Freshness indices, fish

Raatikainen, O., Reinikainen, V, Minkkinen, R, Ritvanen, T., Muje, R, Pursiainen, J., Hil-tunen, T., Hyvonen, R, von Wright, A., Reinikainen, S.R (2005) Multivariate modelling of fish freshness index based on ion mobility spectrometry measurements. Anal. Chim. Acta 544 128-134. 

Trimethylamine, Trimethylamine Fish, meat, fruits, Freshness index... 

Wen and Kuo (2001) indicated that application of high pressure (200 MPa, 12 h) resulted in a decrease in the total plate count of Tilpia fillets from 4.7- to 2.0-log CFU/g the freshness index of the product was also higher than the unpressurized sample. Ramaswamy et al. (2008) indicated that in the case of mackerel fish slurry, the D-values of E. coli were higher than those of L. monocytogenes at pressure levels equal to or greater than 350 MPa, while a reverse trend was observed... 

Handheld and portable systems may have less resolution and spectral range than laboratory systems but can be customized for specific applications with customized spectral libraries. Specialized applications for these instruments include measuring the freshness of fish by monitoring the concentration of dimethylamine, which is directly related to age and temperature of processed frozen fish (Herrero et al, 2004). Fat concentration, composition, and saturation index allows a handheld Raman instrument to determine in less than 1 min if edible oils such as olive oil have been adulterated or if cheaper oil is being sold as more expensive olive oil. 

A method similar to K value is the Kj value index that is used for freshness evaluation of fish that accumulate more inosine than hypoxanthine during spoilage (24). The K value is illustrated in Figure 3 (18,19,20,24). K is used with salmon, halibut, yellowtail, and numerous other tropical fish, while K value is reliable for catfish, white flounder, ocean perch, English sole, and various other species (24). The Kj value can be utilized for species specified for K value but not vice versa due to sensitivity of Kj value to the build up of hypoxanthine and not the total sum of degradation products as needed with K value (24). 

Biogenic amines have been used to establish quality indexes in various foods in order to signal the degree of freshness and/or deterioration of meat, fish, wines, and other foods and beverages (Mietz and Karmas, 1977 Hernandez-Jover et al., 1996a Ruiz-Capillas and Moral, 2001 Silva and Gloria, 2002 Vinci and Antonelli, 2002 Ruiz-Capillas and Jimenez-Colmenero, 2004 Ruiz-Capillas et al., 2007, 2011). A food with toxic levels of amines such as histamine or tyramine often appears organoleptically normal, like tuna or fermented chorizo, so that unacceptable and toxic levels of histamine are undetectable prior to consumption (Vidal-Carou et al., 1990 Lopez-Sabater et al., 1996). 

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