Reduction of salt in pork sausages by the addition of carrot fibre or potato starch and high pressure treatment Meat Science 92 (2012) 481–489 Contents lists available at SciVerse ScienceDirect Meat S.
Meat Science 92 (2012) 481–489 Contents lists available at SciVerse ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci Reduction of salt in pork sausages by the addition of carrot fibre or potato starch and high pressure treatment Alberto Grossi a,⁎, Jakob Søltoft-Jensen b, Jes Christian Knudsen a, Mette Christensen a, Vibeke Orlien a a b Department of Food Science, Food Chemistry, Faculty of Life Sciences, University of Copenhagen, Denmark Danish Meat Research Institute — Danish Technological Institute, Roskilde, Denmark a r t i c l e i n f o Article history: Received 29 December 2011 Received in revised form April 2012 Accepted 18 May 2012 Keywords: Low salt sausages Hydrostatic pressure processing Uniaxial compression Napping Protein solubility Dietary ingredients a b s t r a c t The combined effect of high pressure processing (HPP) (400, 600 and 800 MPa) and carrot fibre (CF) and potato starch (PS) on low salt (1.2%) pork sausages was investigated and compared with high (1.8%) salt sausages Sausages had a marked increase in whitening with increasing content of fibre or starch, pressure level, and process temperature The degree of redness was mainly affected by pressure level and heat treatment An important finding regarding salt reduction was that the use of starch or fibre had more impact on textural properties than the level of salt since Young's modulus and strain at fracture were mainly affected by formulation and HPP Water binding capacity of low salt sausages was improved to the same level as high salt sausages with HPP and addition of CF or PS particularly by the addition of PS which produced sausages with better sensory properties than CF The sensory analysis showed that this approach is promising for producing low salt sausages © 2012 Elsevier Ltd All rights reserved Introduction Generally, consumers not consider pork sausages as healthy meat products due to a high level of fat and salt According to Tuomilehto et al (2001), a high level of sodium chloride has shown a negative impact on human health (Tuomilehto et al., 2001) Reduction of salt in meat products has therefore become an important research area during the last decade (Desmond, 2006; Doyle & Glass, 2010; Ruusunen & Puolanne, 2005) The Food Standards Agency (F.S.A., 2004) and the World Health Organization (2006), have published advisory guidelines for daily salt intakes recommending about a 50% reduction in the average salt intake per day However, in the meat industry addition of various salts to meat products is commonly used to improve food functionality and ensure food safety The addition of salts (commonly 1.5 to 2.5% of sodium chloride) to meat batters improves gelation, water binding capacity, fat retention, and cooking loss For health improvement, a variety of approaches have been applied to reduce the sodium content, among these are the substitution of sodium chloride with other types of salt or newer processing techniques (Desmond, 2006; Doyle & Glass, 2010) High pressure processing (HPP) is one of the newer technologies that have shown great potential for manufacturing meat products; indeed HPP offers a ⁎ Corresponding author at: Department of Food Science, Food Chemistry, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30 DK-1958 Frederiksberg C, Denmark Tel.: + 45 3533 3547; fax: + 45 3528 3344 E-mail address: atg@life.ku.dk (A Grossi) 0309-1740/$ – see front matter © 2012 Elsevier Ltd All rights reserved doi:10.1016/j.meatsci.2012.05.015 valuable alternative to the thermal pasteurization Nowadays, industrial HHP equipment can reach pressures of 600 MPa, which is a highly effective treatment for decreasing of bacterial load and extending the safe shelf life of refrigerated processed meat product (Jofre, Aymerich, Grebol, & Garriga, 2009) The promising application of HPP treatment is based on the pressure-induced increase in solubility of the myofibrillar proteins resulting in gelation and formation of the desired texture (Colmenero, 2002) HPP (100–300 MPa) was shown to induce a significant increase in the penetration force of raw meat batter (Carballo, Fernandez, & Colmenero, 1996) However, the pressureinduced gelation ability of meat proteins, especially in sausages, depends on the type of meat (protein system), the type of additives, and quite importantly temperature, since muscle proteins are also characterized by being thermolabile Some studies have