Effect of inulin, β-Glucan and their mixtures on emulsion stability, color and textural parameters of cooked meat batters

Meat Science 94 (2013) 320–327

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Effect of inulin, β-Glucan and their mixtures on emulsion stability, color and textural parameters of cooked meat batters D. Álvarez a,⁎, S. Barbut b a b

Department of Food Technology, Human Nutrition and Food Safety, University of Murcia, 30071 Murcia, Spain Department of Food Science, University of Guelph, Ontario, N1G 2 W1 Canada

a r t i c l e

i n f o

Article history: Received 30 September 2011 Received in revised form 9 February 2013 Accepted 19 February 2013 Keywords: Fat reduction Glucan Inulin Meat emulsion TPA Microstructure

a b s t r a c t The effects of fat level (20.0, 12.5 and 5.0%), Inulin (gel-IG, and powder-IP) and β-Glucan (βG) on emulsion stability, color, textural characteristics and microstructure of cooked meat batters were investigated. Reducing fat to 5.0% increased cooking loss and decreased emulsion stability, lightness, hardness and fracturability of cooked emulsions. Inulin, βG, and their mixtures were used as fat replacers in low fat formulations. Adding IP provided better emulsion stability compared to IG, which had no significant effect on stability. IP also produced harder (27–34 N) low fat products with a high fracturability (26–29 N). On the contrary, emulsions containing IG resulted in creamy and softer characteristics. The results were supported by light micrographs, which indicated that appropriate addition of IG and βG mixtures (3%-IG & 0.3%-βG, 6%-IG & 0.6%-βG) could compensate for some of the changes brought about by fat reduction, and maintained several of the textural characteristics of the product as well as reducing cook loss. © 2013 Elsevier Ltd. All rights reserved.

1. Introduction Several health problems, such as obesity and cardiovascular diseases, can be associated with excessive consumption of highly saturated animal fats (O'Neil, 1993). As a result, consumer awareness of the connection between nutrition and health has risen (Jiménez Colmenero, 2000). The health benefits derived from fat reduction in foods have been recognized in the prevention and treatment of different illnesses (Dentali, 2002). However, fat is very important in producing desirable sensory characteristics of food products including processed meat items. In many cases, low fat foods have been largely rejected by the consumers because they were considered less juicy, firmer, more rubbery, darker in color and overall less acceptable than traditional meat products (Keeton, 1994). The reduction of fat in meat emulsions can also provoke changes in emulsion stability parameters, such as fat and water losses during cooking, and thus affecting the final quality (Álvarez et al., 2007). Manufacturers have introduced several modifications in an attempt to offset the detrimental effects of fat reduction. They include the use of non-meat ingredients to improve the texture and the water-holding capacity and/or the adaptation of procedures to modify the composition of final products (García, Domínguez, Gálvez, Casas, & Selgas, 2002). Fat reduction and the production of new reduced calorie products have been a commercial goal leading to the introduction a new category of meat products characterized as light/lite (Ambrosiadis, Vareltzis, & Georgakis, 1996). The addition of dietary fibers, such as Inulin or β-Glucan, can also be considered a viable way ⁎ Corresponding author. Tel.: +34 868 88 47 11; fax: +34 868 88 41 47. E-mail address: [email protected] (D. Álvarez). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.02.011

to reduce animal fat in meat products, by means of using natural ingredients as fat replacers. Dietary fiber can lead to a compact gel formation due to the fiber´s ability to retain fat and water (Fernández-Ginés, Fernández-López, Sayas-Barberá, & Pérez-Álvarez, 2005), which can improve structural integrity, yield and adhesiveness in reduced fat products (Tokusoglu & Kemal, 2003). Inulin is a soluble dietary fiber consisting of different levels of polymerization; e.g., up to sixty monomers of fructose bound by β-2-1 glycosidic linkages. It has been used as a fat replacer in low-fat sausages to improve quality of the final product (Nitsch, 2006). Inulin is currently used in several non-meat food systems as it can enhance the rheological and textural properties, improving the stability of foams and emulsions. Franck (2002) indicated that Inulin can be used to give meat products a creamier and juicier mouthfeel without compromising taste and texture. Inulin is considered a functional food ingredient and it is used in different foods as a fat substitute, energy reducing agent, improving water-holding and emulsion stability, as well as to modify the texture and viscosity of foods (Boeckner, Schnepf, & Tungland, 2001). Among its main health benefits, it has been reported to reduce the risk of arteriosclerosis, prevent osteoporosis (Frank, 2000) control the level of glucose in blood (Jackson, Taylor, Clohessy, & Williams, 1999), maintain low levels of triglycerides and cholesterol in serum, and stimulate the immune system (Desmedt & Jacobs, 2001). Barley β-Glucan is another non starch polysaccharide reported useful as a fat replacer in sausages, while providing water retention by thickening and/or gelling due to its hydrocolloid characteristics (Morin, Temelli, & McMullen, 2004). Oat products rich in soluble fibre components, such as β-Glucan, have a very positive image due to their health benefits and ability to reduce blood serum cholesterol (Hecker,

