emulsion meat systems

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MEAT SCIENCE Meat Science 79 (2008) 767–776 www.elsevier.com/locate/meatsci

Influence of different types and proportions of added edible seaweeds on characteristics of low-salt gel/emulsion meat systems S. Cofrades a,*, I. Lo´pez-Lo´pez a, M.T. Solas b, L. Bravo c, F. Jime´nez-Colmenero a a

Departamento de Ciencia y Tecnologı´a de Carne y Productos Ca´rnicos y del Pescado y Productos de la Pesca, Instituto del Frı´o (CSIC), C/ Jose Antonio Novais, 10, 28040 Madrid, Spain b Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain c Departamento de Metabolismo y Nutricio´n. Instituto del Frı´o (CSIC), C/ Jose Antonio Novais, 10, 28040 Madrid, Spain Received 27 June 2007; received in revised form 8 October 2007; accepted 18 November 2007

Abstract The effects of three different types of edible seaweeds, Sea Spaghetti (Himanthalia elongata), Wakame (Undaria pinnatifida), and Nori (Porphyra umbilicalis) added at two concentrations (2.5% and 5% dry matter) on the physicochemical and morphological characteristics of gel/emulsion systems were evaluated. The addition of seaweeds improved (P < 0.05) water- and fat-binding properties except in the case of Nori added at 2.5%. Hardness and chewiness of the cooked products with added seaweed were higher (P < 0.05), and springiness and cohesiveness were lower (P < 0.05) than in control samples. Colour changes in meat systems were affected by the type of seaweed. The morphology of sample differed depending on the type of seaweed added, and this is the result of differences in physical and chemical characteristic of the seaweed powder used. In general, products formulated with the brown seaweeds (Sea Spaghetti and Wakame) exhibited similar behaviour, different from that of products made with the red seaweed Nori. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Gel/emulsions meat systems; Seaweeds; Dietary fibre; Binding properties; Texture

1. Introduction Thanks to advances in our understanding of the relationship between diet and health, consumers are increasingly more interested in foods that not only adequately meet nutritional needs but also confer health benefits, hence the growing demand for ‘‘functional foods”. Meat and meat products are generally recognized as contributing to nutrition in that they constitute an important source of high biological value proteins, group B vitamins, minerals, trace elements and other bioactive compounds. Regrettably, a negative image often attaches to meat products as a source of fat, saturated fatty acids, cholesterol, sodium

*

Corresponding author. Tel.: +34 91 549 23 00; fax: +34 91 549 36 27. E-mail address: [email protected] (S. Cofrades).

0309-1740/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2007.11.010

and other substances which in inappropriate amounts may produce negative physiological effects. Numerous researchers are working to optimize meat product composition in order to achieve a composition that is better suited to nutrient intake goals. There are various possible strategies for developing healthier meats and meat products, including functional foods. One of the most important of these strategies is to design foods that will reduce the concentration of some unhealthy compounds (fat or sodium) and promote the presence of healthy compounds (Anandh, Lakshmanan, Mendiratta, Anjaneyulu, & Bisht, 2005; Arihara, 2006; Ferna´ndez-Gine´s, Fern´ lvarez, 2005; a´ndez-Lo´pez, Sayas-Barbera, & Pe´rez-A Jime´nez-Colmenero, Carballo, & Cofrades, 2001; Jime´nez-Colmenero, Reig, & Toldra´, 2006; Muguerza, Ansorena, & Astiasara´n, 2004). To achieve this, various non-meat ingredients have been used in the formulation of meat-based functional foods. Meat, as one of the most

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important commonly-consumed foods, offers excellent ways to promote intake of functional ingredients without any radical changes in eating habits. Seaweeds have been used as food since ancient times. They are widely consumed in Asian countries, and to a lesser extent also in Europe and America. Seaweeds contain various bioactive compounds with potential healthbeneficial properties and are therefore suitable for use as ingredients in the formulation of healthier foods. The chemical composition of seaweeds varies with species, habitat, maturity and environmental conditions (Hou & Yan, 1998). Edible seaweeds contain good quality protein and large amounts of vitamins (Fleurence, 1999; Kolb, Vallorani, Milanovic, & Stocchi, 2004). The lipid content of seaweed is 1–3% dry matter. However, algal lipids have a higher proportion of essential unsaturated fatty acids, particularly long chain omega-3 polyunsaturated fatty acids (PUFAs) like eicosapentaenoic acid (EPA, C20:5n-3) (Fleurence, Gutbier, Mabeau, & Leray, 1994; Sa´nchezMachado, Lo´pez-Cervantes, Lo´pez-Hernandez, & Paseiro-Losada, 2004). Long chain n-3 PUFAs such as docosahexanoic acid (DHA, 22:6n-3), reduce the risk of atherosclerosis, coronary heart disease, inflammatory disease and may even favourably affect behavioural disorders (Connor, 2000). Algae are an excellent source of minerals, mainly Ca, Na, Mg, P, K, I, Fe and Zn, thanks to their capacity to absorb inorganic substances from the surrounding marine media and store them in their tissues (Davis et al., 2003; Munilla, Go´mez-Pinilla, Ro´denas, & Larrea, 1995; Rupe´rez, 2002). They are the best natural source of iodine, and thus algae consumption could help to meet daily requirements of iodine in the diet (Kolb et al., 2004). It is also important to note that seaweeds contain bioactive compounds with known antioxidant properties, such as polyphenols, carotenoids and tocopherols, which play an important role in protecting the body’s cells and molecules from oxidative stress (Jime´nez-Escrig, Jime´nez-Jime´nez, Pulido, & Saura-Calixto, 2001; Sa´nchezMachado, Lo´pez-Hernandez, & Paseiro-Losada, 2002) and cancer chemoprevention properties (Kim et al., 1998; Okuzumi et al., 1990). Seaweeds are considered a good source of dietary fibre (DF), since their main components are non-digestible polysaccharides. Seaweed DF differs from that of land plants in composition, chemical structure, physicochemical properties and biological effects (Lahaye & Kaeffer, 1997; Rupe´rez & Saura-Calixto, 2001). Seaweed DF has several beneficial physiological effects on humans, important among them being hypocholesterolaemic and antihypertensive effects (Jime´nez-Escrig & Sa´nchez-Muniz, 2000) and antioxidant protection (Kuda, Tsunekawa, Hishi, & Araki, 2005). An increase in the level of dietary fibre in the daily diet has therefore been recommended (Backers & Noll, 1998). In addition to the role of some of the components which have potential benefits for the human body, some technological advantages can be derived from the use of marine algae as ingredients in meat products. This is basically

