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EFFECT OF COOKING ON THE CHEMICAL COMPOSITION OF LOW-ALT,
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LOW-FAT WAKAME/OLIVE OIL ADDED BEEF PATTIES WITH SPECIAL
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REFERENCE TO FATTY ACID CONTENT
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I. López-Lópeza, S. Cofradesa*, V. Cañequeb, M.T. Díazb, O. Lópezb, F. Jiménez-
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Colmeneroa
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Instituto de Ciencia y Tenología de Alimentos y Nutrición (formerly Instituto del Frío)
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(CSIC). C/ José Antonio Novais, 10. 28040. Madrid. Spain.
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b
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Spain.
INIA (Ministerio de Educación y Ciencia). Ctra. A Coruña Km. 7.5. 28040. Madrid.
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*Corresponding author:. Instituto de Ciencia y Tenología de Alimentos y Nutrición
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(formerly Instituto del Frío) (CSIC). C/ José Antonio Novais, 10. 28040. Madrid. Spain.
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Tel: +34 91 549 23 00
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Fax: + 34 91 549 36 27
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E-mail: scofrades@ictan.csic.es
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1
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Abstract
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Changes in chemical composition, with special reference to fatty acids, as
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affected by cooking, were studied in low-salt (0.5 %)/low-fat patties (10 %) with added
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Wakame (3 %) and partial or total replacement of pork backfat with olive oil-in-water
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emulsion. The addition of Wakame and olive oil-in-water emulsion improved (P < 0.05)
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the binding properties and the cooking retention values of moisture, fat, fatty acids and
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ash, which were close to 100 %. Partial and total replacement of animal fat with olive
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oil-in-water emulsion reduced (P < 0.05) saturated fatty acids (SFAs), while total
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replacement also reduced (P<0.05) polyunsaturated fatty acid (PUFAs) contents. The
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fatty acid concentration in cooked patties was affected by product formulation. Unlike
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the case of all animal fat patties, when olive oil was added the cooking process
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increased (P < 0.05) SFAs, monounsaturated fatty acids (MUFAs) and PUFA n-3
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(linolenic acid) and n-6 (linoleic acid) contents. Cooked formulated patties with
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seaweed and partial or total replacement of pork backfat by oil-in-water emulsion and
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with seaweed added were less calorie-dense and had lower SFAs levels, while samples
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with olive oil had higher MUFAs levels.
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2
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Introduction
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Meat and meat products are important sources of many essential nutrients and
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contribute considerable proportions of the dietary intakes of various nutrients that are
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essential for optimal growth and development. However, consumption of some meat
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constituents (e.g. fat, saturated fatty acids-SFAs, cholesterol, sodium, etc.) has been
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associated with a higher risk of major chronic diseases in our society (e.g. ischaemic
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heart disease, cancer, hypertension and obesity) (Hulshof et al., 1999; McAfee et al.,
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2010; Williamson, Foster, Stanner & Buttriss, 2005). Changes in consumer demand and
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growing market competition have prompted a need to improve the quality and image of
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meat and meat products through the development of products with beneficial- health
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properties. This approach is of particular interest in the case of products like burgers or
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patties, since they are common meat products, widely accepted in certain population
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groups, and it is possible to easily induce changes of composition to improve their
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nutritional value and their potential beneficial- health properties (López-López,
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Cofrades, Yakan, Solas, & Jiménez-Colmenero, 2010).
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Because seaweeds are potential sources of some nutrients and bioactive
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phytochemicals, recent reports suggest that their use as food ingredients opens up new
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possibilities for the development of functional foods (Bocanegra, Bastida, Benedi,
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Rodenas, & Sánchez-Muniz, 2009; Fleurence, 1999), including meat-based functional
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foods (Cofrades, López-López, Solas, Bravo, & Jiménez-Colmenero, 2008). Different
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seaweeds have been used in the formulation of various types of meat products (Chun,
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Park, Park, Suh, & Ahn, 1999; López-López, Cofrades, & Jiménez-Colmenero, 2009a;
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López-López, Cofrades, Ruiz-Capillas, Jiménez-Colmenero, 2009b). Wakame (Undaria
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pinnatifida) seaweed is particularly promising as a meat ingredient due to its
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composition (dietary fibre, minerals, etc.) and technological properties (Cofrades et al.,
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2008; López-López et al., 2009a).