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Meier, Newman, & Newman, 1998) and regulating blood glucose levels (Yokoyama et al., 1997). The aims of this study were to investigate the effects of Inulin, β-Glucan and their mixtures in low fat meat emulsions and evaluate their contribution to cooking loss, color, and texture. In addition, their interaction within the meat system was evaluated by examining the microstructure of the meat matrix, during emulsification and cooking. 2. Material and methods 2.1. Ingredients Fresh pork leg meat (mixture of M. biceps femoris, M. semimembranosus, M. semitendinosus, M. gracilis and M. aductor) and backfat from pig carcasses weighting about 100 kg, were obtained from the abattoir of the Animal Science Department (University of Guelph) and processed within 24-h postmortem. Excess fat and connective tissue were trimmed. Meat and backfat were separately chopped at low speed in a bowl chopper (Mainca model CM-14, Granollers, Barcelona, Spain) for 30 s, weighed, packed into nylon coextruded bags (Norstar Corp., Brampton, ON, Canada), item # CN7P (standard thickness, 3.0 μ; oxygen transmission, 0.02 cc/100 in2 day, and water vapor transmission, 0.26 g/100 in2 day), vacuum sealed with a Multivac packaging machine (mod. A300/16, Wolfertschwenden, Germany) equipped with a vacuum pump of 21 m 3/h, and frozen at −18 °C until use, within two months. Inulin was used as a gel (IG) form (Frutafit® Inulin TEX; Sensus America LLC, NJ, USA) or Inulin powder (IP) concentrate (Raftiline® ST Inulin, Beneo–Orafti Ltd., Belgium) at 3% or 6% level (w/w). The Frutafit® Inulin TEX (96.7% concentrate powder) was made into a gel by hydrating (36.19 g powder/100 ml H2O) to get a 35% concentration in gel form. It was then heated at 85 °C for ~6 min while stirring at ~250 rpm on a hot plate until dissolved. The aqueous solution was cooled, poured into glass tubes, and left at 20 °C to set the gel structure. Appropriate amounts were used to reach the desired final content in the meat batters (Table 1). The Raftiline® ST Inulin (90% dry matter) was directly incorporated as a powder into the meat batters. β-Glucan was used in a gel form (Viscofiber® Oat β-Glucan; Neutracetical Canada Inc., Edmonton, AB, Canada) at three different concentrations (w/w), 0.15%, 0.3% and 0.6%. The Viscofiber® (46.7% β-Glucan concentrate powder) was hydrated (21.41 g powder/100 ml H2O) to produce a

321

10% gel. Mixtures were heated until boiling (approximately 100 °C) and manually stirred for a few seconds until a thick paste was obtained. The solutions were allowed to cool to room temperature and then stored at 4 °C overnight. Appropriate amounts of β-Glucan gel were used to reach the desired final content in the meat batters (i.e., 15, 30 and 60 g for batches that had 0.15%, 0.3% and 0.6% of β-Glucan, respectively). Inulin Gel and β-Glucan mixtures (3% IG & 0.3% βG, 6% IG & 0.6% βG) were also evaluated to establish the effect of the combination. Selection of these amounts was based on preliminary studies in which no technological disadvantages were observed; the parameters studied included emulsion stability (cooking and fat losses), color (L*, a*, b* coordinates) and texture (hardness, rupture force, etc.) in products with 20%, 12.5% and 5% fat. The rest of the ingredients included: salt (Sifto, Bruce Edmeades Co. Kitchener, ON, Canada), curing salt (Hela Rapid Cure with 6.4% sodium nitrite, Herman Laue Spice Co. Inc., Uxbridge, ON, Canada), water and ice (Table 1). 2.2. Batter preparation The experiments were performed by examining two reduced fat levels (12.5%, 5.0%) with the addition of natural polysaccharides: Inulin (Gel, 96.7% dietary fiber, 0.3% carbohydrates, 0% protein, 0% fat, 2.8% moisture, 6.28 MJ kg−1; Powder, 90%, 8%, 0%, 0%, 1.8% moisture and 5.02 MJ kg−1, respectively), β-Glucan (46.7% dietary fiber, 29.4% carbohydrates, 8.6% protein, 4% fat, 5.3% moisture and 15.70 MJ kg−1) or Inulin/β-Glucan mixtures in different proportions. Batter formulations were prepared using a 1 kg batch per treatment (Table 1). Overall, twenty treatments including the control treatments of reduced fat levels (C-12.5 fat and C-5 fat; Table 1), were manufactured in 3 independent replications (60 batches). An additional batch containing a regular amount of fat (20%) without adding other natural carbohydrate was prepared by replicate (3 batches) as a control reference (C-20.0 fat; Table 1) to evaluate the effect of fat reduction (12.5% and 5% fat) on technological properties of meat batters. The proximate composition (AOAC, 1996) of the raw ingredients was; 72.61% moisture, 21.28% protein, 5.11% fat and 1.00% ash for trimmed pork meat, and 7.61% moisture, 3.17% protein, 89.19% fat and 0.03% ash for backfat. Thawed meat (overnight at 4 °C) was pre-cut in the bowl chopper (Mainca model CM-14) for 30 s at the low speed setting. Water and salt were directly added and all chopped for 30 s at high speed (3425 rpm). Ice was

Table 1 Treatment number, formulations used in preparing the meat emulsions and average values of principal microscopic parameters studied in cooked meat emulsions1. Treatment # (%fat)

Ingredient

Fat (g)

Inulin Gel (IG; g)

Inulin Powder (IP; g)

β -Glucan (BG; g)

Water/ice (g)

Area (μm2)

1 (20) 2 (12.5) 3 (12.5) 4 (12.5) 5 (12.5) 6 (12.5) 7 (12.5) 8 (12.5) 9 (12.5) 10 (12.5) 11 (12.5) 12 (5) 13 (5) 14 (5) 15 (5) 16 (5) 17 (5) 18 (5) 19 (5) 20 (5) 21 (5)

C-20.0Fat C-12.5Fat 3-IG 6-IG 3-IP 6-IP 0.15-BG 0.3-BG 0.6-BG 3-IG/0.3-BG 6-IG/0.6-BG C-5.0Fat 3-IG 6-IG 3-IP 6-IP 0.15-BG 0.3-BG 0.6-BG 3-IG/0.3-BG 6-IG/0.6-BG

190 106 106 106 106 106 106 106 106 106 106 22 22 22 22 22 22 22 22 22 22

0 0 86 171 0 0 0 0 0 86 171 0 86 171 0 0 0 0 0 86 171

0 0 0 0 33 67 0 0 0 0 0 0 0 0 33 67 0 0 0 0 0

0 0 0 0 0 0 15 30 60 30 60 0 0 0 0 0 15 30 60 30 60

30/160 30/244 30/158 30/73 30/211 30/177 30/229 30/214 30/184 30/128 30/13 30/328 30/242 30/157 30/295 30/261 30/313 30/298 30/268 30/212 30/97