been performed on the interaction between HPP and salt level on the functional properties of various types of meat product including pork and chicken In these studies it was reported that HPP technology is a viable process that partially compensates for the reduction of salt levels in meat product (Crehan, Troy, & Buckley, 2000; Jimenez-Colmenero, Fernandez, Carballo, & Fernandez-Martin, 1998; Sikes, Tobin, & Tume, 2009) Other studies have shown that the combination of HPP and different ingredients in the meat batters may improve or impair the functional properties of processed meat products (FernandezGines, Fernandez-Lopez, Sayas-Barbera, & Perez-Alvarez, 2005; Grossi, Soltoft-Jensen, Knudsen, Christensen, & Orlien, 2011; Hong, Min, Ko, & Choi, 2008; Trespalacios & Pla, 2007) The present authors have shown that HPP and incorporation of carrot dietary fibre (CF) in a comminuted meat emulsion, result in a high order of network organization 482 A Grossi et al / Meat Science 92 (2012) 481–489 leading to a harder texture and high water binding capacity (Grossi et al., 2011) The present study aims to investigate the combination of HPP and addition of CF and/or potato starch (PS) for production of sausages with reduced salt content by determining the effect of working pressure, temperature, and formulation on the physical properties of pork sausages Materials and methods 2.1 Product manufacture Sixteen batches of sausages were manufactured at the Danish Meat Research Institute, Roskilde Denmark (DMRI) The raw material of all the batches included (w/w) 56.2% of pork “topside” (semimebranosus; 2.2% fat, 75.3% water, 22.1% protein), 20% of loin fat (78.0% fat, 17.1% water, 4.9% protein), 22% of water, 1% of sodium chloride (99.4% NaCl and 0.6% NaNO3; 60 ppm NaNO3 in finished product) and either 0.2% or 0.8% sodium chloride without sodium nitrite The sixteen formulations differed in the content of salt, carrot fibre (CF; Hydrobind LP, Bolthouse Farms Inc., USA, extracted, dried fibre portion of carrots) and/or potato starch (PS; Superior potato starch, KMC, Denmark, unmodified starch from potatoes) Ingredient levels were based on screening results, recommendations from suppliers and specifically for salt levels based on common low end commercial level and future lowest possible end Acronyms were used to describe the different recipes and the different letters of the acronym indicate the concentration of the ingredients (see Table 1a and b): 1.8% NaCl with 0.6% NaNO2 (S: high salt content), 1.2% NaCl with 0.6% NaNO2 (s: low salt content), 3.8% PS (P: high content), 2% PS (p: low content), 1.5% CF (C: high content), and 0.5% CF (c: low content) All the ingredients (temperature of raw material 2–4 °C) were mixed in a vacuum high speed cutter (V30L, Kilia, Germany) at 2880 revs/min (3 of cutting time, followed by 20 rounds of backward knife rotation under full vacuum) until an end-point temperature of 12 °C of the emulsion was reached The meat emulsions were stuffed on a vacuum filling machine (VF50, Handtmann, Germany) in poly amide casings (naloflex, Kalle, Germany) of 60 mm in diameter and 140 mm in length (360 g each) After manufacturing the raw sausages were kept at 4–5 °C for 18–24 h until HPP 2.2 HPP and storage The sausages were vacuum packed and submerged in the pressurizing chamber of a QUINTUS Food Processing Cold Isostatic Press QFP-6 Table Representation of the sixteen different recipes a) Formulation with high content of salt (1.8%) and b) formulation with low content of salt (1.2%) Bold (fibre and starch) indicates the presence of carrot fibre and/or potato starch, and italic indicates the related quantity (fibre: no, 0%; low c, 0.5%; high C, 1.5%; starch: no 0, 0%; low p, 2%; high P, 3.8%) (Avure Technologies AB, Västerås, Sweden) with a pressure chamber of 0.9 l and a maximum operating pressure of 1000 MPa, 6.7 MPa/s = 402 MPa/min The sausages were brought to an internal temperature of or 40 °C followed by HPP treatment at 400, 600, or 800 MPa for at the respective temperature After HPPt, all the sausages (4 for each formulation treatment) were stored at °C in the dark for days before analysis of colour and texture Control sausages from all batches were: not HPP treated and heat treated at either or 40 °C in a water bath until a core temperature equal to the water temperature was reached In addition, heat treated sausages to a core temperature of 72 °C were used to simulate normal cooking conditions for sausage production 2.3 Colour The internal surface colour of the sliced sausages was measured using a Konica Minolta Spectrophotometer CM-600d (illuminant D65 and a 10° standard observer) with an aperture size of 40 mm and the corresponding Colour Data Software CM-S100w SpectraMagict™ NX (Konica Minolta Sensing, Inc., Japan) The instrument was calibrated with a white standard plate The values, expressed as CIE Lab L* (lightness), a* (redness), b* (yellowness), and reflectance spectra within the visual spectrum (400–700 nm in 10 nm intervals) were recorded Three sausages per formulation were sliced and colour measurements were performed on different positions within the cross section of each sausage A total of 20 measurements per treatment were obtained 2.4 Uniaxial compression Rheological properties of sausages were assessed by uniaxial compression (Instron 5564 Universal Testing Machine, Instron Ltd., High Wycombe, UK) For each formulation treatment, measurements were made on eight slices cut from three sausages Samples were cylindrical in shape (60 mm in diameter and 20 mm in height) The sample was compressed at a constant crosshead velocity of 50 mm/min Sample temperature was °C The compression steel plates were lubricated with a small amount of oil During compression, the displacement (mm) and corresponding force (F) were recorded The displacement and force data were converted to Hencky strain (ε) and corresponding stress (σ) The stress (σ), during compression, was calculated as the force (F) divided by the cross sectional area (A) of the sample, and multiplied by the height of the sample during compression (Ht) relative to the initial height (H0) of the sample: σ = (F/A) * (Ht / H0), as described previously (Grossi et al., 2011) The Hencky strain (ε) was calculated as follows: ε = ln (Ht / H0), and the magnitude, i.e positive value, is provided as the result (Grossi et al., 2011) Young's modulus (E) was calculated from compression curves as the initial slope of stress versus strain Hencky strain at fracture (εf) was determined from the first local maximum at the compression curve 2.5 Water binding capacity a) Low salt content Potato starch Carrot fibre No Low c High C No Low p High P s00 s0p s0P sc0 scp scP sC0 sCp sCP b) High salt content Potato starch Carrot fibre No Low c High c No Low p High P S00 Sp0 SP0 S0c Scp SCp Water binding capacity (WBC) was determined by centrifugation, and values were obtained as follows: g of sausage was placed in a 50 ml centrifuge tube with 10 ml of distilled water After homogenization (2 bursts of 10 s) using an Ultra turrax T25 (Janke & Munkel, IKA-Labortechnik), the suspension was centrifuged at 5000 ×g for 10 at 15 °C The supernatant was decanted and the remaining pellet was weighed For all formulation treatments, WBC was determined at least in quadruplets and expressed as percentage of initial weight: S0C WBC % ị ẳ weightstart weightend 100: weightstart A Grossi et al / Meat Science 92 (2012) 481–489 2.6 Protein solubilisation Results and discussion Each of the raw batches (treated at 0.1, 400, 600 and 800 MPa) was homogenized in 0.6 M NaCl (1:4, v/v) at °C The homogenate was centrifuged at 20,000 ×g for 30 and the resulting supernatant was put aside whilst the pellet was re-extracted with ml of 0.6 M NaCl in phosphate buffer (3.38 mM Na2HPO4, 15 mM NaH2PO4; pH 7.5) homogenization solution, stirred for h at °C and centrifuged The two supernatants were then pooled and used for analysis The protein concentration of the solubilised fraction was determined by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) following the method of Laemmli (1970) The samples were dissolved in SDS sample buffer to a protein concentration of mg/ml (106 mM Tris HCl; 141 mM Tris Base; 2% LDS; 10% Glycerol; 0.51 mM EDTA; 0.22 mM SERVA Blue G250; 0.175 mM Phenol Red; pH 8.5) boiled for and loaded onto Tris-acetate gels (Invitrogen, 3–8% polyacrylamide) and stained with 0.1% Coomassie brilliant blue R-250 Following destaining, muscle proteins were identified by comparing relative mobilities to molecular weight standards (Bio-Rad) run under the same conditions 3.1 Meat emulsion characteristics: texture, water binding capacity (WBC), myofibrillar protein solubility and colour 2.7 Napping and ultra flash profiling Sensory assessment by napping and ultra flash profiling (UFP) was performed only on sausages HPP treated at 600 and 800 MPa (400 MPa treated sausages were not sliceable) Sliceability was evaluated by peeling the casings off the cold sausages and slicing a cm sample using a sharp knife Ten sausages were selected for the first set of sensory assessment (Napping 1): S0P, s00, sC0, s0p, and s0P treated at 800 MPa at and 40 °C For the second set (Napping 2) the