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Lipids are among the bioactive components (functional ingredients) that have
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received most attention, particularly in connection with the development of healthier
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meat products (Jiménez-Colmenero, 2007). Although Wakame has a healthier lipid
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profile, in view of its low lipid content, addition of this whole seaweed to meat products
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does not cause any appreciable improvement in their lipid profiles (López-López et al.,
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2009c). Therefore other strategies are necessary to produce healthier lipid formulations
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in meat products. Healthier lipid meat products have been developed by substituting
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animal fat with vegetable oils to produce a food more in line with health
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recommendations. This entails reducing SFAs and cholesterol and increasing
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monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). Of
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vegetable oils, olive is the one that has received most attention, chiefly as a source of
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MUFAs (mainly oleic acid). Partial substitution (in various percentages) of pork backfat
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by olive oil (as a liquid or as an oil-in-water emulsion) has been tried in various cooked
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and cured meat products (Bloukas & Paneras, 1993; Koutsopoulos, Koutsimanis, &
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Bloukas, 2008; Lurueña-Martínez, Vivar-Quintana, & Revilla, 2004; Muguerza,
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Gimeno, Ansorena, Bloukas, & Astiasarán, 2001; Paneras & Bloukas, 1994).
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In this context, our research group recently formulated healthier low-salt (0.5%),
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low-fat (10%) beef patties with added Wakame seaweed (3%) and partial or total
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replacement of pork backfat with an olive oil-in-water emulsion (López-López et al.,
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2010). The results showed that Wakame can be used as a potential functional ingredient
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in low-salt beef patties to overcome the technological and sensory problems associated
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with low-salt products. Also, Wakame supplies fortified patties with considerable
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amounts of dietary fibre (~ 6% of the recommended daily dietary fibre intake in 100 g
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of product) and minerals such as Ca, Mg and K (> 15% recommended daily amount in
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100 g) while maintaining a normal Na content and a low Na/K ratio. Replacement of
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pork backfat by olive oil emulsion improved the appearance and juiciness of the patties,
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while on the nutritional side the resulting product was healthier in terms of the amount
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and quality of the fat. The benefits of replacing SFAs with MUFAs derive from the fact
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that some SFAs (< 18-carbon atoms chain length) raise total blood cholesterol and low-
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density lipoprotein (LDL) levels and the high-density lipoprotein (HDL)/LDL ratio,
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which are associated with a high risk of cardiovascular disease, while MUFAs reduce
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the level of plasma LDL cholesterol without depressing the strong anti-atherogenic
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activity of HDL-cholesterol lipoproteins (Matsson & Grundy, 1985). Also, these
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products thus presented good technological, sensory and nutritional properties.
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Beef patties, like other foods, will normally be cooked prior to consumption, and
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that in itself may affect composition. Varying amounts of different meat components
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(water, fat, minerals) are lost during cooking of meat products, and these losses can
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significantly affect fat (fatty acid content) consumption and energy intakes (Badiani,
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Stipa, Bitossi, Gatta, Vignola, & Chizzolini, 2002; Librelotto, Bastida, Serrano,
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Cofrades, Jiménez-Colmenero, & Sánchez-Muniz, 2008; Serrano, Librelotto, Cofrades,
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Sánchez-Muniz, & Jiménez-Colmenero, 2007; Sheard, Nute, & Chappell, 1998).
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Although olive oil has been added to pork patties in liquid form (Hur, Jin, & Kim, 2008)
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and to beef patties stabilized in an oil-in-water emulsion (López-López et al., 2010), the
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authors have found no reports dealing with to the effect of cooking on the chemical
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composition of these kind of reformulated products. Cooking-induced modifications
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need to be considered in order to achieve a more realistic assessment of the potential
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nutritional/functional benefits of foods, and particularly of healthier meat products.
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The objective of this study was therefore to determine how cooking affects the
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chemical composition, with particular reference to the fatty acid profile, of healthier
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low-salt (0.5%), low-fat (10%) beef patties with added Wakame seaweed (3%) and
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partial or total replacement of pork backfat with olive oil-in-water emulsion.
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2. Materials and methods
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2.1. Raw materials and beef patties preparation
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Lean beef (moisture 74%, protein 21%, fat 3.5% and ash 1.3% ???), pork
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backfat (moisture 7,32%, protein 3,97%, fat 88,70%), Wakame seaweed (Undaria
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pinnatifida), olive oil (13 % SFAs, 79 % MUFAs and 8 % PUFAs) and the other
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additives used in meat product formulations were described by López-López et al.
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(2010). The Wakame composition (protein 11%, fat 1.0% and ash 37% on dry matter;
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39 % SFAs, 15% MUFAs and 46% PUFAs) was reported by Cofrades et al., 2008.
