, if fat ingredients contain too high concentration of unsaturated fatty acids, drying and storage is done at too high temperatures and too long, no nitrite is used, and sausages are not smoked.
A properly manufactured mold-ripened dry sausage has an even mold layer, the sausage is without deformation, and slices are uniform in color and texture. The reason for uneven mold layers may be technological in nature (temperature and relative humidity unfavorable, inefficient mold starter), but in some cases molds with high cellulase activity decompose the cellulose casing and small parts of the casing come off with the molds.
Deformation is caused by inadequate drying (too rapid, mainly in the first period), resulting in case hardening that does not allow steady drying. Case hardening is not only a quality defect: as a consequence, spoilage and/or pathogenic microbes may grow because aw-reduction is slowed down significantly.
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