Control of lightness and firmness of cold and reheated frankfurter-type sausages using different spectroscopic methods applied to raw batter

Sammendrag

Muscle types and collagen, fat and protein devoid of collagen have been varied in frankfurter-type sausages made from beef and pork meat as well as pork backfat. The content of collagen was fixed at preset levels with pork rind. The amount of total muscle protein varied between 5.9- 11.9 % and the fat between 16.1-22.1%. The collagen content varied between 1.3 to 4%. Spectroscopic measurements (visible and near infrared reflectance spectra 1100-2500 nm; front-face autofluorescence emission spectra 360-600 nm) on raw batters were used to predict the amounts of biochemical components (total protein minus collagen, collagen and fat) plus the lightness (L*- values from Minolta Chromameter) and firmness (compression) of cold (22C) and reheated sausages (60C). Lightness of sausages was most accurately determined from the batter data measured with Minolta Chromameter or the autofluorescence measurement system. Firmness of cold sausages could be described by the amounts of biochemical components plus the type of muscle used in the sausage. The second-best approach was to use the shape of the near infrared spectra to determined firmness. This was possible as the shape of near infra red spectra depended on total protein content, and total protein content largely determined firmness of cold sausages. If the sausages were reheated to 60C, near infra red spectroscopy determined firmness of the sausages with a lower accuracy than a combined solution of fluorescence and near infrared spectroscopy. The two spectroscopic techniques should then be used to estimate the amount of biochemical components in the sausages. Once these components are known, firmness can be calculated from a model between the amounts of biochemical components and firmness. For reheated sausages, as opposed to cold ones, there was a need to differentiate between collagen and the other muscle proteins in order to determine firmness. This was optimally achieved by using both autofluorescence and near infrared spectroscopy.