Abstract: The study was conducted to optimize the water activity hurdle during the process of development of shelf stable pork sausages using hurdle technology. The humectants used were Skim Milk Powder (SMP) and Textured Soy Protein (TSP). Different parameters evaluated were pH, emulsion stability, cooking yield, moisture, protein and fat contents, water activity, shear force, lovibond tintometer colour scores, texture profiles and sensory attributes. Incorporation of TSP significantly improved the colour and texture profiles of pork sausages, however, above 3% level it adversely affected different sensory attributes especially flavour. Texture profile analysis and sensory evaluation indicated that SMP at 2% level had no adverse effect on the texture of pork sausages. Also, addition of 3% TSP and 2% SMP together had no significant (p>0.05) advantages in improving most of the processing and quality characteristics of pork sausages over 3% TSP addition alone. In both the above treatments the water activity of pork sausages decreased to 0.93 from 0.95.
INTRODUCTION
The microbial safety and stability as well as the sensory and nutritional quality of most foods are based on an application of combined preservation factors called hurdles. More than 60 potential hurdles for foods have been already described and the list of possible hurdles for food preservation is by no means complete (Leistner, 2000). The most important hurdles used in food preservation are temperature (high/low), aw, pH, redox potential and preservatives. The same hurdle could have a positive or a negative effect on foods, depending on its intensity. If the intensity of a particular hurdle in a food is too small, it should be strengthened, if it is detrimental to the food quality it should be lowered. By this adjustment, hurdles in foods can be kept in the optimal range, considering safety as well as quality and thus the total quality of foods.
Water in muscle and meat exist in three forms viz., bound, immobilized and free water, where a major portion is made up of free water. Although it was suspected that the moisture content plays a major role in proliferation of microbes, the exact role is pointing towards the available water. The thermodynamic approach of this influence on the fate of microorganisms in food is termed as activity of water or water activity (aw). aw is a fundamental factor which affects most of the microbial requirements like nutrients, temperature of growth, pH, redox potential etc. is defined as the ratio of water vapour pressure over a food substance to that over pure water at same temperature.
Humectants are the compounds which bind free water and decrease the water activity of a solution or a product. The most effective humectants are sodium chloride (Ledward, 1992) followed by sodium lactate among salts, sucrose (Leistner, 1999) among sugars, glycerol polyethylene glycol 200, 400 and 600 among polyols (Prabhakar and Ramamurthi, 1990). Their use in meat products is limited due to adverse effects on both health and sensory qualities when used in large amounts. Alternatively, soy protein, protein hydrolysates (Ledward, 1985), skim milk powder, milk protein coprecipitate (Lerici et al., 1983) were used without affecting the sensory qualities and health. . suggested that products in the vicinity of aw 0.92 were more preferred by the panelists than those with lower aw levels. This finding was further confirmed by Karthikeyan et al. (2000) in hurdle treated goat meat keema.
SMP, often referred as non-fat dry milk, is used as a functional ingredient in a variety of comminuted meat products. It contains casein, whey protein, lactose, minerals and a small amount of fat and water. The efficiency of SMP in stabilization of meat emulsions depends on the ratio at which they are mixed and the extent of protein-protein interactions (Hayes et al., 2006). Also, dehydrated TSP granules (52.4% protein) could be used in comminuted meat products as a binder for improving yields, as a humectant to reduce water activity, as a gelling agent to enhance emulsion stability and for meat replacement to reduce costs (Das et al., 2006). In this study skim milk powder and textured soy protein were evaluated as humectants to develop shelf stable pork sausages. The objective of the present study was to standardize the optimum level of humectants (i.e., aw hurdle) for processing shelf stable pork sausages skim milk powder and textured soy protein.
