The Effect of Homogenisation and Storage on the Near-Infrared Spectra of Half Shell Pacific Oysters ( Crassostrea gigas
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The Effect of Homogenisation and Storage on the Near-Infrared Spectra of Half Shell Pacific Oysters (Crassostrea gigas) Thomas Madigan & Andreas Kiermeier & Miguel de Barros Lopes & Daniel Cozzolino
Received: 25 July 2011 / Accepted: 2 November 2011 / Published online: 25 November 2011 # Springer Science+Business Media, LLC 2011
Abstract The effect of sample homogenisation and storage on the near-infrared spectra of Pacific Oysters (Crassostrea gigas) has been assessed. On each day of storage (Days 0, 3 and 5), spectra were collected using a Fourier transform near-infrared reflectance spectrometer in reflectance mode between 833 and 2,630 nm from whole (n=20) and homogenised oysters (n = 20). The raw spectra were dominated by water- and fatty-acid-associated bands. Linear regression analysis of the water-associated absorbance bands occurring at 1,942 nm indicated that a physical or chemical interaction may be taking place within the oysters at or near Day 3, likely associated with transfer of liquids to and from oyster tissues. One-way analysis of variance of principal component scores and extended multiplicative scatter correction highlighted the water regions (O–H bonds) in whole oysters and the importance of N–H-related compounds in homogenised oysters throughout storage. These findings indicate the potential usefulness of near-infrared reflectance spectroscopy to monitor and evaluate degradation of oysters over time.
T. Madigan (*) : M. de Barros Lopes Sansom Institute for Health Research and School of Pharmacy and Medical Sciences, University of South Australia, GPO Box 2471, Adelaide, South Australia 5001, Australia e-mail: [email protected] T. Madigan : A. Kiermeier Food Safety Research, South Australian Research and Development Institute, Waite Campus, GPO Box 397, Adelaide, South Australia 5001, Australia D. Cozzolino The Australian Wine Research Institute, Waite Campus, PO Box 197, Urrbrae, South Australia 5064, Australia
Keywords NIR . Sample presentation . Moisture . Shelf-life
Introduction Freshly harvested oysters are savoured by consumers for their cucumber and melon-like aromas and flavours, together with characteristic aromas of the sea and a firm, elastic texture (He et al. 2002; Josephson et al. 1985). However, retailers are increasingly demanding that products possess long shelf-lives. Thus, an understanding of product spoilage is needed to estimate remaining shelf-life in order to minimise wastage and increase profits. The spoilage of oysters is complex and occurs via metabolic activities of microbial organisms as well as through biochemical reactions such as oxidation and enzyme activity (Ashie et al. 1996). Traditional methods to evaluate spoilage of oysters include microbial, biochemical and sensory evaluation techniques (Ashie et al. 1996; He et al. 2002; Aaraas et al. 2004; Cao et al. 2009). However, these techniques and methods are either time consuming or require specialist sensory panels; therefore, novel rapid approaches are required. Near-infrared reflectance (NIR) spectroscopy
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