CHANGES IN COLOR AND MYOGLOBIN OF MINCED BEEF MEAT DUE TO HIGH-PRESSURE PROCESSING

Minced beef meat was packaged under vacuum, air or oxygen, and pressur ized at 10 degrees C for 10 min. L colour values increased significan tly in the range 200-350 MPa, the meat becoming pink, while a values decreased at 400-500 MPa, the meat becoming grey-brown. Simultaneously , total extractible myoglobin decreased in the range 200-500 MPa, whil e the proportion of metmyoglobin increased at the expense of oxymyoglo bin at 400-500 MPa. Pressurization did not significantly increase the extractability of heme iron by an acid solution. Packaging of meat und er vacuum with an oxygen scavenger partly protected meat colour, since samples processed at 400 MPa became pink, without any change in a va lue or metmyoglobin content. Blending chilled minced meat with NaNO2 ( and NaCl) 18 h before processing at 350-500 MPa afforded a similar pro tection. Cysteine, ascorbic acid, nicotinamide or nicotinic acid had n o protective effects. Meat discoloration through pressure processing m ay result from (1) a 'whitening effect' in the range 200-350 MPa, due to globin denaturation and/or to heme displacement or release, and (2) oxidation of ferrous myoglobin to ferric metmyoglobin, at or above 40 0 MPa. Only the latter phenomenon is prevented by total oxygen removal or prior formation of nitrosomyoglobin. (C) 1995 Academic Press Limit ed