thanks to their composition, especially the physicochemical properties of their dietary fibre. On the technological side, fibres are used as texturing and bulking agents, particularly in the making of low calorie foods. These properties depend chiefly on the capacity of the fibres to absorb and retain water (Rupe´rez & Saura-Calixto, 2001). Dietary fibres from different sources have been studied alone or in combination with other ingredients for the formulation of different meat products (ground/restructured products and meat emulsions) with a view to increasing cooking yields thanks to their water- and fat-binding properties, improving texture and reducing formulation costs (Cofrades, Guerra, Carballo, Ferna´ndez-Martı´n, & Jime´nezColmenero, 2000; Ferna´ndez-Gine´s, Ferna´ndez-Lo´pez, ´ lvarez, 2004; Jime´nezSayas-Barbera, Sendra, & Pe´rez-A Colmenero, Ayo, & Carballo, 2005; Selgas, Ca´ceres, & Garcı´a, 2005; Thebaudin, Lefebvre, Harrington, & Bourgeois, 1997). At the same time, the high concentration of mineral elements in seaweeds suggests the possibility of using them to reduce the amount of added NaCl in meat processing. Since sodium intake generally exceeds nutritional recommendations in industrialized countries and approximately 20–30% of common salt intake comes from meat products (Wirth, 1991), there is increasing interest among consumers and processors in reducing the use of salt (minimizing sodium) in meat processing. The seaweeds of interest collected on the northwest Iberian coast include the red seaweed Nori (Porphyra umbilicalis) and the brown seaweeds Wakame (Undaria pinnatifida) and Sea Spaghetti (Himantalia elongata), whose composition is different (Gudiel-Urbano & Gon˜i, 2002; Nishide, Anzai, Uchida, & Nisizawa, 1990). As a result of this diversity (basically in polysaccharide components), there are differences in physicochemical, rheological, structural and chemical properties as well as biological properties (Gudiel-Urbano & Gon˜i, 2002; Lahaye, 1991; Lahaye & Kaeffer, 1997). Today seaweeds provide the raw material for industrial production of some purified ingredients (agar, carrageenan, alginates or oils) used in various kinds of food processing, but very little attention has been paid to the use of edible seaweeds as ingredients; at present they are used in snacks or cheese (Lalic & Berkovic, 2005; Mamatha, Namitha, Senthil, Smitha, & Ravishankar, 2007). In meat products, Soon-Sil, Jeong-Ro, Jong-Cheol, Jae-Soo, and Chang-Bum (1999), have studied the addition of 1–5% powdered Sagassum thunbergii or Gelidium amansii to hamburgers. The use of seaweeds as food ingredients is thus of indubitable interest from the standpoints of nutrition and technology. The development of functional foods opens up new possibilities for the use of seaweeds (Fleurence, 1999), one of which is the opportunity for the meat industry to improve its ‘‘image” and address consumer demands. As with other non-meat ingredients containing functional components also used in meat processing, the first requirement is to evaluate the consequences of their addition for the characteristics of meat system. In light of the foregoing,

