This research was recently presented as a conference poster. The Spanish researchers froze mackerel fillets under 3 different freezing regimes and also had a chilled control. The water content and weight loss was determined, and IR spectra obtained from two types of NIR spectrometer (one being hand-held), followed by chemometric analysis. The results indicated that the NIR spectrometers could differentiate 100% between the chilled fillets and the frozen fillets subjected to different numbers of freeze/thaw cycles, which was attributed to the water content loss caused by the freeze/thaw cycles. The same change in spectra occurred when measuring (blind) thawed samples, as well as the changes caused by freezing in the physical muscle cell structure. In frozen samples, differences in spectra of previousy frozen/thawed and refrozen samples were as a result of scattering of light by the ice crystal structure caused by different freezing regimes.
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