MATERIALS AND METHODS
Lean Pork and Pork Fat
Lean pork and fat (back fat) required for the experiments were obtained
from crossbred barrows (75% Landracex25% Desi) (60-70 kg live weight)
slaughtered as per standard procedure at the experimental abattoir of
Livestock Products Technology Division, Indian Veterinary Research Institute,
Izatnagar. Meat (about 3 kg in each batch) and fat were obtained from
ham portion of the carcass within 0.5 h of slaughter and deboning was
done in the processing plant after conditioning in a refrigerator at 4±1°C
for about 16 h. Additional back fat was obtained from loin portion, if
required. Skin, fat and meat were separated manually. Meat was cut into
cubes of about 3 cm and ground using 13 mm followed by 8 mm plates in
a Seydelmann meat grinder (model WD 114, Stutgart, Germany). Fat was ground
using 13 mm followed by 3 mm plates in the same grinder. Ground meat and
fat were packaged in LDPE bags and kept frozen (-18±1°C) till
subsequent use. Frozen meat and fat were thawed at 4±1°C for
16 h before use.
Processing of Pork Sausages
Meat emulsion was prepared using Seydelmann food cutter (Model K20 Ras,
Stutgart, Germany) as per the procedure mentioned hereunder with 20% pork
fat. About 4 kg batches were made, namely, 2600 g lean pork, 800 g pork
fat, 200 g condiments mix and refined wheat flour each, 80 g spices mix
and refined salt each and 20 g cane sugar and sodium tripoly phosphate
each. Also, sodium nitrite was added at 0.015%. Spice mix was prepared
as per the formulation developed in the laboratory. Onion and garlic were
used in the ratio 3:1 as condiments. To the ground lean pork, salt, sugar,
sodium nitrite and sodium tripoly phosphate were added and chopped for
about 2 min. Condiments mix was then added and chopped again for 2 min
(water/ice flakes were not added to reduce the water activity in the sausages).
Ground pork fat was slowly incorporated while chopping which was continued
till the fat was completely dispersed in the batter (3-4 min). Spice mix
and refined wheat flour were added and chopping was continued for another
1 min to get a fine viscous emulsion. pH of different batches of emulsion
was then adjusted to ~ 5.90 using 0.5 N lactic acid and glucono-delta-lactone
(0.1%) (The pH hurdle was standardized by conducting several preliminary
trials in the laboratory). The temperature of the emulsion varied from
10-12°C.
Experiment 1
About 4 kg meat emulsion was prepared as per the formulation mentioned
above. The emulsion was divided into 4 equal batches and the first batch
served as control. In the remaining 3 batches commercially available SMP
(about 35% protein) was used at 1, 2 and 3% levels in the formulation,
i.e., over and above 100% levels, as a humectant, which was added slowly
to the respective emulsions while blending for 1 min in a small Hobart
food cutter (Model N-50 G, Troy, Ohio, USA). Meat emulsions were then
stuffed into 25 mm diameter cellulose casings (Viskase Nojax, Viskase
Co. Inc., Chicago, USA) using hydraulic sausage filler (Mainca, Model
EP-25, Spain) and linked manually at about 12 cm intervals. Cooking was
done in a steam oven without pressure till the internal temperature reaches
75°C, as recorded by a digital probe thermometer (Model CT-809, Century
Instruments (P) Ltd., Chandigarh). The sausages were cooled to room temperature
and peeled off the casings.
Experiment 2
About 4 kg meat emulsion was prepared as per the formulation mentioned
above. The emulsion was divided into 4 equal batches and the first batch
served as control. Commercially available dehydrated TSP granules (52.4%
protein) were powdered in a mixer and added in the formulation at 3, 4
and 5% levels i.e., over and above 100% level. The emulsions were processed
into sausages as mentioned in Experiment 1.
Experiment 3
About 4 kg meat emulsion was prepared as per the formulation mentioned
above. The emulsion was divided into 4 equal batches and the first batch
served as control. Powdered TSP and SMP were added alone and in combination
at the levels selected from the above experiments to adjust the aw
of the sausages to a desirable level. Different treatments evaluated were
1. Control (without TSP and SMP) 2. Treatment 1 -2% SMP, 3. Treatment
2 -3% TSP and 4. Treatment 3 -2% SMP + 3% TSP. Different levels of TSP
and SMP added were over and above 100% in the base formulation. The emulsions
were processed into sausages as mentioned in Experiment 1.
