The use of oxygen scavengers to prevent the transient discolouration of ground beef packaged under controlled, oxygen-depleted atmospheres.

Rates of O(2) absorption from air were determined for a type of commercial O(2) scavenger that is formulated for rapid O(2) absorption at chiller temperatures. Rates of O(2) absorption from N(2) atmospheres containing 600 ppm O(2) were determined for trays that each contained 350 g of ground beef. Packs with controlled atmospheres of N(2) that contained ground beef and O(2) scavengers were prepared, to determine the conditions under which the scavengers could prevent the transient discolouration of the meat which arises from its reaction with the residual O(2) initially present in pack atmospheres. The rates of O(2) absorption by individual scavengers varied from the average by ±50%. The rate of O(2) absorption declined with decreasing oxygen concentration, from an average value per scavenger of about 12 ml h(-1) when O(2) concentrations were between 20 and 10%. At O(2) concentrations <1% (10,000 ppm) the rate of O(2) absorption was directly proportioned to the O(2) concentration so that the O(2) concentration in an atmosphere in a gas-impermeable pouch declined exponentially with time. The absorption of O(2) by ground beef was similarly dependent on the O(2) concentration. At 2 °C, the transient discolouration of beef in atmospheres initially containing about 50 ppm O(2) was prevented by the presence of 17.5 scavengers per l of atmosphere. At -15 °C, discolouration was prevented by 5 scavengers per l. The findings indicate that the O(2) concentration in pack atmospheres has to be reduced below 10 ppm within 30 min at 2 °C, or 2 h at -1.5 °C if ground beef is not to transiently discolour. It is unlikely that the required rates of O(2) absorption could be obtained economically with currently available, commercial O(2) scavengers. Copyright © 1995. Published by Elsevier Ltd.