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the object of this research was to determine how the addition of three different types of seaweed (Wakame, Nori and Sea Spaghetti) at two different concentrations (2.5% and 5%) influences the physicochemical properties (texture, water- and fat-binding properties, colour) and microstructure of meat gel/emulsion systems formulated with low levels of added salt (0.5% NaCl). 2. Materials and methods 2.1. Preparation of meat, seaweeds and additives Post-rigor pork meat (mixture of different muscles: biceps femoris, semimembranosus, semitendinosus, gracilis and aductor) and fresh pork backfat were obtained from a local meat market. The meat was trimmed of visible fat and connective tissue. Meat and backfat were passed through a grinder with a 0.6 cm plate (Mainca, Granollers, Spain). Lots of approx. 500 g were vacuum packed, frozen and stored at 20 °C until used. The seaweeds (Undaria pinnatifida, Himantalia elongata and Porphyra umbilicalis) were supplied by Algamar C.B., (Redondela, Pontevedra, Spain). Fresh marine seaweeds were collected on the Atlantic coast, dried in the shade and packed in polyethylene plastic bags for commercial distribution by the processers. These seaweeds were ground (at the Instituto del Frı´o) in a mill (ZM 200, Retsch GmbH and Co. KG, Haan, Germany), passed through a screen with an aperture of 0.25 mm and stored in plastic flasks at 4 ± 2 °C until used. Additives used for preparation of gel/emulsion systems included sodium chloride (Panreac Quı´mica, S.A. Barcelona, Spain), sodium tripolyphosphate (STP) (Manuel Riesgo, S.A. Madrid, Spain) and sodium nitrite (Fulka Chemie GmbH, Buchs, Germany). 2.2. Preparation of gel/emulsion systems Meat and backfat packages were thawed (approx. 18 h at 3 ± 2 °C up to between 1 and 2 °C). Seven different products were prepared with a target final protein level of 13% (meat protein) and a total fat content of 10%. Two different levels (2.5% and 5% dry matter) of the three seaweeds were added to replace an equal proportion of

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water (Table 1). The procedure was as follows: raw meat material was homogenized and ground for 1 min in a chilled cutter (2 °C) (Stephan Universal Machine UM5, Stephan u. So´hne GmbH and Co., Hameln, Germany). All the fat and half the seaweeds, NaCl (2.0% for control samples and 0.5% for samples with seaweeds added), and STP and sodium nitrite (the last two previously dissolved in the added water) were added to the ground meat and mixed again for 1 min, then the rest of the ingredients were added and homogenized for 1 min. Finally the whole meat batter was homogenized under vacuum conditions for 2 min. Mixing time was standardized at 5 min and the final batter temperature was below 12 °C in all cases. The batters were stuffed into plastic tubes (diameter 3.5 cm) and centrifuged (2500g, 3 °C, 15 min) (Multifuge 3L-R, Kendro Laboratory Products GmbH, Hanau, Germany) to homogenize them and eliminate any air bubbles. Finally the tubes with the samples were hermetically closed and heated in a waterbath during 30 min at 70 °C. 2.3. Proximate analysis and pH Analyses were performed on the raw material (meat, backfat and seaweeds) and the cooked meat batters. Moisture and ash contents of the raw materials and batters were determined (AOAC, 2000) in triplicate. Protein content was measured in triplicate with a LECO FP-2000 Nitrogen Determinator (Leco Corporation, St Joseph, MI, USA). Fat content of meat and cooked samples was evaluated (in duplicate) according to Bligh and Dyer (1959). Fat content of the seaweed was determined (in triplicate) by the method of Sa´nchez-Machado et al. (2004). Total, soluble and insoluble dietary fibre contents of seaweeds were analysed according to Saura-Calixto, Garcı´a-Alonso, Gon˜i, and Bravo (2000). The pH of the cooked samples was determined six times using an Orion Research 720A pH meter (Instrumentacio´n Analı´tica, S.A. Madrid, Spain) on a homogenate of 10 g of sample in 100 mL distilled water. 2.4. Surface colour Eight samples from each system were evaluated for colour analysis using a Chroma Meter CR-400 (Konica

Table 1 Formulation (g) of gel/emulsion systemsa Sample

Meat

Backfat

Seaweed

NaCl

STP

Sodium nitrite

Water

Total

C W2.5 W5 N2.5 N5 S2.5 S5

355.6 355.6 355.6 355.6 355.6 355.6 355.6

48.8 48.8 48.8 48.8 48.8 48.8 48.8

0.0 16.8 33.6 16.8 33.7 16.8 33.7

12.0 3.0 3.0 3.0 3.0 3.0 3.0

1.8 1.8 1.8 1.8 1.8 1.8 1.8

0.09 0.09 0.09 0.09 0.09 0.09 0.09

181.6 173.8 156.9 173.7 156.9 173.7 156.9

600.0 600.0 600.0 600.0 600.0 600.0 600.0

a C, 0% added seaweed; W2.5, W5, 2.5% and 5% added Wakame respectively; N2.5 N5, 2.5% and 5% added Nori respectively; S2.5, S5, 2.5% and 5% added Sea Spaghetti respectively. STP, sodium tripolyphosphate.

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Minolta Business Technologies, Inc., Tokyo, Japan). CIE L* (lightness, black [0] to light [100]), a* (redness, red [60], to green [ 60]) and b* (yellowness, yellow [60] to blue [ 60]) values were measure to evaluate the colouring effects of seaweeds added. 2.5. Emulsion stability (Water- and fat-binding properties) After heating (previously described in the preparation of the gel/emulsion systems), the tubes containing the different samples were opened and left to stand upside down (for 50 min) to release the exudate onto a plate. Emulsion stability as total fluid released (TFR) was expressed as percentage of initial sample weight. Water released (WR) was determined as wt.% loss after heating the total fluid released for 16 h on a stove at 105 °C. Fat released (FR) was calculated as the difference between TFR and WL. Determinations were carried out six times.

