E: Food Engineering & Physical Properties Shrimp Processing Assessed by Low Field Nuclear Magnetic Resonance, Near Infrared Spectroscopy, and Physicochemical Measurements—The Effect of Polyphosphate Content and Length of Prebrining on Shrimp Muscle Mar´ ıa Gudj´ onsd´ ottir, ´ Asbj¨ orn J´ onsson, Arnlj´ otur Bjarki Bergsson, Sigurj´ on Arason, and Turid Rustad Abstract: The effect of using polyphosphates during prebrining and the effect of prebrining time of cold water shrimp (Pandalus borealis) was studied with low field nuclear magnetic resonance (LF-NMR) transverse relaxation time measure- ments (benchtop and unilateral) and near infrared (NIR) spectroscopy with the aim of improving shrimp processing. Strong calibrations were obtained for moisture content and water-holding capacity (WHC) using the NIR technique. Multivariate analysis indicated significant correlations between benchtop NMR parameters and moisture content and WHC, as measured with physicochemical methods and NIR spectroscopy. Significant correlations were also observed between NMR parameters and muscle pH, protein content, and phosphate content. The study showed that LF-NMR contribute to improved understanding of the shrimp brining process and to improved process control on-line or at-line, especially in combination with NIR measurements. However, optimization of the unilateral device is necessary. Keywords: cold water shrimp, low field nuclear magnetic resonance (LF-NMR), near infrared spectroscopy (NIR), polyphosphate, unilateral NMR Practical Application: Shrimp processing contains various steps that can lead to denaturation or aggregation of proteins, such as during cooking or freezing. Optimization of shrimp processing is therefore an essential task to ensure minimal moisture loss and to ensure a high quality of the final product. Traditional analytical methods for physicochemical measurements are, however, time-consuming, sample-destructive and expensive, and are, therefore, poorly suited for on-line or at-line process monitoring and optimization. The study showed the potentials of using LF-NMR and NIR spectroscopy for on-line or at-line process control during processing of cold water shrimp. The methods showed strong correlations to various physicochemical properties, such as muscle pH, moisture content, and WHC, which are important quality factors during shrimp processing. Moreover, the techniques are fast, reliable, and nonsample destructive and may therefore suit well for on-line or at-line applications. Introduction Shrimp are among the most traded seafood products in the world today (Oosterveer 2006). The commercial value and demand of frozen shrimp is ever increasing due to a competitive price and long shelf-life (Tsironi and others 2009). Optimization of shrimp processing is therefore an important task to answer this increased demand. Water is the most abundant component in muscle foods and changes in content and properties of water during processing in- MS 20101069 Submitted 10/13/2010, Accepted 1/30/2011. Authors Gudj´ onsd´ ottir, J´ onsson, Bergsson, and Arason are with Matis ohf. Icelandic Food and Biotech R&D, Value Chain and Processing, Vinlandsleid 12, IS-113 Reykjav´ ık, Iceland. Author Arason is also with Univ. of Iceland, Dept. of Food Science, Vin- landsleid 12, IS-113 Reykjav´ ık, Iceland. Author Rustad is with NTNU, Norwegian Univ. of Science and Technology, Dept. of Biotechnology, 491 Trondheim, Norway. Direct inquries to author Gudj´ onsd´ ottir (E-mail: mariag@matis.is). fluences the quality, texture, sensory attributes, and shelf-life of the product. It is therefore a major concern of seafood producers to retain the water, both for quality and economical reasons. During processing, the protein structure of a food is changed to various extents, affecting the characteristics of the final product. Cook- ing and freezing are examples of processing steps that are known to denature and cause aggregation of proteins and lead to loss of water from the muscle (Shenouda 1980; Steen and Lambelet 1997; Jensen and others 2002; Jensen and Jørgensen 2003). Pro- cessing of cold water shrimp includes various steps that affect the protein structure of the muscle, by chemical, physical, or mechan- ical treatment. Salts and phosphates are commonly used chemicals within shrimp processing to enhance water-holding properties of the muscle (Offer and Trinick 1983), to make peeling easier and to minimize yield loss during cooking and freezing (Crawford 1980; Goncalves and Ribeiro 2008b). Whether salts and phosphates are used prior or after cooking and peeling of the shrimp has a sig- nificant effect on the chemical composition and physicochemical C  2011 Institute of Food Technologists R  doi: 10.1111/j.1750-3841.2011.02112.x Vol. 76, Nr. 4, 2011  Journal of Food Science E357 Further reproduction without permission is prohibited