Recent Advances in the Recovery and Improvement of Functional Proteins from Fish Processing By-Products: Use of Protein Glycation as an Alternative Method Esther Sanmart´ ın, Juan Carlos Arboleya, Mar Villamiel, and F. Javier Moreno ABSTRACT: The recovery of proteins from fish by-products for their utilization as food ingredients is becoming of increasing interest in the food industry as they may possess good functional and nutritional properties. This article reviews the main processing methods, such as enzymatic hydrolysis, pH shifting, membrane filtration, and some emerging technologies, used for the recovery of proteins from fish processing by-products. The impact of these methods on the yield and, especially, on the functionality of the recovered proteins is discussed in detail. Consid- ering that there is a huge amount of fish by-products destined for nonfood use, one of the current challenges of the food industry is the development of technologies that allow the recovery of ingredients from the fish process- ing by-products with potential to provide new and natural sources of high-value functional ingredients for human consumption. In this sense, this review explores the potential use of the glycation reaction to increase the yield of proteins extracted from fish by-products, as well as the effect of this reaction on their functional and biological prop- erties. Introduction According to the FAO Fisheries and Aquaculture Dept.’s report, in 2005 about 75% (107.2 million metric tons) of estimated world ﬁsh production was used for direct human consumption, whereas the remaining 25% (34.4 million metric tons) was destined for nonfood uses (Table 1). Ninety percent of world ﬁsh production (excluding China) destined for nonfood purposes ends up as ﬁsh meal and oil, and the remaining 10% is largely utilized as a feed in aquaculture and for animals (FAO 2007). The percentages of processing by-products generated from commercial ﬁlleting of ﬁsh species such as cod, tuna, and trout are even higher, ranging between 60% and 70% (Chen and Jaczynski 2007). MS 20090085 Submitted 1/30/2009, Accepted 4/14/2009. Authors Sanmart´ ın and Arboleya are with AZTI-Tecnalia/Unidad de Investigaci´ on Alimentaria, Bizkaiko Teknologi Parkea, Astondo Bidea–Edif, 609, 48160, Derio, Spain. Authors Villamiel and Moreno are with Inst. de Fermentaciones Industri- ales, Consejo Superior de Investigaciones Cient´ ıﬁcas (CSIC), C/Juan de la Cierva 3, 28006, Madrid, Spain. Direct inquiries to author Moreno (E-mail: j.moreno@iﬁ.csic.es ). An increase in ﬁsh production as a consequence of a rise in demand for ﬁsheries products is expected during the next several years (Delgado and others 2003). This means that the volume of ﬁsh processing by-products will also increase and, therefore, that an improvement in the management of these by-products is urgently needed. In addition, new solutions for the utilization of by-products are much in demand from the industry, as it could potentially generate additional revenue and reduce disposal costs for these materials (Jespersen and others 1999). Similarly, current environmental regulations issued by many governments are en- couraging both the use of more ﬁsh raw materials and/or the use of recovery methods with low environmental impact. This may also contribute to a sustainable development since most stocks of wild ﬁsh are currently classiﬁed as fully exploited (Delgado and others 2003). For all these reasons, one of the current challenges of the food industry is the development of technologies that allow the recov- ery of ingredients from the ﬁsh processing by-products with: (1) improved yield for their use in traditional ﬁsh processing, and/or (2) potential to provide new and natural sources of value-added ingredients to be used as nutraceuticals or functional ingredients 332 COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY—Vol. 8, 2009 C  2009 Institute of Food Technologists R 