Determination of the myoglobin states in ground beef using non-invasive reflectance spectrometry and multivariate regression analysis

•Reflectance Spectrometry is used to determine OMb, DMb and MMb in ground beef.•The prediction error is higher in ground beef model than in whole steaks model.•Regression coefficients from the two models are different for OMb, DMb and MMb.•Calibration model of whole steaks cannot be applied to ground beef.

Seventy-two samples of ground beef from M. semimembranosus of two 5 and two 1.5 year old animals were prepared. Two types of fat tissues from either beef or pork were added to the ground beef. The samples were prepared to contain predominantly deoxymyoglobin (DMb), oxymyoglobin (OMb) and metmyoglobin (MMb) states on surfaces using selected methods based on chemical treatment (for MMb) and oxygen pressure packaging to induce the two other states. Reflectance spectra were measured on ground beef after three storage times. Partial least regression analysis was used to make calibration models of the desired myoglobin states. Validated models using leave-one-sample out cross validation gave, after correction and normalization, prediction errors of about 5%. Long term storage of ground beef was unsuitable for preparing pure MMb states due to gradual reduction of the pigment to DMb, presumably by bacteria.