increasing concentrations of acetone, critical-point-dried, sputter-coated with gold/palladium in a metallizer (Blazer, SCD004) and scanned by SEM (Jeol, JSC 6400, Tokyo, Japan) at 20 kV. A large number of micrographs were taken in order to select the most representative ones. 2.8. Statistical analysis Data were analysed using Statgraphics Plus 2.1 (STSC Inc. Rockville, MD, USA) for one-way ANOVA. Least squares differences were used for comparison of mean values among treatments and the Tukey HSD test to identify significant differences (P < 0.05) among types and concentrations of the seaweeds added. 3. Results and discussion 3.1. Seaweed composition, colour and microstructure

2.6. Texture profile analysis Texture Profile Analysis (TPA) was performed in a TAXT2 Texture Analyzer (Texture Technologies Corp., Scarsdale, NY) as described by Bourne (1978). Eight determinations per formulation of cooked samples (diameter 2.5 cm, height 3.0 cm) were compressed to 30% of their original height. Force–time deformation curves were derived with a 250 N load cell applied at a constant crosshead speed of 0.8 mm/s. Attributes were calculated as follows. Hardness (Hd): peak force (N) required for first compression; cohesiveness (Ch): ratio of active work done under the second compression curve to that done under the first compression curve (dimensionless); springiness (Sp): distance (mm) of sample recovery after the first compression; and chewiness (Cw): Hd  Ch  Sp (N  mm). Measurement of samples was carried out at room temperature. 2.7. Microstructure Microstructure was analysed by scanning electron microscopy (SEM). The seaweeds and the cooked samples were fixed with a mixture (1:1 v/v) of paraformaldehyde (4%) and glutaraldehyde (0.2%) in 0.1 M phosphate buffer pH 7.2, post-fixed with OsO4, washed, dehydrated in

Moisture was around 11% irrespective of the type of seaweed (P > 0.05). Ash content was high, 30% and 37%, in Sea Spaghetti and Wakame, respectively (Table 2); Nori presented the lowest (P < 0.05) ash content and the highest (P < 0.05) protein content (39%). All three seaweeds exhibited a particularly low fat content (0.3–1.3%). Total dietary fibre (TDF) of seaweeds ranged between 35% and 50%, with differences in the content of the soluble (SDF) and insoluble (IDF) dietary fibre fractions in all three seaweeds. Wakame had the highest IDF content, and Sea Spaghetti slightly less (Table 2). Fleury and Lahaye (1991) reported that the physicochemical properties of powdered seaweed could be assumed to reflect those of the fibre present. Also, seaweed proteins are closely associated with cell wall polysaccharides (Fleurence, LeCoeur, Mabeau, Maurice, & Landrein, 1995; Jordan & Vilter, 1991) and hence may also play a role in physicochemical properties of algae such as water-holding capacity. In this study, the total protein plus dietary fibre of seaweeds varied between 55% and 74% dry matter (Table 2); it is therefore possible that the physicochemical properties of the seaweeds are determined mainly by these two chemical components (Wong & Cheung, 2000). The protein, ash, fat and dietary fibre content of the three seaweeds studied were within the range reported by various authors for red and brown seaweeds (Mabeau

Table 2 Composition and color properties of the seaweeds* Per 100 g dry matter

Protein

Fat

Ash

SDF

IDF

TDF

L*

Sea Spaghetti Wakame Nori SEM

4.84a 11.93b 39.01c 0.23

1.32a 0.88ab 0.34b 0.15

30.09a 36.83b 11.72c 0.64

24.37a 12.53b 21.22c 0.55

25.94a 28.42b 14.24c 0.51

50.31a 40.95b 35.46c 0.70

67.57a 68.34b 27.58c 0.19

a* 0.03a 3.91b 4.28c 0.03

b* 19.06a 17.26b 0.47c 0.15

TDF = total dietary fibre content; IDF = insoluble dietary fibre content; SDF = soluble dietary fibre content. Means with different letters in the same column are significantly different (P < 0.05). SEM: standard error of the mean. * For sample denomination see Table 1.