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The formulated beef patties studied were those described by López-López et al.
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(2010). Six different products (Table 1) were prepared to obtain 16.5 % of meat protein
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(from both lean beef and pork backfat) in all treatments. Pork backfat was added to the
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control sample (C) to give 10 % fat content (all animal fat from meat and pork backfat).
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In order to achieve a healthier lipid formulation, pork backfat was partially or totally
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replaced with olive oil-in-water emulsion. Partial replacement sample (PE) was
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formulated with 5 % animal fat and 5 % olive oil-in-water emulsion; total replacement
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sample (TE) was formulated with 10 % olive oil-in-water emulsion (no pork backfat
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added). Three additional samples were manufactured with the same lipid formulation,
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and 3 % (dry matter) added Wakame seaweed (W, WPE and WTE). All products were
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made with 0.5 % NaCl.
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The formulated patties (85 g) were placed in plastic bags (Wipak7gryspeert,
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PAE 110KFP), frozen at -25 °C in a Sabroe “Benjamin” model horizontal plate freezer
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(Hanst-Moller, Germany), vacuum packed and stored at -20 ± 2 ºC until analysis
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(within 2 weeks of preparation).
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2.2. Cooking method and thawing and cooking losses
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Eight patties from each formulation were thawed (15 h, 2 ºC ± 2) and manually
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wiped with a paper towel to remove visible exudates. The thawing loss (TL) was
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calculated as the weight difference between initial and thawed at storage time,
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expressed as a percentage of the initial weight. Four patties were wrapped in aluminium
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foil and cooked for 10 min in a forced air oven (Rational CM6, Groβküchentechnik
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GmbH, Landsberg a. Lech) at 170 ºC to bring the temperature at the centre of the
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product up to 70 °C (López-López et al., 2010). These cooking conditions were
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previously standardized for temperature by inserting thermocouples connected to a
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temperature recorder (Yokohama Hokushin Electric YEW, Mod. 3087, Tokyo, Japan).
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The cooked patties were weighed again to measure the cooking loss (CL, %) by
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difference.
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2.3. Proximate composition and energy content
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Proximate analyses were carried out on raw and cooked formulated patties in
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triplicate. Moisture and ash content (AOAC, 2000) and protein content ( LECO FP-
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2000 Nitrogen Determinator, Leco Corporation, St Joseph, MI, USA) were evaluated.
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Fat content was determined by a modified procedure of Bligh and Dyer (1959) (Hanson
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& Olley, 1963). Energy content (kcal) was calculated based on 9 kcal/g for fat and 4
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kcal/g for protein, and 2 kcal/g for dietary fibre (RD 930/1992; RD 1669/2009).
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2.4. Fatty acid profile
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The lipid extracts of the raw and cooked formulated patties were analysed by gas
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chromatography to determine fatty acid content. The method of Morrison and Smith
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(1964) was used to obtain the fatty acid methyl esters (FAMEs), using 14% boric
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trifluoride in methanol. Chromatographic analysis of FAMEs was performed using a
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Perkin–Elmer gas chromatograph (Perkin–Elmer, USA) equipped with a split-splitless
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injector and a flame ionization detector (FID), using a fused silica capillary column
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(0.32 mm internal diameter and 30 m long). The mobile phase consisted of helium C-50
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at a flow of 9 psig. Fatty acids were identified using Sigma reference standards.
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Quantification was done as reported López-López et al., 2009b.
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In order to evaluate the risk of atherosclerosis and/or thrombogenesis, we
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calculated the atherogenic index (AI) and thrombogenic index (TI), on the basis of the
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fatty acid results as a ratio between some saturated and unsaturated fatty acids,
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according to Ulbricht and Southgate (1991):
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AI = (C12:0 + 4 x C14:0 + C16:0)/( MUFA + n-3 PUFA + n-6 PUFA);
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TI = (C14:0 + C16:0 + C18:0) / (0.5 x MUFA + 0.5 x n-6 PUFA + 3 x n-3 PUFA + n-3
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PUFA/n-6 PUFA).
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2.5. Nutrient retentions
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Retention factors for various components were calculated according to Murphy,
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Criner and Gray (1975) as follows: Retention (%) = (g of cooked product x g of
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component in cooked product)/ (g of raw product x g component in raw product) x 100.