1.80 1.40 1.21 3.40 11.1 12.6 6.42 1.81 4.80 4.55 3.84 1.65 4.69 3.69 7.56 6.56 4.57 1.69 4.35 3.98 2.81

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

1.02 A 0.39de A 0.24e 1.11cde 2.11ª 2.53a 1.04b 0.29de 2.51bc 2.11bc 1.73cd 0.33d A 1.72bc 0.92cd 2.86a 3.55ab 0.65bc 0.39d 1.62bc 0.96cd 0.73cd

Roundness 1.92 1.77 1.70 2.40 2.52 2.58 2.71 2.08 2.34 2.71 2.55 1.92 2.63 2.47 2.47 2.36 2.50 1.93 2.73 2.53 2.16

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.40 A 0.14c A 0.11c 0.20ab 0.22a 0.23ª 0.22ª 0.14bc 0.47ab 0.45ª 0.40a 0.11d A 0.39ab 0.24abc 0.26abc 0.24bc 0.13abc 0.18d 0.29ª 0.24abc 0.30cd

C = Control emulsions made with 20.0, 12.5 and 5.0% fat (Treatments 1,2 and 12, respectively). IG = Inulin Gel. IP = Inulin Powder. BG = β-Glucan. Averages with same superscript are not significantly different (P b 0.05). Averages are shown for each fat level. Differences among control emulsions (C-20.0, C-12.5 and C-5.0) are noted with capital letters (N = 3). Area and roundness variables refer to fat globules observed in the light microscopic analyses. 1 N = 60; All made with meat (600 g), salt (17.7 g) and curing salt (2.3 g; contains 6.4% sodium nitrite).

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then added and mixture chopped for 1 min at high speed. This was followed by adding the thawed pork fat and/or fat replacements (IG, IP, βG), and the mixture was then chopped for another 4 min (total chopping time 6 min, final temperature b 12 °C). Temperature was monitored by a thermocouple probe (Cole Parmer, Mod. 90201–10, Montreal, Canada). Each batter was vacuum-packed (Multivac, Model A300/16, Sepp Haggenmüller KG, Wolfertschwenden, Germany) in polyethylene bags (CN7P-COEX, Norstar Corp., Brampton, ON, Canada) to remove trapped air. 2.3. Cooking loss Three 35 g raw batters were stuffed into 50 ml polypropylene tubes and centrifuged (Fisher Scientific TM Centrifuge, Model 225) at low speed for 30 s to remove any remaining small air bubbles. Tubes were cooked in a water-bath (Haake, Model W26, Karlsruhe, Germany) from 22 to 72 °C within 1.5 h. Liquid exudates were collected after cooling the test tubes in a cold-water bath for 5 min; results are expressed as the ratio of liquid expelled to raw batter weight.

following formula: (Perimeter2)/(4 x π x Area), considering a roundness = 1 for circular objects, and roundness > 1 for irregular objects. 2.7. Statistical analysis The experiment was designed as a randomized complete block with three independent replications where different ingredients were used (Table 1). Data were analyzed by the Statistical Analysis System (SAS®, version 9.01, 2002), using the analysis of variance (ANOVA) and the general linear model (GLM) procedure. Pearson correlation coefficient (r), the least squares means (LSM) and significance of treatments were calculated by using type IV sum of squares. LSM were considered to be statistically different when P b 0.05. 3. Results and discussion 3.1. Summary of the statistical analysis

Nine cylindrical cores (10 mm length × 16 mm diameter) per treatment were cut from the cooked emulsions. Core samples were compressed twice between two parallel plates using a texture analyzer (Texture Technologies Corp., Model TA.XT2, Scarsdale, NY, USA) to 75% of their original height, at a crosshead speed of 1.5 mm/s. The capacity of the load cell used was 25 kg (250 N). Hardness (N); fracturability (N), cohesiveness, gumminess (N), springiness (mm), adhesiveness (N s) and chewiness (N mm), were determined (Bourne, 1978).

Dependent variables tested for evaluating the effects of the different ingredients on the properties of meat emulsions were: color parameters (L*, a* and b*), meat emulsion stability (CLoss and FLoss) and textural parameters (Table 2). Below is an initial overall description of the ANOVA, followed by specific effects of fat level and other ingredients. One-Way ANOVA model was used to determine the main sources of variation within the dependent variables. Replicate (Rep), use of animal fat (Fat), Inulin Gel (IG), Inulin Powder (IP) and β-Glucan (βG), were the main effects in the ANOVA model. The main interaction “IG & βG” was also included. Replication effect was only significant for L*, b*, chewiness and hardness. The ANOVA model was highly significant for all the dependent variables studied. The presence of different fat levels was found to have a significant (P b 0.01) effect on L* and a*, emulsion stability (CLoss and FLoss) and textural parameters (cohesiveness and hardness). The main effect IG was highly significant (P b 0.001) only for the dependent variable hardness, while IP showed a significant effect with most dependent variables, excluding springiness, cohesiveness and adhesiveness. The main effect βG was highly significant (P b 0.001) for most of the dependent variables studied, and especially for emulsion stability and textural parameters; no significant effect on L* was detected. The interaction “IG & βG” had a significant effect on all textural parameters and emulsion stability, showing no significant effect on L* and a*.