following sausages were assessed: sCp, scP, and sCP treated at 600 and 800 MPa at and 40 °C Napping, a newer, quick method for sensory assessment (not demanding trained judges), was done in accordance with the principles described by Perrin et al (2008) The samples (slice of sausage) were equilibrated at room temperature for h prior to assessment The samples were simultaneously presented to a panel of 10 sensory assessors, who were requested to distribute the samples on a white A3-paper (40 × 30 cm) according to texture and consistency (assessed by visual inspection, appearance and touch, and texture) Samples positioned close to each other appeared identical and samples appearing different were positioned distant from each other For each sample or group of samples both X co-ordinate and Y co-ordinate were considered Immediately after napping the 10 judges performed UFP They were asked to enrich their A3-paper by writing descriptive words directly on the paper to characterize the samples, which were different or belonged to the same group regarding texture and consistency The profiling words were collected and the most frequent words were chosen 483 Addition of salt (sodium chloride) to processed meat products, during manufacturing is often used to obtain the desired texture as well as the desired water content in the final product One of the most important technological features in the production of processed meat products is to obtain high structural stability and hence high WBC and increased cooking yield It was reported that increasing WBC resulted in increased cooking yield originating from the increase in retained water (Funami, Yada, & Nakao, 1998) The addition of dietary fibre and HPP processing has a positive effect on WBC of processed meat products (Moller et al., 2011) containing 1.8% salt Hence to enable a reduction of salt content in sausages, the effect of addition of ingredients with functional properties and HPP treatment on WBC was determined Sausages with low salt content (s00; 1.2%) had a significantly lower (p b 0.05) WBC than sausages with high salt content (1.8%; S00, S0p, S0P) when HPP treated at °C (Fig 1a) or at 40 °C (Fig 1b) This is in accordance with previous findings (Ruusunen & Puolanne, 2005) where it was suggested that sodium chloride increases the cohesiveness of the batter thereby improving the water retention Salt concentration is also known to affect the solubility of myofibrillar meat proteins like myosin and actin, thereby affecting their ability to form a protein matrix Pressure is known to induce disruption of hydrophobic and electrostatic interactions whilst enhancing 2.8 Statistical analysis Data from the napping and UFP analyses were analysed using Procrustrean Multiple Factor Analysis in the software package R version 2.9.2 (2009-08-24) and the package SensomineR version 1.10 (2009-10-02) with a modified function by Guillaume Le Ray, Delta, Denmark Statistical evaluation of all the data (except napping) was performed using the procedure mixed in SAS (Ver 9.2, SAS Institute Inc., Cary, NC, USA) The mixed procedure was applied to calculate least square means (LSM) and standard error of the means (SE) The statistical model included the fixed effect of HP treatment, fibre content, starch content, salt content and temperature Interactions between fixed effects were only included in the model when significant Differences between fixed effect levels were considered significantly different if p b 0.05 Fig Water binding capacity (WBC) of sausages heat treated at °C (a) and 40 °C (b) Black bars represent sausages HPP at 400 MPa, grey bars at 600 MPa and white bars (800 MPa) For definition of the formulation treatment acronyms, please consult Table 1a and b Error bars represent standard error of the means (SEM) 484 A Grossi et al / Meat Science 92 (2012) 481–489 hydrogen bonding (Mozhaev, Heremans, Frank, Masson, & Balny, 1996) Hence, HPP has been applied to increase the solubility of muscle proteins and hence improve the functional properties of certain myofibrillar proteins (Sikes et al., 2009) On the other hand, it has also been reported that HPP can induce protein denaturation and thereby result in loss of solubility of the main myofibrillar proteins (Lee, Kim, Lee, Hong, & Yamamoto, 2007) It is, thus, important to investigate the effect of HPP treatment and the two salt levels on the protein solubility in the sausages As seen in Fig 2, the different salt concentrations (1.8% or 1.2%) affected the solubility of the myofibrillar proteins in the same manner, and similar marked decreases in the main myofibrillar