MORTADELLA SAUSAGE PRODUCED WITH SOYBEAN OIL INSTEAD OF PORK FAT

Headnote

ABSTRACT

This study examines the effects of partially or completely replacing pork backfat with soybean oil in mortadella production. Mortadella sausages of various formulations showed no differences (P > 0.05) in any of the technological and physico-chemical parameters evaluated (process yield, shear force, pH, water activity and proximate composition). When compared to products made with pork backfat, those made with vegetable oil had a higher unsaturated fatty acid content (P < 0.05) and a similar cholesterol content (P > 0.05). Products made with vegetable oil scored lower (P < 0.05) than those made with pork fat on all of the evaluated sensory attributes (colour, odour, flavour, texture and overall acceptability).

- Key words: Sausage, soybean oil, fatty acids, sensory evaluation -

INTRODUCTION

High dietary intakes of saturated fatty acids increase total cholesterol and LDL cholesterol. In the treatment of hypercholesterolemia, patients are advised to reduce their dietary consumption of saturated fat. Animal fats (except those from fish), palm and coconut oils are rich in saturated fatty acids. It is therefore advisable to limit the consumption of these fats, particularly animal fat in fatty meats and sausages. Dietary cholesterol increases blood cholesterol in several animal species, including humans. Replacing saturated fatty acids with polyunsaturated fatty acids reduces total cholesterol and blood LDL (SOCESP, 2006). The American Heart Association recommends a daily intake of 300 mg of cholesterol for humans (AHA, 2009). Oleic and linoleic acids increase HDL (good cholesterol) and decrease LDL (PEREIRA et al, 2000).

Soybean oil is very rich in polyunsaturated fatty acids, particularly linoleic acid (55.62%). It also has the highest PUFA percentage of any oil (59.70%, compared to 30.08% for canola oil) and the largest PUFA/ SFA ratio (MAIA et al, 2006). According to the Brazilian Association of Vegetable Oil Industries (ABIOVE, 2009), Brazil produces about 28% of the world's supply of soybeans, with the 2006 harvest estimated to be 57 million tons. Brazil is the second-largest world producer and exporter of soybeans, soy meal and soybean oil. In 2008, Brazil produced 6.19 million tons of soybean oil. There are several advantages to replacing animal fat with soybean oil in meat products; soybean oil can be produced in large volumes and is healthier like olive, corn and sunflower oils. Soybean oil is also a relatively inexpensive alternative to animal fat; the price of soybean oil in Brazil is almost half the price of pork backfat (weight by weight).

Meat products such as hamburgers, mortadella and salami are popular with consumers and are a major market for the sector industries. Their consumption is affected by many factors, including the product's sensory and nutritional characteristics, safety, price and convenience (JIMENEZ-COLMENERO et al, 2001). The relatively high cholesterol content and low ratio of polyunsaturated to saturated fatty acids (PUFA/ SFA) presented by animal fats play a negative role in the development of several diseases, including coronary artery disease. Pork lard, the main source of animal fat used in the development of sausages, contains 38% saturated fatty acids, while soybean oil contains only 16% saturated fatty acids (MAIA et al, 2006; BRAGAGNOLO and RODRIGUEZ-AMAYA, 2002).

Mortadella, one of the most commonly consumed meat products, is produced from a meat emulsion that may contain pork backfat and other ingrethents. This emulsion is wrapped in natural or artificial casings, shaped and submitted to appropriate heat treatment (BRAZIL, 2000). Animal fat may be primarily responsible for the development of an acceptable aroma, taste, texture and succulence in meat products. YILMAZ et al (2002) replaced animal fat with sunflower oil and found significant differences in texture, odour and succulence, but not in flavour. However, HSU and YU (2002) showed that replacing animal fat with vegetable oils from various sources did not significantly change the texture, colour, odour, flavour and acceptability of meatballs.

The objective of this study was to evaluate the nutritional, technological and sensory characteristics of mortadella sausages produced with soybean oil instead of the traditional pork backfat.

MATERIALS AND METHODS

Sausage manufacture

Three types of mortadella were produced: a "Pork" formulation made with 100% pork backfat; a "50/50" formulation made with 50% pork backfat and 50% soybean oil; and an "Oil" formulation made with 100% soybean oil.