pH was determined using a digital pH meter (Elico, Model LI 127, India). The weight of sausages was recorded before and after initial cooking and the yield was calculated (cooking yield = weight of cooked sausages/weight of raw sausagesx 100) and expressed as percentage. The procedure of Kondaiah et al. (1985) was followed to measure the emulsion stability. Moisture, fat and protein contents of the sausages were determined as per standard procedures (AOAC, 1995). The water activity (aw) of the sausages was measured by Paw kit water activity meter (Decagon, Devices, USA). The colour of the cooked pork sausages were measured using a Lovibond Tintometer (Model F, Greenwich, UK). Samples from 3 different places of sausages were taken in the sample holder and secured against the viewing aperture. The sample colour was matched by adjusting red (a) and yellow (b) units, while keeping the blue units fixed at 2.0. The corresponding colour units were recorded. The hue and chroma values were determined by using the formula, (tan-1)b/a (Little, 1975) and (a2 + b2)1/2 (Froehlich et al., 1983) respectively, where a = red unit, b = yellow unit.
Texture Profile Analysis (TPA) of pork sausages was conducted as per the procedure described earlier (Bourne, 1978) using a Stable Microsystems Texturometer (Stable Microsystems Ltd., Surrey, UK) model TA-XT2 texture analyzer attached to a software, texture expert. The texturometer was also used to measure shear force and work of shearing using a Warner-Bratzler blade.
Standard sensory evaluation method using 8-point descriptive scale (Keeton, 1983) was followed with modifications where 8 = excellent; 1 = extremely poor. The experienced panel (7 members) consisted of scientists and post-graduate students of Division of Livestock Products Technology, IVRI, Izatnagar. Pork sausages were warmed (40-45°C) using microwave oven for 1 min and served to the panelists. Sensory evaluations were conducted between 3.30-4 pm and filtered tap water was provided to the panelists for rinsing their mouth in between evaluation of different samples.
The experiments were replicated a minimum of three times and the data generated for different quality characteristics were compiled and analyzed using randomized block design at the institutes computer center. The data were subjected to analysis of variance (one way ANOVA), least significant difference (Snedecor and Cochran, 1995) and Duncan’s multiple range tests (Steel and Torris, 1981) for comparing the means to find the effects between treatments for various parameters in different experiments. The smallest difference (D5%) for two means to be significantly different (p<0.05) is reported.
RESULTS AND DISCUSSION
Experiment 1
Physico-Chemical Characteristics
Addition of 2 and 3% SMP significantly increased (p<0.01) the emulsion
pH, while the pH of cooked sausages was significantly higher only in products
with 3% SMP (Table 1). Incorporation of 5% SMP in chicken
sausages was found to increase the pH significantly (Anjaneyulu et
al., 1996). Emulsion Stability (ES) and Cooking Yield (CY) were significantly
higher in sausages containing 2 and 3% SMP compared to control and this
could be attributed to the better moisture and fat retention in sausages
containing SMP. Girish et al. (2004) reported that addition of
3% SMP to chicken patties increased the yield of the product. Similarly,
Zorba et al. (2005) observed that addition of 0.5% SMP improved
the stability of meat emulsions prepared with beef, chicken and turkey
meats. Moisture, protein and fat contents of the sausages increased markedly
at all levels of SMP addition than control, but a significant increase
in these parameters was observed only at 2 and 3% levels. This suggests
that SMP acted as a binder and improved the water and fat binding properties
in the sausages. Similar observations were also reported by Hung and Zayas
(1992) and Hayes et al. (2006). Shear force and work of shearing
increased significantly in sausages containing 2 and 3% SMP which could
be due to the better binding properties resulted from SMP addition.
Sausages with 1 and 2% SMP had similar redness (a-values) as that of control while at 3% level, redness was reduced significantly (Table 1). A linear increase in yellowness (b-value) and hue angle was observed with increasing levels of SMP in sausages. Chroma, which measures the saturation of colour, increased with increase in SMP level, but no significant difference (p>0.05) was observed for this parameter between the sausages containing 2 and 3% SMP. The reduction in redness and increase in yellowness of sausages could be due to the replacement of lean content by SMP and subsequent dilution of meat pigments (Rocha-Garza and Zayas, 1996). Addition of 5% SMP was found to increase the yellowness of pork sausages significantly (Baardseth et al., 1992).