proteins bands were found Apparently, the HPP effect on protein solubility is superior to the salt effect for the salt levels used in the present study It can be speculated that the reduction of myofibrillar protein bands is a result of denatured proteins forming large molecular weight aggregates (thus not found in the molecular weight separation range of SDS-page gels) or is a result of denatured proteins forming insoluble aggregates (thus lost during the centrifugation step in sample preparation) From these results we can speculate that the differences in WBC are due to salt concentration but also are promoted by the effect of HPP on myofibrillar protein solubility Addition of CF and/or PS to the low salt sausages increased the WBC (Fig 1) However, WBC of sausages with low salt and high PS (Fig 1) did not change significantly between 600 and 800 MPa treatments, whereas sausages with low salt content and high CF showed a significant increase in WBC between 600 and 800 MPa (pb 0.05) This observation can be explained by the fact that insoluble fibre favours water binding properties because water binds to insoluble polysaccharides by hydrogen, ionic and/or hydrophobic interactions (Pietrasik & Janz, 2010) Previously, Moller et al (2011) showed that this phenomenon acts synergistically with the effect of HPP Starch gelatinizes under pressure in two steps, first a hydration of the amorphous parts of the starch granules occurs followed by the swelling and distortion of the crystalline region (Rubens, Snauwaert, Heremans, & Stute, 1999; Simonin, Guyon, Orlowska, de Lamballerie, & Le-Bail, 2011) The WBC results show that the combination of HPP and addition of functional ingredients improves the WBC of low salt sausages to the same level as high salt sausages and hence this technique has technological potential as a tool to produce low salt meat product The instrumental measures of texture are Young's modulus and the strain at fracture Fig shows the modulus of the sausages treated at 400, 600, or 800 MPa at or 40 °C Young's modulus increased with increasing pressure level for all sausages Sausages treated at 800 MPa had about 50% higher modulus value compared to the modulus measured after treatment at 400 MPa (p b 0.05) Texture of sausages containing PS or CF (irrespective of concentration level) was significantly affected (p b 0.05) by pressurization than sausages without PS or CF (S00 and s00) which had the lowest modulus Indeed, the three treatments S00, S0p, and S0P had a high content of salt (1.8%) and differed in the PS content (0, 2, and 3.8%, respectively) and the effect of starch on the Young's modulus value is clear; starch and pressure increased the hardness At the reduced salt content of 1.2% the same texture enhancing effect of starch and pressure is observed (comparing s00 with s0p and s0P in Fig 3) Notably, when the PS level is 3.8% the effect of pressure is similar irrespective of salt level, seen as the same Young's modulus values (comparing S0P, s0P, and sCP in Fig 3a and b) at all treatments (400, 600, and 800 MPa at or 40 °C) The same impact on texture is also observed for sausages with added CF alone (comparing S00 with SC0 and Sc0 and s00 with sC0 and sc0, Fig 3), though sausages with low salt concentration Fig SDS-page electrophoresis of myofibrillar protein extract from sausages high pressure treated at 0.1, 400, 600 and 800 MPa A clear decrease in solubility of the main myofibrillar components is observed after HPP No difference in protein solubility is observed in formulation treatment with high (S) and (s) low salt concentrations S = 1.8% NaCl; s = 1.2% NaCl = indicates neither fibre nor starch and only serves to fill up the code Fig Young's modulus of the sausages (from Table 1) HPP at °C (a) or at 40 °C (b) Black bars represent sausages treated at 400 MPa, grey bars at 600 MPa, and white bars at 800 MPa For definition of the formulation treatment acronyms, please consult Table 1a and b Error bars represent standard error of the means (SEM) A Grossi et al / Meat Science 92 (2012) 481–489 485 Fig Reflectance spectra of the sausages (from Table 1) treated at 800 MPa at 40 °C For definition of the formulation treatment acronyms, please consult Table 1a and b and addition of CF (sC0 and sc0) had lower Young's modulus values than sausages with PS (s0P and s0p) Surprisingly, upon addition of both starch and fibre (independent on concentration levels) no further texture improvement was found, thus there was no synergistic effect of the starch and fibre In general, the magnitude of Young's modulus increased more than two-fold when