Musleh Uddin

Fish and Related Products

This chapter provides a summary of studies on seafood quality evaluation using near-infrared (NIR) spectroscopy and presents the future prospects for this method. NIR spectroscopy is applied to determine the chemical composition in minced raw fish samples used to make fishmeal. One of the groups of researchers investigated the utility of NIR spectroscopy as a means to quantify the diet of seals via analysis of feces. Five of the six calibrations could accurately and precisely quantify how much of a given dietary component the seal had eaten the previous day from an NIR scan of the feces. NIR spectroscopy is therefore potentially a viable way to quantify seal diets. NIR spectroscopy is also successfully employed to determine moisture and sodium chloride in cured, and cold smoked Atlantic salmon. NIR reflectance spectroscopy in the spectral range of 1000–2500 nm was also measured directly for brine from barrel-salted herring, to investigate the potential of NIR as a rapid method to determine the protein content. A partial least squares (PLS) regression model between selected regions of the NIR spectra and the protein content yielded a correlation coefficient of 0.93, and a prediction error of 0.25 g/100 g. A nondestructive visible/NIR spectroscopy technique is proposed to investigate whether fish have been frozen-thawed. Compared with dry extract spectroscopy by infrared reflection (DESIR), no extraction is needed, and no wastes are produced in visible/NIR (Vis/NIR) spectroscopy using a fiber-optic probe, which would be an eco-friendly instrumental technique.

Fresh or Frozen-Thawed Fish. Classification of fresh and frozen-thawed fish by dry extract spectroscopy by infrared reflection

Given the perishable nature of fish, extension of its shelf-life is a requirement of normal trading. However, frozen fish usually have a much lower market price than fresh fish, therefore the substitution of frozen–thawed for fresh fish is a significant authenticity issue. According to the Food and Agricultural Organization (FAO) and the Japan Agriculture Standard (JAS) regulations, labelling should state that the fish has been frozen and must not be refrozen. Several methods to discriminate between unfrozen and frozen fish or fillets have been reported. However, all the methods reported are either timeconsuming, destructive or have limitations for practical uses. During freezing and thawing of meat, ice crystal growth causes biochemical and physical changes which lead to disruption of cellular organelles and release drip juice. It might be possible to detect these changes in frozen–thawed fish meat, more specifically in juice level, by NIR spectroscopy. NIR spectroscopy is based on the electromagnetic absorption of organic compounds and is widely used in the food industry. Therefore, an attempt has been made to classify fresh and frozen–thawed fish by NIR spectroscopy, which is also known to be a non-destructive and rapid technique.