Hardness increased up to 2% level, while incorporation of 3% SMP slightly reduced the hardness of sausages which could be due to the lower cohesiveness observed in the sausages with 3% SMP (Table 1). Springiness was reduced significantly with increasing levels of SMP in the sausages which might be due to the reduction in elasticity in sausages containing SMP. Changes in gumminess and chewiness were similar to that in hardness, because these parameters are mostly determined by hardness and cohesiveness of the products. The available literature shows conflicting reports on the effect of SMP on the texture profiles of meat products. Hung and Zayas (1992) indicated significant improvement in frankfurters, while Cserhalmi-ormai and Czukor (1991) reported a negative effect of SMP on the firmness of sausages. The latter also observed less springiness but improved cohesiveness in sausages containing SMP.
Sensory Evaluation
There was significant improvement (p<0.01) in the appearance and flavour
of the sausages by the addition of SMP (Table 1). Appearance
scores for sausages containing 3% SMP was significantly higher than all
other treatments. However, Hung and Zayas
(1992) did not notice any difference
in terms of appearance of frankfurters added with SMP. Panelists had markedly
higher liking for the flavour of sausages containing SMP especially at
2 and 3% levels and it could be due to the presence of lactose in SMP
which act as a flavour enhancer. Juiciness of sausages containing SMP
was comparable to that of control. Products with 2% SMP had better texture
than those with 3% SMP and the finding was in agreement with the results
of instrumental texture profile analysis, where lower hardness and cohesiveness
were observed in sausages with 3% SMP compared to the one with 2% SMP.
Binding of sausages was not affected by incorporation of SMP. Chicken
sausages containing SMP were reported to have better flavour, texture
and juiciness than control (Anjaneyulu et al., 1996). Overall acceptability
of the sausages increased with incorporation of SMP at 2 and 3%. Addition
of SMP at 1.5% level (Ellekjaer et al., 1996) and at 2 and 3% levels
(Girish et al., 2004) was found to improve the overall acceptability
of the pork sausages and chicken patties respectively.
| Table 1: | Effect of different levels of Skim Milk Powder (SMP) on the quality of pork sausages |
n = 9; #n = 3; *n = 21, Based on 8-point
descriptive scale; Means with different superscripts in the same row
indicate significant difference (p<0.05) |
|
Experiment 2
Physico-Chemical Characteristics
The addition of TSP significantly increased (p<0.01) the pH of emulsion
and cooked sausages (Table 2). Addition of 3% TSP in
the formulation increased the pH of emulsion by 0.04 units while addition
of 5% TSP increased it by 0.1 unit which was expected due to higher pH
of TSP granules (6.8-7.0). A similar observation was reported by Das et
al. (2006) in goat meat patties with textured soy proteins. Also,
an increase of pH by incorporation of isolated soy protein was observed
in frankfurters (Decker et al., 1986) and in low fat bologna (Chin
et al., 1999). Emulsion stability, an index of loss of water, fat
and solids from a meat emulsion on heating, increased significantly (p<0.01)
with incorporation of TSP. As expected cooking yield also showed the same
trend, but a significant difference was absent (p>0.05) for CY between
sausages containing 4 and 5% TSP. Soy protein was reported to act as an
emulsifier and fat encapsulating agent by supplementing myosin and actomyosin
and thereby prevent fat and water separation while cooking (Reichet, 1991).