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2.6. Statistical analysis
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Data were analysed using Statgraphics Plus 5.1 (STSC Inc. Rockville, MD,
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USA). The experimental design used was the generalized linear model (GLM) for one-
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way and two-way ANOVA. Least squares differences were used for comparison of
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mean values among treatments and the Tukey HSD test to identify significant
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differences (P < 0.05) among formulation and cooking. The experiment was replicated
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twice.
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3. Results and discussion
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3.1. Thawing and cooking losses
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Thawing and cooking resulted in a systematic and significant loss of matter, affected (P
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< 0.005) by formulation. Since the amount of beef (source of salt soluble protein-SSP)
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used was similar in all the formulations (82.4-83.3%) and the salt (0.5%) was constant
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(Table 1), the concentration of SSP should be relatively similar in the formulated
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patties. Thus, differences in fat and water binding are more likely to be due to other
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components in the formulation such as the Wakame in combination with the olive oil
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emulsion rather than to SSP. Thawing loss (TL) and Cooking loss (CL) values ranged
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between 1.92-3.28 % and 27.61-34.34 % respectively in C, PE and TE samples (Table
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2), giving total weight losses (TL+CL) of between 29.52 and 37.58%. Hur et al. (2008)
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reported cooking loss values around 27 % in pork patties formulated with 5 % of pork
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backfat and of 5 % olive oil. These physicochemical properties of the beef patties were
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associated with the low salt concentrations (low ionic strength) used in this experiment
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(0.5 %), which resulted in low salt-soluble protein concentrations and limited the fat and
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water binding properties of the meat matrix. Weight loss during cooking of ground
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products varies widely depending on product formulation (e.g. salt content, protein
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level) and processing conditions, but the values recorded in this experiment are within
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the normal range given for comparable ground meat products (Chae, Keeton and Smith,
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2004; Turhan, Sagir & Ustun, 2005). Reformulated patties with added seaweed (W,
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WPE, WTE samples) presented lower (P < 0.05) thawing loss than seaweed-free patties,
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with total weight losses between 11.20 and 22.05 % (Table 2). The order of cooking
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loss was C>PE>TE>W>WTE>WPE. In all cases both cooking losses and total weight
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losses were smaller (P<0.05) in samples with Wakame and greater in samples without
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Wakame. The lowest CL and TL were recorded in patties containing a combination of
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emulsion and Wakame (Table 2). The improvement in binding properties may be
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related to the main seaweed components, i.e. dietary fibre and minerals (López-López et
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al., 2010). Partial or total replacement of pork backfat by olive oil-in-water emulsion
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had no effect (P > 0.05) on TL but resulted in lower (P<0.05) CL values in patties both
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with and without seaweed (Table 2). In this case the improvement in water and fat
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binding properties could be due to the stabilizing effect of the oil in the emulsion
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(López-López et al., 2010).
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3.2. Proximate composition
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The proximate composition of raw and cooked formulated patties is shown in
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Table 3. Composition was affected by formulation and cooking, with interaction
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between the two factors (P < 0.001). Proximate composition of raw samples was
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consistent with formulation conditions (López-López et al., 2010). Generally, samples
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with Wakame presented lower (P < 0.05) moisture contents and higher (P < 0.05) ash
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contents than free-seaweed samples. Fat proportions ranged between 8.22-10.95%,
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close to the target level; samples in which pork backfat was entirely replaced by oil-in-
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water emulsion (TE and WTE) had the lowest (P < 0.05) fat content (Table 3). The
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protein percentage was close to the target level and increased (P < 0.05) in samples
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containing oil-in-water emulsions (with soy protein as an emulsion stabilizer). Protein
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contents were similar (P>0.05) in C and W samples, indicating that Wakame addition
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contributed little to it.
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Irrespective of the formulation, moisture content decreased (P < 0.05) after
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thawing/cooking; the moisture retention values were lower in patties without seaweed
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(Table 3). These effects are consistent with the higher cooking and thawing losses found
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in free seaweed patties (Table 2). As reported previously, this behaviour was attributed
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to the technological properties of the main components of Wakame seaweed (dietary
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fibre and minerals), which can serve to overcome problems with water binding
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properties of low-salt meat products (Cofrades et al., 2008; López-López et al., 2010).