2.6. Light microscopy

3.2. Influence of fat reduction on meat emulsions

Samples (2.0 × 2.0 × 0.5 cm) were cut from the centers of cooked meat batters, pre-fixed in 10% neutral buffered formalin for 10 h, followed by dehydrating in 70% isopropanol for 2 h, 95% for 1 h, and 100% for 4 h. The dehydrated samples were soaked in xylene for 2 h and then embedded in paraffin using an automated vacuum infiltration unit (Sakura Tissue-Tek VIP, Sakura Finetek, Torrance, CA). Samples were sectioned (Microtome HM 200, Eragoster, Walldoft, Germany) into 4–6 μm sections, allowed to float on water, and transferred onto glass slides. Slides were then dried in an oven at 65 °C for 40 min, deparaffinized in xylene (x3 washes), isopropanol (100% ×3), (95% ×1) and (70% ×2); each for 2 min, washed in water, placed in periodic acid Schiff’s reagent (1%) for 5 min, rinsed in water, counter stained with Hematoxylin for 4 min, washed in water, dipped 4–5 times in acid alcohol (1% HCl in 70% isopropanol), and blued in alkaline water (tap water with few drops of ammonium hydroxide). A cover slip was mounted on top and specimens were observed using a light microscope (Model BX60, Olympus Optical Co, Ltd., Tokyo, Japan). Pictures were captured by a computerized image analysis system (Image-Pro Plus, Version 6.0, Media Cybernetics Inc. Silver Spring, MD) and saved as TIF files. The area of fat globules was determined by the Imaging-Pro Plus software through the calculation of comprised pixels having intensity values within the selected range. Roundness of fat globules was determined by the

Reducing the fat content from 20.0% to 5.0% caused a significant (P b 0.05) increase in overall cooking losses and a decrease in fat loss of meat emulsions (Fig. 1). According to Honikel and Hamm (1994), the low cooking loss observed in high fat samples is due to the positive action of fat to stabilize the batter by acting as a spacer within the protein network. Similar results are shown here. The 2% fat exudates versus 0.2% in the low fat product is a reflection of the overall amount of fat (20.0% vs 5.0%). Piñero et al. (2008) indicated that this trend is probably due to a low density meat protein matrix, along with some fat instability. Mittal and Barbut (1994) observed a similar inverse relationship between cooking losses and fat content in frankfurters. In addition, Crehan, Hughes, Troy, and Buckley (2000), indicated that as fat level in meat samples decreased, cooking loss increased as added water/ice increased. ANOVA results showed high interaction between emulsion stability and fat content of the products (Table 2). Overall, both liquid and fat losses, observed in the low fat emulsions, indicate a decrease in emulsion stability, resulting in less binding and softer texture. Hughes, Cofrades, and Troy (1997) also found that cooking loss was affected by changing the fat and water content, observing a similar trend in emulsion stability. The results suggest that hydration properties and controlling cooking loss are very important in maintaining proper stability in emulsified meat products. Previous research indicated that fat content

2.4. Color measurement The color (9 inner sections/treatment) was measured on cooked samples using a Hunter Lab colorimeter (Mini Scan MS/S, Hunter Lab., Reston, VA, USA) with a D65 illuminant setting, and 10-degree standard observer. The measurement geometry and viewing area used was; 45° circumferential illumination; 0° viewing angle geometry, and 3.75 inch measurement area. Color was expressed according to the Commission International de l‘Eclairage (CIE) system and reported as Hunter L* (lightness), a* (redness) and b* (yellowness) values. 2.5. Texture profile analysis (TPA)

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Table 2 Analysis of variance and F statistics1 for textural parameters, color values, cooking and fat losses. Parameter2

Model

Variation Source Rep

R L* a* b* CLoss FLoss Fract. Spring. Cohesv. Chew. Gumm. Adhesv. Hardness

2

0.61 0.90 0.69 0.95 0.74 0.95 0.74 0.88 0.94 0.96 0.91 0.97

F 6.16⁎⁎⁎ 35.5⁎⁎⁎ 8.66⁎⁎⁎ 72.8⁎⁎⁎ 11.2⁎⁎⁎ 79.9⁎⁎⁎ 11.2⁎⁎⁎ 28.2⁎⁎⁎ 56.4⁎⁎⁎ 84.4⁎⁎⁎ 41.8⁎⁎⁎ 134⁎⁎⁎

11.4⁎⁎⁎ ns

11.7⁎⁎⁎

IG & βG

F

F

F

F

ns

3.37⁎ 108⁎⁎⁎ 9.12⁎⁎⁎ 39.6⁎⁎⁎ 6.28⁎⁎ 143⁎⁎⁎

ns

ns

4.64⁎⁎ 12.9⁎⁎⁎ 122⁎⁎⁎ 11.0⁎⁎⁎ 6.30⁎⁎ 9.02⁎⁎⁎ 22.3⁎⁎⁎ 10.9⁎⁎⁎ 12.1⁎⁎⁎ 89.1⁎⁎⁎ 12.5⁎⁎⁎

ns

F 8.60⁎⁎ 30.8⁎⁎⁎

ns

3.93⁎

ns

ns

βG

IG

71.9⁎⁎⁎ 79.3⁎⁎⁎

ns

IP

Fat

ns ns

ns

ns

ns

ns

5.86⁎ 26.2⁎⁎⁎

ns

ns

5.14⁎⁎

ns

ns

ns

ns

ns

ns

5.18⁎⁎ 4.11⁎

75.0⁎⁎⁎ 141⁎⁎⁎

ns

ns

ns

ns

5.16⁎⁎

43.9⁎⁎⁎

13.6⁎⁎⁎

269⁎⁎⁎

17.8⁎⁎⁎ 149⁎⁎⁎ 7.15⁎⁎ 16.0⁎⁎⁎ 20.1⁎⁎⁎ 57.3⁎⁎⁎ 19.6⁎⁎⁎ 16.8⁎⁎⁎ 60.7⁎⁎⁎ 8.22⁎⁎⁎

1 N = 60; R2 = determination coefficient of dependent variables; F, ANOVA F-statistic; Degree of freedom (of dependent variables) for calculation error (DF error): equals to 49 - for the model, 13, for replication, Fat, IG, IP and IG-BG is 2, and for BG is 3. ⁎P b 0.05, ⁎⁎P b 0.01, ⁎⁎⁎P b 0.001, ns not significant. 2L*; lightness; a*, redness, b*, yellowness; CLoss = Cooking loss; FLoss = Fat loss; Fract. = Fracturability; Spring. = Springiness; Cohesv. = Cohesiveness; Chew. = Chewiness; Gumm. = Gumminess; Adhesv. = Adhesiveness.