sausages were treated at 40 °C instead of °C (Fig 3a and b, respectively) This result was expected since myofibrillar protein denaturation is more extensive at moderate high temperature and high pressure compared to the denaturation induced by high pressure treatment alone The high moduli at 40 °C may be explained by a high level of protein denaturation, which promotes protein aggregation and formation of a protein matrix with high gel strength The strain at fracture represents the relative deformation when a material begins to fracture A small strain at fracture indicates that the material is brittle and a high strain at fracture is usually recorded in an elastic material Fig 4a and b shows that the strain at fracture of the sausages increased with increasing pressure at both treatment Fig Hencky strain of sausages heat treated at °C (Fig 3a) and 40 °C (Fig 3b) Black bars represents sausages HPP at 400 MPa, grey bars at 600 MPa and white bars 800 MPa For definition of the formulation treatment acronyms, please consult Table 1a and b Error bars represent standard error of the means (SEM) Table a) L* colour values (average with standard deviation) of sausages either heat treated to a core temperature of or 40 °C and following pressurization at 400, 600 or 800 MPa for For each formulation treatment and high pressure treatment and temperature, different letters represent significant differences (p b 0.05) b) a* colour values (average with standard deviation) of sausages either heat treated to a core temperature of or 40 °C and following pressurization at 400, 600 or 800 MPa for For each formulation treatment and high pressure treatment and temperature, different letters represent significant differences (p b 0.05) P = potato starch (3.8%); p = potato starch (2%); C = carrot fibre (1.5%); c = carrot fibre (0.5%) a) L* values Sausage formulation High salt Low salt 00 Temperature (°C) 40 (°C) HP 400 MPa 600 MPa 800 MPa 400 MPa 600 MPa 800 MPa 0P 63.29 ± 0.11 64.14 ± 0.22 65.02 ± 0.31 65.19 ± 0.15 66.14 ± 0.23 67.64 ± 0.32 a bc bd a ab e 64.55 ± 0.21 65.03 ± 0.27 67.69 ± 0.31 65.98 ± 0.23 67.83 ± 0.31 69.23 ± 0.21 00 b b e ab e f C0 62.72 ± 0.18 63.42 ± 0.22 64.51 ± 0.32 64.52 ± 0.11 65.82 ± 0.28 66.85 ± 0.19 d c b c ab ab 0P Cp cP 64.82 ± 0.32 b 65.10 ± 0.26 bd 67.63 ± 0.3 e 65.62 ± 0.34 a 67.78 ± 0.25 e 68.97 ± 0.18 ef 64.96 ± 0.25 b 64.98 ± 0.22 b 67.80 ± 0.16 e 65.96 ± 0.14 ab 67 87 ± 0.22 e 69.08 ± 0.29 f 64.83 ± 0.27 b 65.22 ± 0.2 bd 67.76 ± 0.24 e 65.83 ± 0.21 ab 68.17 ± 0.19 e 69.17 ± 0.27 f C0 0P Cp cP 6.86 ± 0.08 b 6.46 ± 0.21 c 5.87 ± 0.16 cd 6.15 ± 0.16 b 5.65 ± 0.15 c 4.94 ± 0.18 d 6.70 ± 0.15 6.27 ± 0.13 5.75 ± 0.14 6.25 ± 0.12 5.77 ± 0.13 5.05 ± 0.11 63.87 ± 0.11 64.31 ± 0.24 67.25 ± 0.18 64.47 ± 0.22 66.31 ± 0.28 67.26 ± 0.14 bc b e c ab e b) a* values Sausage formulation High salt Low salt 00 Temperature (°C) 40 (°C) HP 400 MPa 600 MPa 800 MPa 400 MPa 600 MPa 800 MPa 7.56 ± 0.16 6.91 ± 0.13 6.19 ± 0.09 6.86 ± 0.11 6.31 ± 0.18 5.85 ± 0.12 a b c a b c 0P 00 6.68 ± 0.11 b 6.38 ± 0.19 c 5.99 ± 0.13 cd 6.13 ± 0.18 b 5.58 ± 0.17 c 5.13 ± 0.09 d 7.84 ± 0.18 6.93 ± 0.11 6.35 ± 0.11 6.94 ± 0.13 6.53 ± 0.12 6.31 ± 0.17 a b c a b b b c d b c d 6.77 ± 0.14 6.48 ± 0.11 5.55 ± 0.19 6.17 ± 0.05 5.75 ± 0.15 5.15 ± 0.12 b c d b bc d 6.69 ± 0.19 6.22 ± 0.14 5.67 ± 0.21 6.15 ± 0.21 5.61 ± 0.19 5.12 ± 0.11 b c d b c d 486 A Grossi et al / Meat Science 92 (2012) 481–489 temperatures, though for some sausages treated at 40 °C the strain at fracture is lowest at the highest pressure level Especially, sausages with a high content of PS have very low strain at fracture values compared to other sausages, in agreement with the higher modulus values (Fig 3) The strain at fracture is consistent with the Young's modulus (Fig 3), that is a high modulus value represents a hard texture result and a low fracture value indicates a more brittle texture At first sight, colour is one of the main meat product attributes that influence consumer's acceptance Overall, the colour attributes of processed meat products are among others influenced by the meat pigments and meat structural proteins and their degree of denaturation due to processing techniques In comminuted meat products, the colour is also affected by the fat content, size of fat globules, water content, and the homogeneity of the cutting surface of the product (Grossi et al., 2011; Pietrasik & Janz, 2010) Previously we showed that the addition of CF to high fat sausages did not affect the colour of the meat product (Grossi et al., 2011) A general tendency, as seen in Table 2, is that the L* value increases with