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& Fleurence, 1993; Rupe´rez & Saura-Calixto, 2001; Sa´nchez-Machado et al., 2004). Colour parameters for the seaweeds studied are presented in Table 2. The two brown algae, Sea Spaghetti and Wakame, presented similar L* and b* values, although significantly different (P < 0.05), which were higher (P < 0.05) than in Nori. The same two seaweeds presented lower a* values, tending more towards green–brown and away from red (Table 2). On the contrary, Nori exhibited the highest (P < 0.05) a* value, with a purplish colour tending towards a blackish shade closer to red. Variations in colour parameters between seaweeds are the result of differences in contents of pigments such as chlorophyll, xanthophyll, phycophine, phycoerythrin and phycocyanin. Thus, brown seaweeds (Sea Spaghetti and Wakame) present similar colour attributes, quite different from those observed in red seaweed (Nori) (Table 2). In addition to chlorophyll, brown seaweeds contain phycophine, a brown pigment, and xanthophyll, a yellow pigment, which endows them with a greater variety of shades in the range yellow to dark chestnut by way of yellowish-greens and masking the green of the chlorophyll. The range of colourings from red to purplish or almost blackish in Nori (red seaweed) is a result of the combination of chlorophyll, phycoerythrin and phycocyanin (www.elergonomista.com/botanica/algas.htm; www.ilustrados.com/publicaciones/EpZyFuFElAOZavLTAo.php). Although all three types of seaweed were put through the same preparatory process (milling and screening), the dry powder of each one presented different structural characteristics (Fig. 1). These were evident from the different particle sizes. Sizes were similar in Nori and Sea Spaghetti while Wakame presented more structural disintegration. 3.2. Proximate analysis and pH of gel/emulsion systems Proximate analysis of the cooked gel/emulsion samples showed some significant differences between types of formulation (Table 3). Protein and fat contents of cooked meat batters were close to the target levels of 13% and 10%, respectively (Table 3). In general, the addition of 5% of any of the seaweeds reduced the moisture level in gel/emulsion systems as the seaweed replaced water (Table 3). Protein levels varied from 13.84% to 15.74%, reflecting differences in the protein contents of the seaweeds (Table 2). Thus, samples made with Nori presented higher (P < 0.05) protein content than control samples or those formulated with Sea Spaghetti or Wakame, in which protein content was similar (P > 0.05) (Table 3). No significant differences were observed in the fat content of the gel/emulsion samples irrespective of the formulation (Table 3). However, ash levels varied between 1.60% and 3.28% (Table 3); the larger the amount of added algae, the greater was the increment of ash in the gel/emulsion system. This effect was more pronounced when Wakame was used, which is consistent with its composition (Table 2).

Fig. 1. Scanning electro´n micrographs (50 magnification) of the three seaweeds. (a) Sea Spaghetti; (b) Wakame and (c) Nori.

In terms of seaweed composition (Table 2), addition of 5% Sea Spaghetti and Wakame, with higher TDF content than Nori, would add more dietary fibre to the meat preparation (2.52% and 2.05%, respectively) than Nori, which

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Table 3 Proximate ana´lisis (%) and pH of cooked gel/emulsion systems*

Table 4 Colour parameters of cooked samples*

Sample

Moisture

Protein

Fat

Ash

pH

Sample

Lightness L*

Control S2.5 S5 W2.5 W5 N2.5 N5 SEM

72.52a 72.71ac 70.65bd 73.44c 71.12bd 71.39b 70.22d 0.19

14.51a 13.95a 13.84a 14.02a 14.22a 15.39b 15.74b 0.16

9.70a 8.77a 10.20a 9.47a 10.29a 9.80a 9.45a 0.35

3.15a 2.11b 2.99c 2.23b 3.28a 1.60d 1.91e 0.03

6.22a 6.21ac 6.17d 6.25b 6.21ac 6.18cd 6.18cd 0.01

Control S2.5 S5 W2.5 W5 N2.5 N5 SEM

74.25a 68.19b 64.85c 58.31d 51.53e 50.69e 41.59f 0.28

Redness a* 9.13a 4.57b 3.86c 0.28d 0.70d 6.44e 6.98f 0.10

Yellowness b* 6.09ae 12.14b 16.22c 15.43d 17.69f 6.56a 5.52e 0.18

Means with different letters in the same column are significantly different (P < 0.05). SEM: standard error of the mean. * For sample denomination see Table 1.

Means with different letters in the same column are significantly different (P < 0.05). SEM: standard error of the mean. * For sample denomination see Table 1.

would supply only 1.77% TDF when added to the meat system at a concentration of 5%. The samples presented slight differences in pH (Table 3) which, although statistically significant in some cases were not quantitatively important.

Yellowness values were highest in meat samples containing brown seaweeds (Wakame and Sea Spaghetti). On the other hand addition of Nori, at any concentration, produced no change with respect to the control. The observed variations in the colour parameters of the meat products induced by the addition of seaweeds are consistent with the colour characteristics of the brown and red seaweeds used in the formulation (Table 2).

3.3. Surface colour Colour was evaluated to detect tendencies for seaweed addition to cause changes in gel/emulsion meat systems, given that colour is one of the main parameters determining consumer acceptance of a product. In reformulated products, changes in colour parameters have been reported in connection with fat, water and meat pigment contents (Pietrasik, 1999). In the present research, the experimental conditions determined that the different samples were formulated with constant proportions of meat and pork backfat, so that there was very little variation in the level of water added (Table 1). Hence, the colour changes observed in this study could basically only have been produced by the type and concentration of the seaweeds added. Colour parameters for the cooked gel/emulsion systems with added seaweeds are presented in Table 4. The proportion and type of the added seaweeds affected (P < 0.05) the colour attributes (L*, a*, and b*) of samples. With reference to the control, the presence of seaweeds caused a decrease of lightness (L*), which was all the more pronounced the larger the amount of seaweeds added. Comparatively speaking, addition of Nori produced the largest decrease of L*, which presented lowest levels (55% of the control value) in the sample with 5% Nori (Table 4). The presence of seaweed generally reduced (P < 0.05) a* values of gel/ emulsion systems (Table 4). However, the effect did vary according to the type and proportion of seaweed added. There was a direct relationship between the percentage of seaweed added and the redness, which declined with Sea Spaghetti and increased with Nori. Differences in a* values were not found (P > 0.05) in Wakame samples. Unlike the case of parameters L* and a*, the presence of Sea Spaghetti and Wakame favoured the formation of yellow shades (b*) in meat products (Table 4). This effect was more pronounced the higher the proportion of added seaweed.