influences the color of meat products (Crehan et al., 2000; Hughes et al., 1997). Our results also show that reducing fat from 20.0% to 5.0% caused a continuous decrease in L* (Fig. 1). The L* of cooked products varied from 62.5 (20.0% fat) to 60.3 (5.0% fat), but redness - yellowness did not differ appreciably among the treatments as the amount of lean meat did not change. The effect of fat on the textural parameters (Fig. 2) shows that fat reduction from 20.0% to 5.0% brought a decrease of 35% in hardness, and lower decreases in fracturability, gumminess and chewiness; significant for the hardness. Cofrades, Carballo, and Colmenero (1997) also found that high-fat frankfurters were harder than low-fat frankfurters. Fracturability showed a decreasing trend (Fig. 2), although not significant. Adhesiveness and springiness were not affected by fat content. However, cohesiveness showed a significant (P b 0.05) increase with a maximum value at the lowest fat level (0.28 at 5% fat). The results suggest a high correlation between some of the textural parameters and both fat and moisture contents of the meat products. 3.3. Influence of Inulin type on meat emulsion metrics The addition of IG to meat batters did not result in significant changes in emulsion stability (measured as cooking and fat losses; Table 3), textural parameters and color; values obtained were pretty C Loss CLoss

FFLoss Loss

similar and differences appeared independent of the amount added. Hardness was the only parameter showing a significant tendency to increase at higher IG concentration (6%). In general, the results show that it is possible to add up to 6% IG without affecting the typical structure of cooked emulsions. Table 3 also shows that many of the dependent variables studied were significantly affected by the Inulin Powder (IP). Overall, IP showed higher contributions towards emulsion stabilization (lower exudates) than Inulin used in the gel form. This is especially significant (P b 0.05) in reducing cooking loss when the maximum level of Inulin Powder (6%) was used. Cáceres, García, Toro, and Selgas (2004) observed a similar trend in cooking loss of sausages when using a soluble dietary fibre (SDF) Inulin Gel. They suggested that it could be due to SDF making the gel structure more compact and therefore preventing proteins from retaining the water. Carballo, Fernández, Barreto, Solas, and Jiménez Colmenero (1999), suggested that gels formed with polysaccharides favour the formation of a more compact and stronger heat-induced protein matrix, diminishing the links with water and thus increasing cooking loss. The differences in emulsion stabilization between Inulin types also suggests that thermal treatment could differently affect the structure of carbohydrate chains, conditioning Inulin Gel formation and therefore its ability to stabilize meat emulsion (i.e. in comparison to IP). According to Kim, Faqih, and Wang (2001), gel formation of different carbohydrates is affected by many factors including concentration

L*L*

25.0

63.0

30.0

C-20,0%

C-5,0%

20.0

61.5 61.0

15.0

60.5

10.0

Force (N)

20.0

Lightness

62.0

Exudate (%)

C-12.5%

62.5

25.0

15.0

10.0

60.0 5.0

59.5

5.0

59.0

0.0 C-20.0%

C-12.5%

C-5.0%

Control emulsions Fig. 1. Effect of fat reduction on cooking exudates (liquids and fat) and lightness coordinate of cooked pork emulsions. C = Control with 20.0, 12.5 and 5.0% fat; CLoss = Cooking loss; FLoss = Fat loss; L* = Lightness.

0.0

Hardness

Fracturability

Gumminess

Chewiness

Fig. 2. Effect of fat reduction on textural parameters (hardness, fracturability, gumminess and chewiness) of cooked pork emulsions. C = Control with 20.0, 12.5 and 5.0% fat.

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Table 3 Average values of cooking loss, color coordinates and textural parameters of cooked meat emulsion; showing the main effects of Inulin Gel and Inulin Powder1. Inulin Gel (%) 0% CLoss FLoss L* a* b* Fracturability (N) Hardness (N) Springiness (mm) Cohesiveness (ratio) Chewiness (N mm) Gumminess (N) Adhesiveness (N s)

Inulin Powder (%) 3%

a

22.1 ± 5.07 0.36 ± 0.29a 61.1 ± 1.31a 8.04 ± 0.20a 8.67 ± 0.40a 14.2 ± 1.58a 16.2 ± 2.40a 0.56 ± 0.04a 0.26 ± 0.02a 2.40 ± 0.40a 4.23 ± 0.47a −0.14 ± 0.02a

6% a

21.3 ± 3.95 0.21 ± 0.17a 61.6 ± 1.45a 8.00 ± 0.24a 8.85 ± 0.37a 14.1 ± 1.52a 17.6 ± 1.67ab 0.56 ± 0.02a 0.25 ± 0.01a 2.49 ± 0.28a 4.42 ± 0.37a −0.16 ± 0.05a

0% a

20.1 ± 3.42 0.22 ± 0.16a 62.6 ± 1.22a 8.10 ± 0.21a 9.23 ± 0.31a 13.9 ± 1.59a 20.3 ± 2.73b 0.60 ± 0.05a 0.25 ± 0.02a 3.10 ± 0.70a 5.09 ± 0.80a −0.13 ± 0.04a

3% a

22.1 ± 5.07 0.36 ± 0.29a 61.1 ± 1.31a 8.04 ± 0.20a 8.67 ± 0.40a 14.2 ± 1.58a 16.2 ± 2.40a 0.56 ± 0.04a 0.26 ± 0.02a 2.40 ± 0.40a 4.23 ± 0.47a −0.14 ± 0.02a

6% ab

16.9 ± 3.21 0.12 ± 0.12a 60.0 ± 0.49ab 7.02 ± 0.18b 9.24 ± 0.13a 26.3 ± 1.78b 27.4 ± 1.82b 0.56 ± 0.04a 0.27 ± 0.01a 4.19 ± 0.47b 7.44 ± 0.45b −0.19 ± 0.07ab

11.6 ± 2.84b 0.18 ± 0.19a 59.3 ± 0.99b 6.33 ± 0.12c 9.52 ± 0.27a 29.4 ± 0.65a 34.7 ± 2.27a 0.55 ± 0.02a 0.27 ± 0.02a 5.30 ± 0.80a 9.52 ± 1.14a −0.27 ± 0.09b