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While thawing/cooking has no observable effect (P > 0.05) on the percentage of
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fat in samples formulated with only animal fat (C and W), in all the other samples the
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fat content increased (P < 0.05) after cooking (Table 3). Fat retention in samples
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containing animal fat (C and W) was 61 and 73 % respectively. Fat retention values
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were higher (P < 0.05) (~100 %) in samples where the pork backfat was replaced
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(partially or entirely) by oil-in-water emulsion or a combination of oil-in-water
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emulsion and Wakame (Table 3), indicating that there was no noticeable fat loss during
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thawing/cooking in those samples. These results suggest that the prior oil stabilization
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process (emulsification) probably helps to retain the fat and reduce fat loss during
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cooking (López-López et al., 2010). Hur et al. (2008) reported fat retention values
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between 84-86 % in pork patties (15-17% fat content) formulated with 5 % pork backfat
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and 5 % olive oil (added in liquid form). Fat retention depends on different factors,
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among them the fat level (Sheard et al., 1998). It appears that as the fat content
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increases, the mean free distance between fat cells decreases, raising the likelihood of
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fat coalescing and then leaking from the product. Thus, high-fat products tend to lose
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large amounts of fat during cooking whilst low-fat products lose relatively little fat
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(Serrano et al., 2007; Sheard et al., 1998). Since the fat content of meat products is an
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important factor in food choice, the level of fat loss could be of interest to health-
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conscious consumers. After cooking, all the patties formulated in this experiment had a
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lower fat content (<12.8 g/100g) than those generally reported in normal-fat raw (18 –
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29%) and cooked (15 – 23%) beef burger (Moreiras, Carbajal, Cabrera, & Cuadrado,
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2003; Sheard et al., 1998).
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Weight losses (thawing/cooking) increased (P < 0.05) the protein percentage in
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formulated patties (Table 3), and the differences found in cooked samples were
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consistent with the cooking losses (Table 2) (López-López et al., 2010). However,
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because protein is not susceptible to migration, due to coagulation/denaturation protein
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retention levels stood at around 100 % (Table 3), similar to the levels reported in
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different meat products subjected to various cooking techniques (Maransesi,
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Bochicchio, Montellato, Zaghini, Pagliuca, & Badiani, 2005; Serrano et al., 2007).
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Thawing/cooking increased (P < 0.05) the ash percentage in patties with
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seaweed added (W, WPE and WTE) but had no effect (P > 0.05) in the other samples
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(Table 3). These results were due to differences in ash retention (Table 3); while ash
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retention levels of 59-69 % were found in samples without seaweed added (C, PE and
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TE), higher values (88-104 %) were observed in patties with seaweed added (W, WPE
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and WTE). Ash retention values of 72-98 % have been reported in cooked meats (Dal
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Bosco, Castellini, & Bernardini, 2001; Maransesi et al., 2005). Sheard et al. (1998)
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reported that the retention of ash ranged 98-127 % in grilled restructured steaks but
287
from 66 to 78% in conventional oven cooked samples. Dripping and leaching losses of
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minerals have an important effect on ash retention of cooked meat (Maranasi et al.,
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2005). There are two factors that can account for the higher ash retention observed in
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this experiment in products containing seaweed. One is the low cooking loss in seaweed
291
patties, an effect that has been attributed to the improved water binding properties of the
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Wakame components (López-López et al., 2010). The other is that the minerals supplied
293
by the seaweed are strongly bonded to anionic polysaccharides (e.g. alginate) in the
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seaweed (Mabeau & Fleurence, 1993) and hence less susceptible to loss. Pork backfat
295
substitution by olive oil in water emulsion, also produced an increase (P < 0.05) in ash
296
retention (Table 3) due to the lower CL in those samples, attributed to the prior
297
stabilization process.
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These results indicate that during thawing/cooking the highest losses are of
299
moisture, ash and fat in the case of seaweed-free samples, while in samples with added
300
Wakame/olive oil, mostly moisture is lost, with no significant loss of fat, protein or ash
301
(Tables 3 and 4). Hence, the seaweed and the oil emulsion help to retain the food’s
302
components in the course of heating, thus promoting availability.
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3.3. Energy content
305
Energy values were affected by formulation and cooking, with a significant
306
interaction (P < 0.001) between both factors. The energy contents of the raw formulated
307
beef patties were lower than 168 kcal/100 g (Table 4), values that are generally found in
308
low and reduced fat ground products (Bilek & Turhan, 2009; Sheard et al., 1998). After
309
cooking, the energy content of all formulated patties increased (P < 0.05) in a range
310
from 177.59 to 228.74 kcal/100 g (Table 4). However, the pattern changes when energy
311
values are based on the initial 100 g of raw products (Table 4).
312
In raw samples the fat accounted for between 50-59 % of the total caloric
313
content, while in cooked samples this proportion varied between 43-52 % (Table 4).