3.4. Emulsion stability Emulsion stability of the different systems was affected by the type and proportion of seaweed added (Table 5). Control samples presented good emulsion stability, with TFR, WR and FR values similar to those reported elsewhere for this type of meat systems (Jime´nez-Colmenero et al., 2005). This behaviour was to be expected since NaCl at the concentration used in this formulation (2.0%), solubilizes meat proteins, thus contributing to the formation of a protein gel/emulsion matrix with good water- and fatbinding properties upon heating. Incorporation of Sea Spaghetti and Wakame led to a decrease (P < 0.05) of TFR, WR and FR in the gel/emulsion systems. In general, emulsion stability of these samples was improved when the amount of added seaweed was increased (Table 5). In fact, practically no fluid was released by meat samples formulated with 2.5% and 5% Wakame and with 5% Sea Spaghetti (Table 5). The effect of adding Nori was different. With concentrations of 2.5%, the emulsion stability of meat sample decreased; with 5% it improved considerably, to the extent that the water- and fat-binding properties were comparable to those recorded with the other two seaweeds (P > 0.05) when added at the same concentration (Table 5). Generally speaking, it was found that binding properties were better in systems made with brown seaweeds (Wakame and Sea Spaghetti) than with red seaweed (Nori). Note that the products with added seaweed contained less NaCl (0.5%) than the control (Table 1). A lower concentration of NaCl is associated with less capacity to solubilize protein, which generally means that heat-induced gels have poorer water- and fat-binding properties. The fact that emulsion stability was greater in samples with added sea-

S. Cofrades et al. / Meat Science 79 (2008) 767–776 Table 5 Emulsion stability measured as total fluid release, water release and fat release of gel/emulsion systems* Sample

Total fluid release (%)

Water released (%)

Fat released (%)

Control S2.5 S5 W2.5 W5 N2.5 N5 SEM

4.12a 1.85b 0.03c 0.01c 0.00c 6.53d 0.10c 0.10

3.85a 1.71b 0.03c 0.01c 0.00c 5.92d 0.08c 0.13

0.27a 0.14b 0.00c 0.00c 0.00c 0.39d 0.01c 0.01

Means with different letters in the same column are significantly different (P < 0.05). SEM: standard error of the mean. * For sample denomination see Table 1.

weeds than in the control despite their having less added NaCl (Table 5) shows that there was no such reduction in water- and fat-binding ability, possibly due to the presence of the seaweed. There are several factors that can influence the emulsion stability of meat systems with added seaweeds. Wong and Cheung (2000), suggested that the physicochemical properties of seaweeds may be determined mainly by two of the chemical components of seaweeds: dietary fibre and pro-

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tein. Obviously the presence of both components in a meat gel/emulsion protein matrix may affect the characteristics of a meat product, including its water- and fat-binding properties. There have been numerous studies on the effect of TDF on meat products using various kinds of fibre (oat, citrus, soy, wheat, etc.) or fibre-rich ingredients. Although there are contradictory findings, their use in cooked meat products generally improves hydration properties and fat holding capacity, reducing fat and water loss during cooking and increasing emulsion stability (Cofrades et al., 2000; Jime´nez-Colmenero et al., 2005; Thebaudin et al., 1997). Hydration properties and fat absorption capacity are both attributes of the fibre (Thebaudin et al., 1997). This behaviour is consistent with the fact that water- and fat-binding properties are generally better in systems made with brown seaweeds (Wakame or Sea Spaghetti) than with red seaweed (Nori) because the former supply more fibre (Table 2). Differences in the water-holding capacity of seaweeds are closely related to the polysaccharide composition of the dietary fibre fractions (Suzuki, Ohsugi, Yoshie, Shirai, & Hirano, 1996), which would account for the fact that the percentage of water released was lower in samples with Wakame added than in the systems formulated with Sea Spaghetti, in spite of the latter’s higher TDF and SDF content.

Fig. 2. Scanning electron micrographs (500 magnification) of gel/emulsion meat systems. (a) C: control, without seaweed added; (b) S5: sample with 5% Sea Spaghetti added; (c) W5: sample with 5% Wakame added and (d) N5: sample with 5% Nori added.

