Although chemical or physical reactions are occasionally responsible for sauerkraut spoilage, most defects are caused by microorganisms (Table 7-4). Defects are more likely to occur if the production conditions are not properly controlled, leading to deviations in the fermentation pattern.
The two most common factors that influence the fermentation and that may lead to quality defects are temperature and salt. If, for example, the temperature is too high (>30°C) or if too much salt is added (>3%), L. mesenteroides will be in hibited, heterofermentative end-products will be absent, and the flavor will be harsh. Worse yet, when prompt acid formation is delayed by high salt conditions (or pockets of high salt, due to uneven mixing), growth of salt-tolerant yeasts may occur. Growth of Rhodotorula sp. is a particular problem, due to the undesirable pink pigment this yeast produces.
If, in contrast, the temperature is too low (<10°C) or too little salt is added (<2%),various Gram negative bacteria, including Enterobacter, Flavobacterium, and Pseudomonas, may grow. Some of these bacteria are capable of producing pectinolytic enzymes that cause a "soft kraut" defect, resulting from pectin hydrolysis.
Finally, some strains of L. mesenteroides produce dextrans and other polysaccharides that give a slimy or ropy texture to the product. Other lactic acid bacteria, including L. plan-tarum, may produce capsular materials that cause similar texture defects.
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