The stabilizing effect of soy proteins in the emulsion is related to high
electric charge and more hydrophilic-lipophilic groups within the protein
structure that increase the protein-lipid and protein-water interactions
(Pena-Ramos and Xiong, 2003). They form charged layer around fat droplets
causing natural repulsion, reducing interfacial tension and thus prevent
coalescence (Alamanou et al., 1996). The beneficial effect of different
forms of soy proteins on emulsifying properties was reported in various
meat products like chorizos (Porcella et al., 2001), pork patties
(Pena-Ramos and Xiong, 2003) and in goat meat patties (Das et al.,
2006).
| Table 2: | Effect of different levels of Textured Soy Protein (TSP) on the quality of pork sausages |
n = 9, #n = 3; *n = 21, Based on 8-point
descriptive scale; Means with different superscripts in the same row
indicate significant difference (p<0.05) |
|
Moisture and fat content of sausages were increased which could be due to increase in hydrophilic and lipophilic groups that increase the protein-lipid and protein-water interactions (Pena-Ramos and Xiong, 2003). Addition of TSP significantly increased (p<0.01) the protein content in sausages which might be due to the higher protein content of TSP. A significant increase in protein content due to incorporation of soy proteins was reported for low fat bologna (Chin et al., 1999) and in vacuum packaged chorizos (Porcella et al., 2001).
Addition of TSP at 3% level significantly increased (p<0.01) the shear force and work of shearing of the sausages (Table 2). This might be due to the better binding properties resulted from increased protein content by the addition of TSP. However, addition at 4 or 5% level had found no further significant advantage (p>0.05) over the 3% level on these parameters. Water activity of sausages was significantly decreased (p<0.01) by the addition of TSP. Incorporation of 3% TSP reduced the aw by 0.02 units and 5% decreased it by 0.03 units while addition of 4% TSP had found no advantage over 3% level in reducing the aw of the sausages. The reduction in aw, despite a higher moisture retention might be due to the addition of TSP in the dehydrated powder form. Moreover, the effect of increased moisture retention in the products might have counter balanced by an increase in fat retention. Instances of significant reduction in aw of the products with increasing levels of humectants are reported (Fernandez-Salguero et al., 1994). However, Das et al. (2006) observed a non-significant (p>0.05) effect of TSP addition on the aw of the goat meat patties, which might be due to the addition of TSP after hydration (1:2.75 w/w) by these authors.
Colour is an important parameter in cooked meat products because consumers associate their preference to a bright pink colour of the product (Bryhni et al., 2003). Addition of TSP in the formulation significantly lowered (p<0.01) the redness (a-value) while increased yellowness (b-values), hue angle and chroma, which measures the saturation of colour, of the sausages (Table 2). However, the redness of the sausages containing 3% TSP was comparable with that of control. The effect of 3, 4 or 5% level of TSP on lovibond colour units of sausages did also differ significantly among themselves. The reduction in redness and increase in yellowness was attributed to replacement of lean content and the consequent dilution of meat pigments (Rocha-Garza and Zayas, 1996). Chin et al. (1999) reported that replacement of 4% meat protein with soy protein isolate increased lightness and yellowness and decreased redness. Recently, Das et al. (2006) reported that addition of hydrated soy granules to goat meat patties significantly decreased the redness (a-value) and increased yellowness (b-values).
Addition of TSP significantly (p<0.01) affected all the texture profiles of pork sausages and the effect was more pronounced with increasing levels of TSP in the product (Table 2). Hardness was significantly decreased by adding TSP at 5% level compared to TSP at 4% level which could be due to the reduction in cohesiveness of the product as evident from the texture analysis. Chin et al. (1999) reported that low fat bologna sausages formulated with 0 and 2.2% soy protein isolate had similar hardness values but the addition at 4.4% level decreased the hardness. The higher springiness observed in sausages with 4 and 5% TSP might be due to an increase in elasticity of the products by TSP addition at higher levels. The significantly higher (p<0.01) gumminess and chewiness observed in sausages with TSP could be due to the formation of better quality emulsion as a result of increase in protein content of the formulation. Matulis et al. (1995) observed that soy protein addition increased hardness but decreased cohesiveness and juiciness. The authors concluded that more than 3% soy protein should not be incorporated in low-fat frankfurters.