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On the other hand, the physicochemical properties of gel/emulsion systems depend on the possibility of associations between molecules (water and fat with seaweed components), so that particle size is a factor to be taken into account when considering the technological behaviour of these ingredients (Thebaudin et al., 1997). Larger particle sizes in dietary fibres are associated with open structures and better hydration properties and fat absorption capacity; nonetheless, these technological properties do not affect the product to which they are added (Sa´nchez-Alonso, Haji-Maleki, & Borderı´as, 2006). In this experiment, the smaller particle size of Wakame (Fig. 1b), once it was fully distributed throughout the meat system (Fig. 2c), meant a higher surface/volume ratio and hence more opportunity for its components, among then fibre, to interact with the medium, thus helping to endow the system with good water- and fat-binding properties (Table 5). The consequences of addition of seaweed protein for the emulsion stability of meat systems are harder to determine. In quantitative terms the levels of seaweed protein present in the meat systems ranged from 0.14% (S2.5) to 2% (N5). There have been various studies in connection with the biochemical and nutritional properties of seaweed proteins (Fleurence, 1999; Mabeau & Fleurence, 1993; Rupe´rez & Saura-Calixto, 2001). However, to our knowledge there have been none intended to assess their technological properties and hence their effect on emulsion stability, even although it has been widely noted that seaweeds appear to be an interesting potential source of food protein, offering considerable possibilities for the development of new foods or additives for human consumption (Fleurence, 1999). 3.5. Texture Texture profile analysis (Table 6) indicated that, in general, compared with the control sample, addition of Sea Spaghetti, Nori and Wakame increased (P < 0.05) hardness and chewiness and significantly reduced springiness and cohesiveness of the gel/emulsion systems. The increases of hardness and chewiness were greater in samples with 5% added seaweeds. The effect of seaweeds on Hd and Cw was most pronounced in samples containing Wakame and least pronounced in samples with Nori (Table 6). In a gel/emulsion system, lower NaCl concentration implies less solubilized protein, and hence there may be insufficient protein aggregation to form a strong protein network. The fact that no such effect was observed on texture parameters (Table 6) suggests that seaweeds can be used to overcome texture problems in low-salt products. A variety of approaches to sodium chloride reduction have been assayed in meat processing (Collins, 1997). The gel/emulsions systems studied present similar meat protein and fat contents; this means that, as in the case of emulsion stability, the effect of incorporation of seaweeds on meat product texture has to be assessed through the role played by their principal components, chiefly fibre.

Table 6 Texture profile analysis of meat batters* Sample

Hardness (N)

Springiness (mm)

Cohesiveness

Chewiness (N mm)

Control E2.5 E5 W2.5 W5 N2.5 N5 SEM

16.28a 21.91b 32.96c 26.02d 34.53e 19.37f 28.79g 0.32

8.15a 8.13ab 7.98bc 8.01abc 7.87cd 7.69e 7.71de 0.04

0.497a 0.489bc 0.486bc 0.488bc 0.492ab 0.485c 0.476d 0.00

65.98a 87.02b 127.75d 101.83c 133.70e 70.87a 105.6c 1.26

Means with different letters in the same column are significantly different (P < 0.05). SEM: standard error of the mean. * For sample denomination see Table 1.

Dietary fibres from different sources have been studied alone or combined with other ingredients for formulation of different meat products, with a view, among other things, to improving texture. Reported findings have been contradictory for various reasons, but it has generally been found that the addition of different kinds of fibre (soy, wheat, cereal and fruit) to cooked meat emulsions augments hardness (Cofrades et al. 2000; Ferna´ndez-Gine´s et al., 2005; Jime´nez-Colmenero et al., 2005). The addition of dietary fibres to foods modifies the texture and stability in ways determined by the processing conditions, but the mechanisms differ depending on the solubility of the fibres. Insoluble fibres can influence food texture thanks to their water-holding ability and swelling properties, (Thebaudin et al., 1997). Insoluble fibre can enhance the consistency of meat products through the formation of an insoluble three-dimensional network (Backers & Noll, 1998) capable of modifying rheological properties of the continuous phase of emulsions. Therefore, the explanation for the different effects of Sea Spaghetti, Wakame and Nori on the textural properties of the meat systems studied may lie in the differences in proportion, composition and characteristics of the dietary fibre that they contain. For instance, the two brown seaweeds Wakame and Sea Spaghetti, which present similar behaviour but different to that of Nori, contain more fibre and also present a higher proportion of insoluble fibre (Table 2). Also relevant in that respect are the gelling properties associated with the presence of calcium ions and alginates, both of which are present in higher proportions in the brown seaweeds (Jime´nez-Escrig et al., 2001). And yet another element associated with the effect of adding Wakame on meat product texture is the seaweed particle size. It is smaller in Wakame than in Sea Spaghetti or Nori (Fig. 1a–c), which means that the insoluble three-dimensional network formed is more fully distributed and hence has more opportunity to interact with the medium, in this case meat components (Fig. 2c). These mechanisms can help stabilize the structure of a gel/emulsion by modifying the rheological properties of the continuous phase (Thebaudin et al., 1997). This favours the formation of a more rigid protein