CLoss = Cooking loss; FLoss = Fat loss. L*; lightness; a*, redness, b*, yellowness. 1 N = 60; Average with same superscript are not significantly different (P b 0.05).

of reactant, heating temperature, heating time, shear and pH. The authors suggested that minimal control of these factors may lead to an undesirable formation of Inulin Gel, which could affect gel strength and rheological properties (viscosity, storage and loss moduli). These changes in gel formation could lead to a deficient sol–gel transition in the further stages of the product preparation; e.g., chopping and cooking. Thus, according to Funami, Funami, Yada, and Nkao (1999), soluble polymers become insoluble to form a semi-solid structure (gel) due to association of polymer molecules within a polymer solution (sol). Color parameters L* and a* showed a significant (P b 0.05) decrease as IP was raised (Table 3). These results are close to those reported by Hadorn, Piccinali, Guggisberg, and Sutter (2007) who found a higher reduction in L* values when IP was added as compared to IG, observing similarly no significant differences in L* values after adding 7.5% Inulin Gel. Nowak, von Mueffling, Grotheer, Klein, and Watkinson (2007) also indicated a similar trend in Inulin Gel effect on L* and b* values in bologna-type sausages. Adding IP significantly increased fracturability, hardness, chewiness, gumminess and adhesiveness, but did not affect springiness and cohesiveness (Table 3). There was a tendency to raise fracturability when Inulin was added as a powder compared to gel. Hadorn et al. (2007) reported that the reduction of fracturability in bologna due to Inulin Gel addition was not only based on the substitution of fat but must also be seen as a characteristic of Inulin itself. However, our results indicate that the increase in fracturability, observed in the added IP products, was independent of the fat level used. This might be explained by the higher capacity of IP to hold water and producing a more compact meat structure, as will be discussed below. Similarly, hardness values were significantly higher in the low fat treatment when increasing IP level. This agrees with García, Cáceres, and Selgas (2006) who increased Inulin levels (2.5% to 7.5%) in Mortadela; both in the gel and powder form. Mendoza, García, Casas, and Selgas (2001), also showed higher hardness values in low fat, dry fermented sausages (6.3% fat) when using 7% Inulin powder, compared to control sausages (30% fat). 3.4. Influence of β-Glucan on meat emulsion metrics Increasing β-Glucan level resulted in a significant decrease in cooking losses of the low fat emulsions made with 0.6% βG (Table 4). As a result, moisture retention was higher as fat was raised from 5% to 12.5% and as β-Glucan level was raised from 0.15% to 0.6%. This was because of the greater amounts of water added (to the low fat products) coupled with the high water binding of β-Glucan. Moreover, Glucan powder was practically unaffected by the factors affecting gel formation (concentration, heating temperature and stirring speed), therefore providing a more consistent gel than Inulin (mainly due to their different compositions in both starch and total dietary fiber). Piñero et al. (2008) found a similar trend

on cooking yield in low fat beef patties when using 0.33% oat soluble fibre (β-Glucan) as a fat replacer. Warner and Inglett (1997) explained that this behavior could be due to the ability of β-Glucan to create a tridimensional network (as a result of its soluble fibre nature), capable of holding water and fat added, and thereby reducing cooking losses. Brummel and Lee (1990) reported that hydrocolloids can also bind a relative large amount of water while maintaining a fatlike texture in food systems. On the other hand, Morin et al. (2004) reported higher cooking losses in reduced-fat breakfast sausages made with 0.3% or 0.8% β-Glucan in comparison to control sausages manufactured with 22% fat (24%, 22% and 21% cooking loss, respectively), i.e., no significant differences between the two β-Glucan treatments. According to these authors, the similar high cooking loss values observed between the control and 0.8% βG samples could be explained by the fact that a decrease in fat could be offset by adding an appropriate amount of a hydrocolloid gum. Color results (Table 4) indicate that βG addition did not affect L*, while decreasing a* and increasing b*. Similar results of a* and b* were reported by Yilmaz and Daghoglu (2003) when using oat bran as fat replacer in meatballs, although L* values were significantly higher. This shift in color can result in cooked samples with a characteristic brown color, slightly different from the pink color in the cooked meat products studied here. However, Piñero et al. (2005) prepared low fat meat patties with oat soluble fibres (β-Glucan: 0.23%, 0.33% and 0.43%), and did not find changes in the sensorial color and appearance, concluding that the panel considered all treatments to have an equally acceptable color. In terms of texture, the control sausage (0% βG) showed the highest fracturability and hardness rating amongst the sausage samples (Table 4) and these textural parameters gradually decreased with increasing β-Glucan level. This indicates that β-Glucan is useful in preparing a low fat sausage with softer texture, as fat reduction by itself causes an increase in firmness. In agreement with Steenblock, Sebranek, Olson, and Love (2001), the reduction in hardness due to β-Glucan addition may also reflect the improved water holding in the frankfurters, as moisture content is well-recognized as an important factor influencing texture. These results are consistent with other researchers, who demonstrated that adding oat bran improved texture by decreasing products’ hardness (Carballo et al., 1999; Steenblock et al., 2001), as well as binding and retaining water to produce a more tender meat product, thereby reducing shear forces (Troy, Desmond, & Buckley, 1999). The rest of the textural parameters showed a similar behavior to the primary parameters as they are dependent on. Adhesiveness, which is not dependent on other parameters (e.g., hardness), showed a significant (P b 0.05) increase. This was also clearly observed during the testing, where β-Glucan produced sticky surfaces in the products to which it was added. The high degree of adhesiveness could possibly indicate an undesirable behavior which could result in

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Table 4 Average values of cooking loss, color coordinates and textural parameters of cooked meat emulsion; showing the main effect of β-Glucan and Inulin Gel–β-Glucan mixtures1. β -Glucan (%) 0% CLoss FLoss L* a* b* Fracturability (N) Hardness (N) Springiness (mm) Cohesiveness (ratio) Chewiness (N mm) Gumminess (N) Adhesiveness (N s)