Sensory Evaluation
Incorporation of TSP markedly affected all the sensory attributes
of the pork sausages and the effect was more distinct at higher levels
(Table 2). Sausages with 3% TSP had similar appearance
as control while 4 and 5% levels resulted in significant reduction (p<0.01)
of appearance which suggest that panelists had less liking for the increased
yellowness in products with higher levels of TSP. Flavour scores were
significantly decreased (p<0.01) with increase of TSP level in the
formulation. Panelists were able to detect a mild beany flavour in sausages
even at 3% level while at 4 and 5% levels beany flavour intensity was
found high. Incorporation of higher levels of TSP significantly decreased
the flavour and colour scores in ground beef patties (Deliza et al.,
2002) and in goat meat patties (Das et al., 2006). The reduction
in juiciness observed with higher levels of TSP was due to increased dryness
in products as a result of incorporation of dehydrated powdered TSP. The
texture scores were in agreement with that of instrumental hardness values.
Even though, a reduction in cohesiveness at 5% TSP level was observed
in instrumental texture analysis, panelists were unable to detect the
same, as evident from the binding scores. Panelists liked the texture
of sausages with 3 and 4% TSP even more than that of control sausages.
The results indicated that the overall acceptability of sausages was mostly
influenced by their flavour and texture properties. Even though panelists
detected mild beany flavour in sausages with 3% TSP, the better textural
characteristics resulted in their higher overall acceptability by the
panelists. Similar effects of soy proteins above 3% level on sensory attributes
were also reported in frankfurters (Matulis et al. 1995) and in
vacuum packaged chorizos (Porcella et al., 2001).
| Table 3: | Effect of combination of TSP and SMP on the quality of pork sausages |
n = 9; #n = 3; *n = 21, Based on 8-point
descriptive scale; Means with different superscripts in the same row
indicate significant difference (p<0.05) |
|
Experiment 3
Physico-Chemical Characteristics
Addition of TSP and SMP alone and in combination increased the emulsion
pH significantly (p<0.05) (Table 3). Maximum increase
in emulsion pH (0.07 units) was observed for combination while the least
for TSP. pH of cooked sausages did not differ significantly (p>0.05)
among different treatments. However, an increase in product pH with incorporation
of TSP in goat meat patties (Das et al., 2006) and SMP in chicken
sausages (Anjaneyulu et al., 1996) were reported. ES was significantly
higher for treatments 2 and 3 compared to treatment 1, while control had
the lowest ES. CY did not differ significantly among treatments but was
significantly higher than that of control. Markedly higher ES and CY in
sausages from treatments 2 and 3 could be attributed to the better emulsifying
properties of TSP. Soy protein was reported to act as an emulsifier and
fat encapsulating agent by supplementing myosin and actomyosin and thereby
prevent fat and water separation during cooking (Reichet, 1991). SMP was
also found to improve the stability of meat emulsions prepared with beef,
chicken and turkey meat (Zorba et al., 2005) and this could be
attributed to the higher ES and CY observed in treatment 1 compared to
control. However, the results indicated that incorporation of 3% TSP alone
or in combination with 2% SMP resulted in better emulsifying properties
in the meat system than addition of 2% SMP alone. Soy proteins were found
to improve the emulsifying properties in chorizos (Porcella et al.,
2001) and in pork patties (Pena-Ramos and Xiong, 2003) while Zorba et
al. (2005) reported addition of SMP was improved the stability of
different meat emulsions.
Addition of 2% SMP and 3% TSP alone or in combination significantly increased the moisture, protein and fat contents of pork sausages and the effect was more distinct in sausages from treatments 2 and 3 compared to those from treatment 1. This suggest that TSP is having better water and fat binding properties in meat systems than SMP, which could be attributed to the higher protein content of TSP (53% vs 35%). A significant increase in protein content in low fat bologna due to incorporation of soy proteins was reported (Chin et al., 1999) while Girish et al. (2004) reported that addition of 2% SMP increased moisture, protein and fat contents of chicken patties compared to control.
