CORROSION AND WEAR PROPERTIES OF MATERIALS USED FOR MINCED MEAT PRODUCTION

The risk of material degradation is present in minced-meat processing equipment. Corrosion, wear and tribocorrosion properties of commonly used steel materials for such processing equipment are therefore studied in detail. Corrosiveness of minced meat has been evaluated by potentiodynamic measurements. Combined sliding wear and corrosion conditions have been simulated in laboratory using a block-on-ring setup allowing for electrochemical measurements. Detailed information concerning the mechanism of possible material degradation is provided by these results, together with microstructural analysis and thermodynamic considerations. Areas of precaution are stated and new material solutions are suggested.

PRACTICAL APPLICATIONS

The presented results show the importance of investigating both corrosion and wear properties of materials used for processing food under tribocorrosive conditions. In meat mincing, the processing materials need to be wear resistant and at the same time corrosion resistant because of possible aggressiveness of the food product and cleaning procedures. The use of laboratory setups has made it possible to investigate a steel containing vanadium-nitride and carbide phases in respect of both corrosion and wear properties     

Modified Atmosphere Packaging of Fresh, "Ready-to-use" Grated Carrots in Polymeric Films

“Ready-to-use” grated carrots were packaged in different films (oxygen permeability from 950 to 22,000 cc/m²/day/atm at 25°C) and stored at 2, 6 or 10°C for 10 days. Gaseous atmosphere in packs and the following were monitored: lactic acid bacteria, yeast counts, exudate and potassium ion released, sugars, carotene, ethanol and lactic acid. The respiration rate of the packaged carrots was measured. Films with very low oxygen permeability resulted in anaerobic respiration, high leakage of potassium, and high lactic acid bacteria. With high-permeability films (between 10,000 and 20,000 cc/m²/day/atm at 25°C), grated carrots showed aerobic respiration and retained good quality. At 10°C, in carrots packed in the most permeable film, sucrose decreased markedly during storage. The gas permeabilities required for packaging grated carrots were evaluated in relation to storage temperature.     

The yeast flora of stored ready-to-use carrots and their role in spoilage

Spoilage of ready-to-use grated raw carrots packaged in polymeric films and stored at 10°C was investigated for involvement of yeasts. Cryptococcus albidus was only isolated during the first 3 days of storage, increasing to levels of 10⁵–10⁶g^-1. Candida lambica was more commonly isolated after 3–7 days of storage, and reached 10⁷–10⁸g^-1 after 12 days. Candida sake was present throughout storage, increasing from 10⁵–10⁶ after 3 days to 10⁷–10⁸ after 12 days. In some samples, Candida parapsilosis and Candida tropicalis were also isolated at levels similars to C. sake . All the yeasts isolated at the end of storage were fermentative species and their metabolism was characterized with a Warburg apparatus. Neither the number of yeasts nor the composition of the yeast flora were related to the deterioration of the product. Although Candida lambica inoculated on grated carrots caused spoilage after 12 days at 10°C, the high O₂ permeable film was most effective in reducing exudate.