Inulin Gel (%) & β-Glucan (%) 0.15%

a

22.1 ± 5.07 0.36 ± 0.29a 61.1 ± 1.31a 8.04 ± 0.20a 8.67 ± 0.40b 14.2 ± 1.58a 16.2 ± 2.40a 0.56 ± 0.04a 0.26 ± 0.02a 2.40 ± 0.40a 4.23 ± 0.47a −0.14 ± 0.02a

0.3% b

11.7 ± 4.72 0.16 ± 0.15a 60.7 ± 1.13a 7.80 ± 0.19ab 8.75 ± 0.13b 12.9 ± 2.12ab 14.2 ± 2.17ab 0.45 ± 0.09ab 0.21 ± 0.01b 1.45 ± 0.35b 3.04 ± 0.49b −0.32 ± 0.11b

0.6% bc

5.82 ± 1.99 0.39 ± 0.27a 59.9 ± 2.18a 7.81 ± 0.24ab 8.90 ± 0.54b 11.2 ± 1.95ab 12.4 ± 1.89b 0.51 ± 0.07ab 0.22 ± 0.01b 1.43 ± 0.40b 2.69 ± 0.47b −0.49 ± 0.09b

0% & 0% c

0.59 ± 0.45 0.04 ± 0.04a 61.5 ± 1.73a 7.61 ± 0.21b 9.80 ± 0.61a 10.4 ± 0.83b 11.6 ± 1.55b 0.43 ± 0.04b 0.21 ± 0.01b 1.09 ± 0.25b 2.47 ± 0.34b −1.05 ± 0.12c

3% & 0.3% a

22.1 ± 5.07 0.36 ± 0.29a 61.1 ± 1.31a 8.04 ± 0.20a 8.67 ± 0.40a 14.2 ± 1.58a 16.2 ± 2.40a 0.56 ± 0.04a 0.26 ± 0.02a 2.40 ± 0.40a 4.23 ± 0.47a −0.14 ± 0.02a

6% & 0.6% b

6.00 ± 1.30 0.39 ± 0.19a 62.2 ± 1.67a 7.83 ± 0.35a 9.51 ± 0.51a 10.5 ± 1.53b 13.1 ± 1.45b 0.44 ± 0.04b 0.20 ± 0.01b 1.17 ± 0.20b 2.65 ± 0.28b −0.51 ± 0.10b

3.25 ± 1.06b 0.15 ± 0.22a 61.5 ± 1.79a 7.81 ± 0.41a 9.85 ± 0.54a 8.90 ± 2.08b 13.5 ± 1.47ab 0.39 ± 0.03b 0.20 ± 0.01b 1.02 ± 0.13b 2.61 ± 0.21b −0.79 ± 0.20c

CLoss = Cooking loss; FLoss = Fat loss. L*; lightness; a*, redness, b*, yellowness. 1 N = 60; Average with same superscript are not significantly different (P b 0.05).

a difficulty to manage the sliced product flow, due to high stickiness. According to Nowak et al. (2007), in cooked meat products like Mortadella and bologna, adhesiveness must be kept at less than −0.1 Ns for acceptability and proper slicing management. The authors suggested the addition of citrate to sausages rather than phosphates for reducing adhesiveness values. This is because of the different effects of citrate inside the meat mix; i.e., leading to enhanced texture by decreasing pH and increasing water-binding capacity. In general, β-Glucan addition produced a slightly lower cohesiveness, but also affected the products’ elasticity (springiness). The gumminess and chewiness were also significantly lowered with increasing β-Glucan level, especially at the high βG concentration (Table 4).

3.5. Influence of Inulin and β-Glucan mixtures on meat emulsion metrics Increased levels of IG & βG mixtures showed a significant decrease in cooking loss, while no changes in fat loss, L*, a* and b* (Table 4). Cooking losses were reduced in comparison to adding IG alone, but were higher comparing to βG addition. These data suggest that Inulin Gel by itself can act directly on the meat proteins to minimize the interactions between β-Glucan and the matrix proteins, thereby decreasing the ability to stabilize the emulsion when compared to using βG by itself. The color was slightly darker and browner, similar to color of treatments obtained when βG was added. The addition of Inulin Gel and β-Glucan mixtures seems to have a positive effect on the texture and could therefore be a valuable alternative to compensate for the changes in texture due to adding Inulin Gel and β-Glucan by themselves. Improvements are observed in cooking loss and adhesiveness; both significantly reduced in comparison to adding IG and βG, respectively. Also, IG & βG mixtures had a positive effect on L* and a*, reducing the undesirable brown and dark appearance, typically seen in β-Glucan supplemented products. Overall, at this point it is difficult to draw precise conclusions

A

about the effect of Inulin Gel or β-Glucan supplementation in reducedfat emulsions, as the structural properties are affected not only by the type of dietary fibre used, but also by the fat reduction itself.

3.6. Light microscopy Fat reduction by itself did not show significant changes in the average area of the individual fat globule or roundness (Table 1). The actual distribution pattern, shape and size of the fat globules can be observed in the Fig. 3. The number of fat globules in the high-fat products was obviously higher than in the low fat products. In the high-fat emulsions (20.0%), few fat globules started to coalesce (Fig. 3C) and formed larger globules connected by channels. This coalescence of fat globules could have been the reason for fat loss detected in the high-fat products (Youssef & Barbut, 2009). In the low-fat samples (5.0%) the increased proportion of the protein matrix area compared to fat resulted in more shrinkage of the matrix (Fig. 3A) which could be responsible for the higher cooking losses (Fig. 1). The addition of ingredients such as Inulin or β-Glucan showed significant changes in the fat globules' microstructural parameters (area and roundness) of the cooked products (Table 1). The largest fat globules (area) were observed in 12.5% fat emulsions with IP added (11.1–12.6 μm2), followed by the 5% fat emulsions with IP added (6.56–7.56 μm2). These fat globule (area) values were also significantly higher than their respective controls (12.5% fat, 1.40 μm2; 5% fat, 1.65 μm 2). Increasing IG from 0.3% to 0.6% in the 12.5% fat emulsions, increased all fat globules parameters, with the exception of area which was not significant. Addition IG to low fat emulsions increased both fat globules parameters, compared to controls, with the exception of Treatment 3. Addition of 0.15% β-Glucan resulted in the largest fat globules area in both low fat formulations. The combined addition of IG and βG showed a significant increase in the fat globules area compared to the controls, especially in 12.5% low-fat formulations. Roundness of

B

FG

C MF FG

FG

MF Fig. 3. Light micrographs of meat batters: (A) 5% fat, (B) 12.5% fat, (C) 20% fat. MF = Muscle fibers; FG = Fat globules; Bar = 100 μm.