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gel matrix (Table 6) with better water- and fat-binding properties (Table 5). As in the case of emulsion stability, it was not possible to evaluate the effect of seaweed protein on the texture of the protein matrix. 3.6. Microstructure Micrographs of meat systems (Fig. 2a–d) show that the presence of seaweeds affected some characteristics of the gel/emulsion structure. Control sample presented a dense and compact protein matrix characteristic of heat-induced protein gels (Fig. 2a). In general the presence of seaweeds caused the formation of a more heterogeneous and spongy bulk meat protein matrix (Fig. 2b–d), but some other morphological aspects were dependent on the type of seaweed. These are the result of differences in physical and chemical characteristics of the seaweed powder used. Unlike the case of added Wakame, gel/emulsion samples containing Sea Spaghetti and Nori (Fig. 2b and d) contained some structures that were compatible with seaweed particles. This was presumably due to differences in the particle size of the powdered seaweeds used (Fig. 1a–c). The degree to which the added non-meat ingredient interacted with meat protein network structures, and the consequences of this for the gelation process, are factors that affect the physicochemical properties of the system (Carballo, Ferna´ndez, Barreto, Solas, & Jime´nez-Colmenero, 1996). For example, non-meat ingredients (e.g. egg white, walnut, etc.) which are not integrated (superimposed) in the meat matrix may interfere in the formation of a thermal gel matrix, producing softer structures (Jime´nez-Colmenero et al., 2003; Ayo, Carballo, Solas, & Jime´nez-Colmenero, 2005). The results of this experiment indicate that all three added seaweeds were adequately integrated, but particularly Wakame (Fig. 2c) thanks to its smaller particle size. This behaviour favours the formation of harder gel/emulsion networks (Table 6) with better water- and fat-binding properties (Table 5). Ferna´ndez-Martı´n et al. (2000) examined the microstructure of meat products containing dietary fibre and reported that apple fibre seemed suitable for integration in the meat protein matrix. 4. Conclusions The addition of seaweeds to meat emulsion based products is of great interest for technological and functional reasons. The seaweeds had an important influence on the properties of gel/emulsion meat systems, favouring the formation of harder and chewier structures with better waterand fat-binding properties, an effect that was particularly pronounced with Wakame. This behaviour was observed using much smaller amounts of NaCl (0.5%) than are commonly used in the preparation of meat products. Such technological attributes open up interesting prospects for the use of seaweeds in the formulation of healthier meat products to overcome technological problems associated with low-salt products, including problems concerning water-

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and fat-binding properties and texture. Moreover, from a nutritional point of view, the addition of seaweeds to meat products could help enhance their potential health-beneficial properties by providing not only dietary fibre but also other bioactive components such as antioxidant polyphenols or carotenoids. Such meat products with added seaweeds could help to address consumer demands for healthier functional foods. Acknowledgments This research was supported under project AGL200507204-CO2-02, Plan Nacional de Investigacio´n Cientı´fica, Desarrollo e Innovacio´n Technolo´gica (I+D+I). The authors thank the Spanish Ministerio de Educacio´n y Ciencia for Ms. Lo´pez-Lo´pez predoctoral fellowship. Thanks are due to Algamar S.A. for supplying the seaweeds. References Anandh, M. A., Lakshmanan, V., Mendiratta, S. K., Anjaneyulu, A. S. R., & Bisht, G. S. (2005). Development and quality characteristics of extruded tripe snack food from buffalo rumen meat and corn flour. Journal of Food Science and Technology-Mysore, 42(3), 263–267. AOAC (2000). Official methods for analysis of AOAC International (17th ed.). Maryland, USA: Association of Official Analytical Chemistry. Arihara, K. (2006). Strategies for designing novel functional meat products. Meat Science, 74(1), 219–229. Ayo, J., Carballo, J., Solas, M. T., & Jime´nez-Colmenero, F. (2005). High pressure processing of meat batters with added walnuts. International Journal of Food Science and Technology, 40(1), 47–54. Backers, T., & Noll, B. (1998). Dietary fibres move into meat processing. Fleischwirtschaft, 78(4), 316, 319–320, 344. Bligh, E. G., & Dyer, W. J. (1959). A Rapid Method of Total Lipid Extraction and Purification. Canadian Journal of Biochemistry and Physiology, 37(8), 911–917. Bourne, M. C. (1978). Texture Profile Analysis. Food Technology, 32(7), 62–65. Carballo, J., Ferna´ndez, P., Barreto, G., Solas, M. T., & Jime´nezColmenero, F. (1996). Morphology and texture of bologna sausage as related to content of fat, starch and egg white. Journal of Food Science, 61(3), 652–655. Cofrades, S., Guerra, M. A., Carballo, J., Ferna´ndez-Martı´n, F., & Jime´nez-Colmenero, F. (2000). Plasma protein and soy fiber content effect on bologna sausage properties as influenced by fat level. Journal of Food Science, 65(2), 281–287. Collins, J. E. (1997). Reducing salt (sodium) in processed meat, poultry and fish products. In Production and processing of healthy meat, poultry and fish products. In A. M. Pearson & T. R. Dutson (Eds.). Advances in meat research series (Vol. 11, pp. 282–297). London: Chapman & Hall. Connor, W. E. (2000). Importance of n-3 fatty acids in health and disease. American Journal of Clinical Nutrition, 71(1), 171S–175S. Davis, T. A., Llanes, F., Volesky, B., Dı´az-Pulido, G., McCook, L., & Mucci, A. (2003). H-1-NMR study of Na alginates extracted from Sargassum spp. in relation to metal biosorption. Applied Biochemistry and Biotechnology, 110(2), 75–90. Ferna´ndez-Gine´s, J. M., Ferna´ndez-Lo´pez, J., Sayas-Barbera, E., & Pe´rez´ lvarez, J. A. (2005). Meat products as functional foods: A review. A Journal of Food Science, 70(2), R37–R43. Ferna´ndez-Gine´s, J. M., Ferna´ndez-Lo´pez, J., Sayas-Barbera, E., Sendra, ´ lvarez, J. A. (2004). Lemon albedo as a new source of E., & Pe´rez-A dietary fiber: Application to bologna sausages. Meat Science, 67(1), 7–13.

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