Shear force was significantly higher (P<0.01) for sausages from treatments 2 and 3 and those from treatment 3 had more work of shearing than those from treatment 2. This indicates that addition of TSP and SMP together resulted in better binding of pork sausages than when they were added alone. The comparatively higher shear force observed in sausages from treatments 2 and 3 might be attributed to their higher protein content. Incorporation of 3% TSP reduced aw by 0.02 units while combining it with 2% SMP had found no additional advantage in reducing the aw. Fernandez-Salguero et al. (1994) also reported reduction in aw of intermediate moisture meat products with addition of different humectants.
Lovibond tintometer colour units of the pork sausages were significantly influenced by the addition of SMP and/or TSP. Sausages from treatments 2 and 3 had significantly lower redness (a-values) while their yellowness (b-values) was significantly higher than other treatments. Addition of 2% SMP did not affect the redness of the sausages while it increased their yellowness significantly. The reduction in redness and increase in yellowness in sausages resulted from incorporation of TSP and/or SMP was attributed to replacement of lean content and the consequent dilution of meat proteins (Rocha-Garza and Zayas, 1996). Das et al. (2006) reported that addition of hydrated soy granules to goat meat patties significantly decreased the redness and increased yellowness. Similarly, Baardseth et al. (1992) found that addition of 5% SMP increased the yellowness of pork sausages significantly.
Instrumental texture profiles of the pork sausages were markedly affected by the addition of TSP and/or SMP (Table 3). Hardness was significantly higher (p<0.01) for sausages containing TSP alone or in combination with SMP, which reiterates the observations for ES and shear force. Even though sausages from treatment 3 had slightly higher values, they did not differ significantly (p>0.05) from those of treatment 2 for springiness, cohesiveness, gumminess and chewiness. Both treatments 2 and 3 had significantly higher values for most of the texture profiles than treatment 1, however, the latter also shown significantly better values compared to control. Adhesiveness showed inconsistent readings among different treatments. These findings indicated that addition of 3% TSP alone or in combination with 2% SMP resulted in better textural characteristics of pork sausages than those with 2% SMP or control. The comparatively better texture profiles of sausages from treatments 2 and 3 could be attributed to the good emulsifying properties resulted from an increase in the protein content in the formulation. A similar improvement in different texture profiles of comminuted meat products by TSP over SMP was also reported (Muguruma et al., 2003).
Sensory Evaluation
Use of a combination of 3% TSP and 2% SMP had no additional advantage
over addition of 3% TSP alone for colour and flavour of pork sausages
(Table 3). However, the sausages containing both TSP
and SMP had slightly higher juiciness and texture than those with TSP
alone. The results also showed that addition of 3% TSP alone or in combination
with 2% SMP had significantly improved all the sensory attributes of the
sausages compared to those containing only 2% SMP. The higher flavour,
juiciness and texture scores observed in sausages containing TSP could
be due to the better retention of fat and/or moisture by TSP in these
products. The sensory texture scores were in agreement with that of instrumental
shear force and hardness values. Overall acceptability scores indicated
that panelists had slightly higher liking for the sausages containing
3% TSP and 2% SMP compared to those with 3% TSP alone. It also showed
that addition of 2% SMP alone could not have much influence on any of
the sensory attributes of pork sausages. The literature shows that incorporation
of TSP and/or SMP to different meat products resulted in better sensory
attributes in these products, especially flavour and texture (Matulis
et al., 1995; Deliza et al., 2002 for TSP and Anjaneyulu
et al., 1996; Girish et al., 2004 for SMP).
CONCLUSIONS
Incorporation of SMP above 2% and TSP above 3% levels in the formulation had adverse effect on different physico-chemical and sensory attributes. Also, addition of 3% TSP and 2% SMP together had no significant advantages in improving most of the processing and quality characteristics of pork sausages over 3% TSP addition alone. Both the above treatments had similar water activity. The sensory panelists also did not find any significant difference among the treatments 2 and 3. However, we were not able to reduce the aw of the products to low levels, because addition of humectants above the selected levels were found to influence the different quality and sensory characteristics of the sausages adversely. The sensory panelists indicated that the sausages developed with 0.93 aw had similar characteristics of a fresh sausage.
ACKNOWLEDGMENT
The authors acknowledge the financial assistance in the form of Senior Research Fellowship by Director, Indian Veterinary Research Institute.