Abstract
The objective of this study was to investigate the effect of salt concentration on meat iridescence in cured cooked pork products. In addition, the influence of nitrite and pigmentary color on iridescence and its visual macroscopic perception was ascertained. Sample cubes from the pigs M. longissimus thoracis et lumborum were salted with either NaCl (20 g/kg, 40 g/kg) or nitrite curing salt (6 g/kg, 20 g/kg, and 40 g/kg) and subsequently cooked. Control samples were not salted. The effects of NaCl and curing salt on iridescence, instrumental color and microstructure were evaluated. Salt treatment significantly (p < 0.05) increased water-holding capacity, mean myofibers diameters and iridescence and reduced light scattering (L* value). An iridescence limit was reached with the 20 g/kg salt treatments. No differences between sodium chloride and nitrite curing salt were observed for both visual evaluation and colorimetry of the interference colors. Iridescence increases were attributed to a swelling of the myofilament lattice and thus reduction of intermyofibrillar spaces as well as an optical clearing of the myofibrils by dissolution of myofibrillar proteins that both reduce light scattering and allow more reflectance and interference to occur.Graphic abstract
Highlights
Meat color is one of the primary factors influencing purchasing decisions of consumers
All sample slices cut transversely to muscle fiber direction from the samples core showed iridescence to varying degrees, depending on the salt treatment (Fig. 3). This finding contradicts the hypotheses of iridescence originating from salt crystals on the product surface [9] and is in agreement with observations made by Wang [7] who found that iridescence could not be eliminated by removal of salt from the samples’ surfaces
These results agree with Wang [7] who reported that iridescence was found both in raw and cooked meat, and assumed that raw meat might have the same level of iridescence as cooked meat since the striation pattern of A- and I-bands is still visible after cooking [24, 25]
Summary
Meat color is one of the primary factors influencing purchasing decisions of consumers. Color defects, such as discoloration or iridescence, can be reasons for product rejections. With the most common iridescent colors being green and yellow [6], consumers are often concerned about product quality and safety of meat products. They misinterpret iridescence often as microbial spoilage or addition of undesired chemical additives even though it is a physical phenomenon that has no real negative bearing on product edibility [7]. A reduction in the occurrence of iridescence would be beneficial since it would lead to less high-quality meat products being discarded
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