Cabbage

Sauerkraut is pickled cabbage (Brassica oleracea). The cabbages of choice will have large heads (8-12lb) that are compact (dense), contain few outer green leaves and have desirable flavour, colour and texture. They are bred for yield, pest resistance, storability and content of dry matter.

Cabbages are increasingly harvested mechanically and are graded, cored, trimmed, shredded and salted. Their water content is about 30% and shredding is to a diameter of approximately 1 mm.

The shredded cabbage is soaked in brine in reinforced concrete tanks of capacity 20-180 tons and loosely covered with plastic sheeting. Alternatively, cabbage may be dry salted to about 2% by weight and allowed to self-brine through its own moisture. The cabbage is distributed to a slight concave surface and water put on top of the plastic cover to anchor it and ensure that anaerobic conditions can develop. Fermentation can take some 3 weeks, ideally at temperatures below 20°C.

Lactic acid bacteria constitute a relatively small proportion of the total bacterial count and comprise five major species: Enterococcus faecalis, Leuconostoc mesenteroides, Lactobacillus brevis, Pediococcus cerevisiae and Lb. plantarum. Despite their low levels, these organisms represent the most significant contributor to the fermentation. A low salt concentration (ca. 2%) and the low temperature (18°C) favour heterofermentative organisms. Conversely, a high salt content (3.5%) and high temperature (32°C) promote homofermentative fermentation. The normal sequence is heterofermentation first, followed by homofermentation. The main sugars in cabbage are glucose and fructose and, to a lesser extent, sucrose. They are converted to acetic acid, mannitol and ethanol in the first week, together with CO2 which is important for establishing anaerobiosis. After a week or so, the brine becomes too acidic for the heterofermentative organisms and the fermentation is continued by the homofermenters, notably Lb. plantarum. Production of lactic acid continues until all the sugars are consumed and the pH has dropped from around 6 to 3.4.

The cabbage stays in the tanks until more than 1% lactic acid has been produced (30 days or more). The material is then either stored in the same vessel or is processed at this stage to the finished product.

The sauerkraut is removed either manually or by mechanical fork and is packaged into can, glass or plastic. Sodium benzoate (0.1% w/v) may be added as a preservative and the material stored at 4°C. If canned, the product is pasteurised and no preservative is added. Pasteurisation is at 74-82°C for 3 min. Heating is by steam injection or immersion and the product hot filled into cans.

Sauerkraut can be spoiled by Clostridia if the latter proliferates in the early stages of the process. Other potential problem organisms are oxidative yeasts and moulds. Discoloration may arise not only from the oxidation of cabbage components but also from the action of Rhodotorula which generates a red hue.

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