increasing content of fibre or starch, pressure level, and process temperature This can be explained by water content and matrix changes Addition of CF or PS to the meat emulsion increases Fig (a) Plot from Procrustrean Multiple Factor Analysis of Napping positioning from Napping First dimension explains 46.57% of the variation, second dimension explains 17.27% of the variation Circles indicate significance levels (p b 0.05) (b) Plot from Procrustrean Multiple Factor Analysis of the 11 most used ultra-flash profiling terms First dimension explains 46.57% of the variation, second dimension explains 17.27% of the variation The first number of the codes refers to formulation treatments: 3, high salt with high potato starch content, S0P; 4, low salt with no ingredients, s00; 5, low salt, with high carrot fibre, sC0; 7, low salt and low potato starch, s0p; 8, low salt and high potato starch, s0P The second number in the code is the temperature or 40 °C The third number in the codes is the pressure treatment, 800 MPa A Grossi et al / Meat Science 92 (2012) 481–489 the WBC (Fig.1) and the increased WBC in combination with the added non-meat ingredients (fibre and starch) may have a diluting effect on the meat pigment and structural proteins, thus resulting in more reflected light and a whiter appearance On the contrary, the sausages with low or high salt content and without fibre and starch (S00 and s00 in Table and Fig 1) had the lowest water binding capacity and the lowest lightness values Lightness values increased upon increased pressure level and pressure temperature suggesting an important influence of the matrix changes on lightness of the product Upon pressurization, severe changes in protein conformation take place, and in meat systems especially the changes in pigment and structural proteins will affect the whiteness The impact of conformational or chemical changes of 487 myoglobin on the colour changes is still not clarified Thus, the whitening effect is suggested to result from denaturation of myosin and possible aggregation thereby changing the ability of the meat to absorb and/or reflect light (Supavititpatana & Apichartsrangkoon, 2007) The degree of redness was mainly affected by pressure level and temperature and to a lesser degree by the type and amount of fibre and starch Sausages HPP treated at 800 MPa had a lower a* value than sausages treated at 400 or 600 MPa, and pressurization at 40 °C further decreased the redness Sausages without fibre and starch (S00 and s00) had a significantly higher a* value compared to the other sausages at same pressure and temperature These results suggest that the red colour is more affected by light scattering properties than any pressure-induced changes of myoglobin because redness Fig (a) Plot from Procrustrean Multiple Factor Analysis of Napping® positioning from Napping First dimension explains 58.95% of the variation, second dimension explains 13.39% of the variation Circles indicate significance levels (p b 0.05) (b) Plot from Procrustrean Multiple Factor Analysis of the 13 most used ultra-flash profiling terms First dimension explains 58.95% of the variation, second dimension explains 13.39% of the variation The first number of the codes refers to formulation treatments: 9, low salt with high carrot fibre and low potato starch content, sCp; 10, low salt with low carrot fibre and high potato starch content, scP; 11, low salt, with high carrot fibre and high potato starch content, sCP The second number in the code is the temperature or 40 °C The third number in the codes is the pressure treatment, 600 or 800 MPa 488 A Grossi et al / Meat Science 92 (2012) 481–489 seems to depend on whether the sausages contain hydrocolloids or salt A significant decrease in yellowness (b*) was only found upon pressurization at 600 or 800 MPa at or 40 °C, and is suggested to be involved in the grey–brown colour simultaneously with the lower a* value (Carlez, Veciananogues, & Cheftel, 1995) Fig shows the reflectance curves of pressurized sausages at 800 MPa Usually, the reflectance curve of meat based samples is characterized by the maxima around 540 and 580 nm of oxymyoglobin However, in meat systems containing nitrite salt it is more likely that nitrosomyoglobin is responsible for the red colour The apparent reflectance maximum at 510 nm and minimum at 570 nm seen in the reflectance curve of the sausages (Fig 5) indicate that the red colour corresponds to nitrosylmyochromogen Moreover, as no spectral changes in the reflectance curves (around 500 nm) between non-pressurized and pressurized sausages are observed, it