RAMAN APPLICATIONS IN FOOD ANALYSIS - Raman Spectroscopy for Soft Matter Applications - page 206

reversible conformational change, expressed in decreased occurrence
of random coil and β -turn secondary structure and an increase in

α -helical content within the extended tissue. Furthermore, these

changes also infl uence specifi c amino residues within the microfi brils,
including changes in hydrogen bonding status and domain- domain
interactions [20] .
The use of Raman spectroscopy for the prediction of meat quality
as expressed by the water-holding capacity (WHC) of fresh meat from
pigs has also been explored [21]. WHC is an important quality trait for
the meat industry, because meat is sold by weight including the con-
tained water, and because WHC infl uences the appearance and sensory
properties of the product. The reduction in WHC during slaughtering
is infl uenced by pH and ongoing rigor development. The pH can be
manipulated by preconditioning the animals with adrenaline and exer-
cise; hence, the meat quality can vary as a consequence of the treatment
of the animals before slaughtering. The preliminary result showed that
Raman spectra had good potential for predicting the water drip loss in
the meat samples with low prediction errors and correlation coeffi -
cients above 0.95. The most informative Raman regions contained N −

H stretching of primary amides in proteins (3140 cm − 1 ) and the - helical

940 - cm − 1 band, which both might indicate partial protein denaturation.
The application of Raman spectroscopy to the fresh meat using a blue
632-nm HeNe laser resulted in good, well-resolved spectra, and it was
found useful to employ sharp aromatic ring breathe vibration at
1000 cm − 1 (Figure 8.3 ) as an “ internal standard ” for normalizing the
Raman spectra. It was concluded that the Raman observations suggest
coherence between WHC and pH, glycogen level, and protein
conformation.

α

8.4.5 Inorganics

Another interesting and useful feature of Raman spectroscopy is the
extraordinarily sharp spectra of inorganic compounds such as carbon-
ate minerals, which give rise to sharp, characteristic, and intense Raman
bands. The shape and precise wave number of this peak are character-
istic for the type of carbonate and can thus be used to identify the
polymorphic form. This was employed in the studies of “white spots,”
which develop on frozen shrimp shell during Atlantic storage [22,23] .
The most intense peak in the carbonate Raman spectrum of the white
spots was due to the totally symmetric carbonate CO stretch at 1086 cm − 1
(Figure 8.3). In the study, the presence of the white spots was fully
explained by the presence of α -chitin and calcium carbonate. It was