MF

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A

B

C

FG

D

IG

E

IP

BG

F

MF MF MD

FG

Fig. 4. Light micrographs of meat batters: (A) 12.5% fat–6% Inulin Gel (IG), (B) 12.5% fat–6% Inulin Powder (IP), (C) 12.5% fat–0.6% β-Glucan (BG), (D) 5% fat–6% IG, (E) 5% fat–6% IP, (F) 5% fat–0.6% BG. MF = Muscle fibers; FG = Fat globules; MD = Matrix discontinuity; Bar = 100 μm.

globules was increased in both 12.5% and 5% fat levels after adding Inulin or β-Glucan, indicating a low circularity of fat globules in comparison with their respective controls. The pattern of microscopic parameters described above is shown in Fig. 4. The 6% Inulin Gel added into emulsions made with 12.5% and 5.0% fat (Fig. 4A and D, respectively) show the distribution of IG in the meat matrix, revealing potential interference of binding within the matrix components. The meat matrix of emulsions supplemented with IG showed slightly more discontinuity, especially in the low fat (5%) samples (Fig. 4D), which could be the reason for the softer meat samples and higher cooking losses (Table 3). According to Morin et al. (2004), a high proportion of open spaces between the muscle fibers and cells can be interpreted as the presence of additional water, especially in the low fat samples. Hermansson (1985) suggested that a fine, uniform structure with numerous small pores, or open spaces, would probably result in more absorptive capacity and better water retention compared to coarse structures with larger pores. Fig. 4B and E show the addition of Inulin Powder (6%) into emulsions made with 12.5% and 5.0% fat, respectively. Contrary to IG, Inulin Powder is better distributed within the meat matrix, evenly filling available matrix spaces. The micrographs show that IP has a high capacity of hydration and swelling. As a result, the IP added products provided harder texture and low exudation during cooking, compared to IG. Fig. 4C and F show the addition of β-Glucan (0.6%) to emulsions made with 12.5% and 5.0% fat, respectively. β-Glucan treatments demonstrated a good distribution within the matrix, allowing tight connections between fat and meat, and forming compact matrices, which have the ability to hold large amounts of water. DeFreitas, Sebranek, Olson, and Carr (1997) also reported that carrageenans increased water-holding capacity and gel strength of meat protein networks. 4. Conclusions Fat reduction in cooked meat products resulted in a decrease of emulsion stability that corresponded with lower binding properties and softer texture. The results are in agreement with previous findings and suggest strong relations between textural parameters and fat/moisture content within meat products. Inulin Powder showed better emulsion stabilization than Inulin when added in a gel form. Inulin Gel exhibited a poor ability to hold water and fat during cooking as a result of its effect on matrix disruption, especially at the low fat level (5.0%).

Adding 6% Inulin Powder was sufficient to make the product harder, while the incorporation of Inulin in a gel form “transferred” its creamy characteristic and also made the sausage softer. β-Glucan could be a valuable fat-replacement as a result of its ability to help form dense matrices, which can hold large amount of water, and as shown here to also enhance textural parameters of reduced-fat products. However, adding Inulin or β-Glucan separately, revealed undesirable effects such as high cooking loss (e.g. IG addition), excessive hardness (e.g. by IP), or a high stickiness when βG was added by itself. The addition of Inulin Gel and β-Glucan mixtures could be a valuable alternative to improve stability and texture of low fat meat emulsions as they demonstrated positive effects on reducing cooking loss, and improving L*, a*, and adhesiveness; allowing compensation for the changes seen due to adding Inulin Gel and β-Glucan by themselves. Acknowledgments The authors wish to thank the Seneca Foundation (Consejería de Educación y Cultura. CC.AA. Murcia, Spain) for the financial support provided by the research project “Use of functional ingredients as promoters of healthy meat emulsions”, and the Ontario Ministry of Food and Agriculture for financial support. References Álvarez, D., Castillo, M., Payne, F. A., Garrido, M. D., Bañón, S., & Xiong, Y. L. (2007). Prediction of meat emulsion stability using reflection photometry. Journal of Food Engineering, 82, 310–315. Ambrosiadis, J., Vareltzis, K. P., & Georgakis, S. A. (1996). Physical, chemical and sensory characteristics of cooked meat emulsion style products containing vegetable oils. International Journal of Food Science and Technology, 31, 189–194. AOAC (1996). Official Methods of Analysis (15th ed.). Wash., D.C.: Association of Official Analytical Chemists. Boeckner, L. S., Schnepf, M. I., & Tungland, B. C. (2001). Inulin: A review of nutritional and health implications. Advanced in Food and Nutrition Research, 43, 1–63. Bourne, M. C. (1978). Texture profile analysis. Food Technology, 32, 62–66. Brummel, S. E., & Lee, K. (1990). Soluble hydrocolloids enable fat reduction in process cheese spreads. Journal of Food Science, 55(1290–1292), 1307. Cáceres, E., García, M. L., Toro, J., & Selgas, M. D. (2004). The effect of fructooligosaccharides on the sensory characteristics of cooked sausages. Meat Science, 68, 87–96. Carballo, J., Fernández, P., Barreto, G., Solas, M. T., & Jiménez Colmenero, F. (1999). Morphology and texture of bologna sausage as related to content of fat, starch and egg white. Journal of Food Science, 61, 652–655. Cofrades, S., Carballo, J., & Colmenero, F. J. (1997). Heating rate effects on high-fat and low fat frankfurters with a high content of added water. Meat Science, 47, 105–114.

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