is suggested that it is not related to the severe changes in pigment component (results not shown) As seen in Fig 5, sausages with salt as ingredient (S00 and s00) result in the lowest level of the reflectance curves compared with sausages containing CF and/or PS Interestingly, reducing salt content did not affect the reflectance curve in pressurized sausages in the presence of hydrocolloids like PS and CF Hence, the detected colour changes are probably related to changes in texture, such as denaturation, aggregation of myofibrillar proteins and WBC 3.2 Sensory assessment: napping and ultra flash profiling Fig shows the Napping results of sausages s00, sC0, s0P, s0p, and S0P (Table 1) HPP treated at 800 MPa at or 40 °C Clearly, when the sausages contain PS, the positioning is affected by the temperature at which HPP is performed Thus, sausages containing PS in high (Fig 6, codes and 8) and low (Fig 6, code 7) levels are positioned significantly further to the left at 40 °C compared to °C and to other sausages The UFP analysis showed that those sausages were characterized by being firm and gummy-like, whereas sausages containing PS and HPP treated at °C were characterized by being homogeneous However, all other sausages were characterized by being fatty, floury, creamy, soury, and sticky Notably, reducing the salt content in the sausages with high amounts of PS (Fig 6, codes and 8) did not affect the positioning and the sensory attributes upon HPP treatment at 40 °C, indicating that the salt content was not important for the sensory perception of these sausages Contrary to the fibrerich sausages the treatment temperature did not significantly affect the positioning of sausages containing CF (Fig 6, codes and 5) Hence, it seems from this study that addition of PS results in sausages with a more appealing texture than addition of CF In Napping the sausages containing low salt, a combination of starch and fibre and HPP treated at 600 or 800 MPa at or 40 °C were evaluated It was found that the positioning of the sausages differed significantly according to treatment temperature Thus, HPP at 40 °C resulted in a different texture than at °C This is in agreement with results from Napping 1, since all the samples in Napping contain PS Furthermore, a tendency towards different positioning of sausages HPP treated at 600 MPa compared to 800 MPa was observed (Fig 7) Sausages HPP treated at 40 °C are characterized by being gummy-like, firm, dry, compact and gritty Samples treated at °C are creamy, sticky, slimy, soft, floury, and fatty However, an overall conclusion on the attributes that characterize pressure level in these sausages was not possible This might be due to the fact that the combined effect of mild temperature treatment (40 °C) and HPP (at 600 MPa or 800 MPa) may lead to a higher formation of chemical cross-links and protein denaturation, compared to low temperature treated sausages (5 °C) at both 600 and 800 MPa Conclusion The salt content of pork sausages could be reduced from 1.8 to 1.2% salt by addition of hydrocolloids (either carrot fibres or potato starch) and subsequent HPP at 600 MPa without negative effects on water binding capacity, colour and texture Mild heating (40 °C) acts synergistically with HPP improving even further meat emulsion characteristics Finally, sausages containing potato starch had better sensory quality than the fibre-rich sausages Acknowledgement The authors wish to thank the Danish Ministry of Food, Agriculture and Fisheries for financial support through the projects entitled “New Gourmet pork products obtained through molecular understanding of 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meat gels Food Chemistry, 100, 264–272 Tuomilehto, J., Jousilahti, P., Rastenyte, D., Moltchanov, V., Tanskanen, A., Pietinen, P., et al (2001) Urinary sodium excretion and cardiovascular mortality in Finland: A prospective study The Lancet, 357, 848–851 World Health Organization (2006) Reducing salt intake in population ... results in sausages with a more appealing texture than addition of CF In Napping the sausages containing low salt, a combination of starch and fibre and HPP treated at 600 or 800 MPa at or 40 °C... synergistically with the effect of HPP Starch gelatinizes under pressure in two steps, first a hydration of the amorphous parts of the starch granules occurs followed by the swelling and distortion of the crystalline... production of sausages with reduced salt content by determining the effect of working pressure, temperature, and formulation on the physical properties of pork sausages Materials and methods