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314
After cooking, the contribution of fat to total energy was generally higher in samples in
315
which animal fat was replaced by olive oil-in-water emulsion (Table 4). This pattern is
316
consistent with the results of moisture and fat retention (Table 3).
317
Depending on the formulation (Table 1), when backfat was replaced partially
318
(PE and WPE samples) or totally (TE and WTE samples) by olive oil-in-water
319
emulsion, around 24 and 48 kcal/100 g (close to 10 and 20% of total energy)
320
respectively was supplied by the olive oil. Minor changes in these proportions may be
321
expected after cooking, considering the high rate of fat retention in samples formulated
322
with olive-oil emulsion (Table 3), and the generally slight changes in the contribution of
323
fat to product energy values (Table 4). After cooking, the samples with the lowest
324
energy content were the ones containing Wakame (Table 4). The contribution of
325
specific fatty acids to total product energy is discussed in the next section.
326
327
3.4. Fatty acid content
328
The fatty acid content of formulated patties, shown in Tables 5 and 6, was
329
affected by formulation and cooking, with interaction between both factors (P < 0.001).
330
Raw formulated patties presented high concentrations of SFAs and MUFAs,
331
representing around 46% of total fatty acids (data not shown), with a lower PUFAs
332
concentration (Table 6). In this sample (C) the SFAs with the highest concentration
333
were palmitic and estearic acid, while the most abundant was oleic acid, with a
334
concentration of 4.3 g/100 g (Table 5). MUFAs and PUFAs together accounted for
335
54 % of the total fatty acids (data not shown). Of PUFAs, linoleic acid was the most
336
abundant (0.64 g/100 g of product). These results are consistent with the fatty acid
337
profile reported elsewhere in ground beef products (Chae et al., 2004; Georgantelis,
338
Blekas, Katikou, Ambrosiadis, & Fletouris, 2007; Libreloto et al., 2008).
14
339
The main differences found in fatty acid concentrations in the reformulated raw
340
patties were due to the replacement of animal fat by oil-in-water emulsion, since
341
Wakame incorporation produced no appreciable changes (Tables 5 and 6) given its low
342
lipid content (< 1%) (Cofrades et al., 2008). Compared with the control sample (C), the
343
products formulated with olive oil contained less (P < 0.05) SFAs. This difference
344
augmented with the proportion of pork backfat replaced by the olive oil (Tables 5 and
345
6). As compared with all animal fat samples (C and W), in general, the replacement of
346
pork backfat increased the concentration of MUFAs and oleic acid in patties. While the
347
proportion of MUFAs and oleic acid was around 46 and 42% of total fatty acids
348
respectively in C and W samples (data not shown), the proportions were 51-52 and 47-
349
48% for partial replacement (PE and WPE samples) and 57 and 53 % for total pork
350
backfat replacement (TE and WTE). Due to differences in the fat content of formulated
351
patties (Table 2), this pattern is less evident when changes in fatty acid composition are
352
expressed per 100 g of product (Tables 5 and 6). Patties in which pork backfat was
353
totally replaced by olive oil-in-water-emulsion (TE and WTE patties) had the lowest (P
354
< 0.05) linoleic acid, total PUFAs and n-6 PUFAs contents in raw samples, while
355
formulation had no observable effect on n-3 PUFAs contents (Tables 5 and 6). The fatty
356
acid compositions of formulated patties were consistent with formulation conditions and
357
with the composition of the olive oil. Since oil-in-water emulsion contains 52.6% olive
358
oil, the oil proportion were 2.6 % in PE and WPE samples (around 25 % of product fat
359
contents) and 5.2 % in TE and WTE samples (over 60 % of product fat contents). The
360
lipid content in the PE sample came from the lean beef meat, pork backfat and olive oil,
361
whereas in TE it came only from the beef meat and olive oil. Hur et al. (2008) reported
362
the addition of olive oil (5% in liquid form) to pork patties where olive oil levels
363
reached around 30 % of product’s fat content, which is a lower proportion than in the
15
364
present experiment (around 60%). These authors reported that olive oil substitution
365
increased oleic and linoleic acids and MUFAs and reduced SFAs percentages (with
366
respect to total fatty acid) as compared with all animal fat pork patties. Other studies
367
reporting the addition of olive oil in meat products such as cooked sausages (Bloukas &
368
Paneras, 1993; López-López et al., 2009a,b; Pappa, Bloukas, & Arvanitoyannis, 2000)
369
and fermented sausages (Muguerza, et al., 2001; Bloukas, Paneras, & Fournitzis, 1997;
370
Bloukas et al., 1997) have also indicated that the replacement of pork backfat by olive
371
oil originated a healthier lipid composition since the proportion of MUFAs (mainly
372
oleic acid) increased (Jiménez-Colmenero, 2007).
373
The thermal treatment affected the fatty acid concentrations in the formulated
374
patties in different ways (Tables 5 and 6). In general, cooking maintained (P > 0.05) or
375
reduced (P < 0.05) the concentration of fatty acids in C and W patties and increased
376
them (P < 0.05) in samples with olive oil-in-water emulsion added (PE, WPE, TE and
377
WTE). This difference in behaviour is due mainly to weight loss during cooking and to
378
changes in fat retention (Table 3). Increases in fatty acid concentrations as a result of
379
cooking have been reported in trimmed beef muscles and in restructured beef steaks
380
(Badiani et al., 2002; Librelotto et al., 2008). Total animal fat replacement reduced (P <
381
0.05) the SFAs content of cooked beef patties, and increased (P<0.05) MUFAs content,
382
with oleic acid reaching 5.6-6.6 g/100 g product (Tables 5 and 6). These oleic acid
383
levels are higher than in burgers with normal (more caloric) fat content (5.20 g/100 g)
384
(Moreiras et al., 2003) or in restructured beef steak with comparable fat content, where
385
they do not exceed 3.6 g/100g (Librelotto et al., 2008). It is important to note that
386
linoleic and linolenic acid contents increased during cooking in samples with olive oil
387
emulsion, resulting in products with higher concentrations than reported in other ground
388
beef products (Librelotto et al., 2008; Moreiras et al., 2003). Additionally, the
16
389
concentrations of other kinds of fatty acids, like conjugated linoleic, eicosapentaenoic,
390
eicosapentaenoic and docosapentaenoic acids, were not affected (P > 0.05) by cooking
391
(Table 5).
392
The contribution of specific fatty acids to total product energy in raw and cooked
393
formulated patties is reported in Table 6. As compared with control sample (C),
394
replacement of pork backfat by oil-in-water emulsions caused a reduction (P < 0.05) in
395
energy value from SFAs in raw patties, while MUFAs and PUFAs proportions varied
396
with product formulation. As a result of the changes in individual fatty acid (Tabla 5)
397
and fat retention (Table 3), cooking produced an increase (P < 0.05) in energy value
398
from SFAs, MUFAs and PUFAs only in samples with olive oil emulsion (Table 6).
399
The PUFA/SFA ratio is one of the main parameters used to assess the nutritional
400
quality of the lipid fraction in foods. The recommended healthy PUFA/SFA ratio is
401
above 0.4 (Wood, Richardson, Nute, Fisher, Campo, & Kasapidou, 2003). In the present
402
study this ratio for raw patties ranged between 0.16 and 0.20 (Table 7), which is within
403
the ranges reported for beef patties (all beef fat, 0.05) (Bilek & Turhan, 2009) and for
404
meat emulsion systems (all pork fat, 0.29) (López-López et al., 2009c). A PUFA/SFA
405
ratio of approximately 0.10 has been reported for beef meat (Badiani et al., 2002; Enser,
406
2000). As compared with C sample, Wakame and olive oil emulsion in seaweed-free
407
patties increased (P < 0.05) the PUFA/SFA ratio. The PUFA/SFA ratio has been
408
reported to increase in pork patties made by substituting olive oil for backfat (Hur et al.,
409
2008). Although there was no apparent behaviour pattern attributable to the formulation,
410
this ratio increased significantly in some formulations (PE, W and WTE) during
411
cooking (Table 7). Similarly, an increase in the polyunsaturated to saturated fatty acid
412
ratio for cooked compared to raw samples has been reported (Gerber, Scheeder, &
413
Wenk, 2009). These authors indicated that unsaturated fatty acids, especially PUFAs,
17
414
are less affected by cooking since they are part of the membrane structure. Thus, the
415
proportional change in fatty acid composition may be explained by loss of lipid
416
containing mainly triacylglycerols of adipose tissues with relatively more saturated than
417
unsaturated fatty acids. On the other hand, no changes were observed in this ratio in
418
beef muscle as affected by various cooking methods (boiling, broiling, oven roasting
419
and microwaving) (Badiani et al., 2002).
420
There is abundant evidence associating a higher n-6/n-3 ratio with the promotion
421
of pathogenesis of many diseases, including CVD, cancer, etc., and lower ratios with a
422
suppressive effect (Simopoulos, 2002). Therefore, the dietary recommendation is to
423
reduce this value to less than 4 for prevention of CVD. The ratios found in the present
424
experiment (Table 7) diverged to some extent from the recommended values due to the
425
combination of lipid materials (from beef, backfat, Wakame and olive oil). The n-6/n-3
426
ratios from animal fat were similar than those founded in the present study (Jiménez-
427
Colmenero, & Toldrá, 2006; Mourot, 2009; Okuyama and Ikemoto, 1999). The n-6/n-3
428
ratio in patties where olive oil totally replaced backfat (TE and WTE) was lower (P <
429
0.05) than in control sample (Table 7). This effect would appear to be due mainly to a
430
reduction of n-6 PUFAs, since the n-3 PUFAs content was similar (P > 0.05) in all
431
patties (Table 6). Wakame incorporation and partial animal fat substitution generally
432
produced only a minor effect (Table 7). Cooking did not affect this ratio in any of the
433
samples (Table 7). Badiani et al. (2002) likewise reported no changes in this ratio in
434
beef muscle as affected by various cooking methods.
435
The effect of each fatty acid on human health is not fully expressed by the ratios
436
mentioned above, since they consider each class of fatty acids, but not the individual
437
fatty acid. AI and the TI were devised to do this (Ulbricht & Southgate, 1991). The AI
438
assesses the risk of atherosclerosis and the TI is an indication of the potential
18
439
aggregation of blood platelets, so very low values of AI and TI are recommended for a
440
healthy diet. The AI and TI are shown in Table 7. Olive oil-free patties (C and W)
441
presented AI around 0.7 and TI around 1.6. Seaweed addition did not affect (P > 0.05)
442
these parameters, as reported by López-López et al. (2009c) in meat emulsion systems
443
with 5 % Wakame. However both indexes were lower (P < 0.05) in samples where pork
444
backfat was partially or totally replaced by olive oil emulsion. Similar results have been
445
reported in pork frankfurters formulated with olive oil (López-López et al., 2009b).
446
Cooking reduced (P < 0.05) AI in PE and WTE samples and TI in PE, WPE and WTE
447
patties (Table 7).
448
449
3.5. Fatty acid retention
450
Fatty acid retention (Table 8) was affected by formulation (P < 0.05). Generally,
451
fatty acid retention of reformulated products was better than in C sample in those
452
samples where pork backfat was entirely replaced by oil-in-water emulsion (TE and
453
WTE) or when backfat was partially replaced but seaweed was also included in the
454
formulation (WPE) (Table 8). As reported in the fat retention analysis, there was
455
noticeable fatty acid loss in these samples during thawing/cooking. These effects have
456
been associated with the conditions in which the olive oil is added (stabilized as an oil-
457
in-water emulsion) and the technological contribution of some seaweed components
458
such as dietary fibre and minerals (López-López et al., 2010).
459
460
Conclusion
461
The composition of healthier low-salt, low-fat beef patties with added Wakame
462
seaweed and partial or total replacement of pork backfat with olive oil-in-water
463
emulsion was affected by formulation and cooking. Cooking caused a systematic and
19
464
significant loss of matter; the highest losses were of moisture, ash and fat in the case of
465
seaweed-free samples, while in samples with added Wakame/olive oil, mostly moisture
466
was lost, with no significant loss of fat, protein or ash. Fat loss significantly affected the
467
fat and fatty acid contents and the energy values of products, although the extent varied
468
with product formulation. The fat binding properties of these meat matrixes improved
469
when animal fat was replaced by olive oil-in-water emulsion. Cooking would thus
470
appear to affect the amount as well as the proportion of the fatty acids to some extent,
471
which should be taken into account in calculations of fat (fatty acid) consumption and
472
energy intakes. These factors need to be considered in the case of meat products, and
473
specifically healthier lipid formulations, given the relatively large losses of fat that can
474
often occur during cooking. In the experimental conditions, the reformulation process
475
(animal fat replaced by olive-in-water emulsion and/or addition of Wakame) resulted in
476
a healthier lipid (low-fat with olive oil added) beef patty.
477
478
Acnowledgements
479
This research was supported under projects AGL2005-07204-CO2-02, Plan Nacional
480
de Investigación Científica, Desarrollo e Innovación Tecnológica (I+D+I) and
481
Consolider-Ingenio 2010: CARNISENUSA (CSD2007-00016). The authors wish to
482
thank the Spanish Ministerio de Innovación y Ciencia for Ms. López-López’s
483
predoctoral fellowship. Thanks are due to Algamar S.A. for supplying the seaweed.
484
485
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