The raw animal materials included beef meat that had been cleaned of excess fat and collagen and pork backfat that had been skinned, ground and homogenised before freezing. Commercial soybean oil (Liza brand) was used. The levels of protein, lipid and moisture of the meat and pork backfat were determined, and the vegetable oil composition was considered to be 100% fat. Based on the composition of the raw materials, each of the three formulations was developed to ensure equal levels of protein (12,5%) and fat (15%) and a moisture to protein ratio of 5:1. Two batches (two replicates) of 15 kg were processed for each treatment. Table 1 shows each of the three formulations used in the first replication of the experiment. Other ingredients used in identical proportions in all of the treatments included: 1.5% mortadella seasoning mix (Aglomix S 1 00-T - DiCARNE) containing an antioxidant (sodium erythorbate) and emulsifler (sodium polyphosphate); 1.6% table salt (Cisne); 0.35% cure salt (Standard, DiCARNE); 1% isolated soy protein (Supro 500L - Solae); 0.5% crushed garlic; 0. 1% ground white pepper; and 0.1% monosodium glutamate (Ajinomoto). A combination of starch was also used in a ratio of 1.5% OSA starch (RD 474(TM)) to 3.5% waxy maize starch (AMISOL(TM) 4000); both starches were obtained from Corn Products, Added fat and/or oil was homogenised with the meat and other ingrethents in a cutter for approximately 10 minutes according to the following procedure: the meat (at an initial temperature of around 1°C) was combined with the regular salt, cure salt and seasoning mix and comminuted for two minutes. Next, half of the ice was added; after one minute, the vegetable oil and/or pork fat was added. The fat was added directly, which means that neither the oil nor the pork fat was pre-emulsified. The mass was then chopped for two minutes, and the isolated soy protein was added. After one additional minute, the rest of the ice was added. The mass was chopped for one more minute and the starches were added. Finally, the entire mass was chopped for about two minutes and was removed with a temperature of around 14°C. The emulsion was stuffed into 70 mm diameter cellulosic casings; each unit was approximately 500 g. The mortadellas were heat-processed in a smokehouse for about 4 hours until the internal temperature of the coolest product reached 72°C. Temperature was measured with thermocouples placed in the centre of three sausages located in different areas of the smokehouse. The temperature of the smokehouse varied from an initial 55° to 85°C at the end of the cooking process. After they were cooked, the mortadellas were cooled in a cold water shower, vacuum packed and stored at 00C (±1°C) until analysis. The sausages were analysed between five and seven days after they were processed. The sausages were kept under vacuum to avoid dehydration during cold storage that can result from the use of cellulosic casing that are permeable to water vapour. This method of packaging (cellulosic casing plus vacuum storage) is also used by the leading commercial mortadella producer in Brazil.

Physical and chemical determinations

The official AOAC methodology (CUNNIF, 1998) was used to determine moisture, protein, lipid and ash contents. These determinations were made in triplicate for each treatment.

Two tests were conducted to characterise the texture of the products; both tests used a texturometer (TA.XT2i, SMS) at 25°C. Ten cylinders of each treatment were tested as follows:

- To measure hardness (compression strength: maximum force required to compress the samples), the products were cut into 20x20 mm cylinders and submitted to compression tests with a 20 mm cylindrical probe moving at 500 mm/ min until 50% deformation was achieved.

- To measure tenderness (shear force: maximum force required to shear the samples on their round surface), the products were cut into cylinders with a diameter of 14 mm and a height of 20 mm and sheared with a Warner-Bratzler probe moving at a speed of 500 mm/min.

- To calculate the process yield, stuffed mortadellas were weighed before they entered the smokehouse and immediately after they were cooked and cooled. The yield was calculated using the following equation: Yield (%) = (final weight / initial weight) x 100.

- To assess water activity, mortadellas were crushed and homogenised. Water activity was measured by means of the Aqualab apparatus (Series 3TE) at 25°C. This analysis was performed in triplicate for each treatment.

- To determine pH values, the electrode of a portable pH meter (model F- 1002) was immersed in a solution created with 200 g of mortadella sample per litre of water.

Fatty acid composition and cholesterol determination

A three-stage process was used to determine the fatty acid composition. Lipid extraction was performed using the method described by FOLCH etal (1957), and fatty acid esterification was performed using the method described by HARTMAN and LAGO (1973). Finally, gas chromatography was performed. The hexanic fraction containing the esters was analysed in a gas Chromatograph (HP 5890 Series II) equipped with a capillary column (DB-23 from Agilent) with dimensions of 60 m x 0.25 mm x 0,25 µm; the capillary column was coupled to a flame ionisation detector. The gas flow included 1 mL/ min of helium, 10 mL/min of hydrogen and 100 mL/min of air. The following temperature grathent was used: 130°C for 1 minute, from 130° to 170°C at 6.5°C/min, from 170° to 215°C at 2.8°C/min, 215°C for 12 minutes, from 215° to 230°C at 40°C/min, and 230°C for 3 minutes. The temperature in the injector was 270°C and the temperature in the detector was 280°C. Saturated and unsaturated fatty acids with 6, 8, 10, 12, 14, 15, 16 (eis and trans), 17, 18 (eis and trans), 20, 22 and 24 carbon atoms were analysed through comparison with data obtained from the GC authentic standards (SUPELCO - Catalog. No 18920- IAMP) that were methylated and eluted under the same conditions. The calculations were made by a computer coupled to the gaschromatograph using the GC Solution software.

Cholesterol content was determined in two stages. Cholesterol was first extracted and then submitted to high-performance liquid chromatography (HPLC). The analysis was conducted, with some adjustments, according to the method described by SALDANHA et al (2004). For the cholesterol extraction, 2 g of KOH and 50 mL of alcohol were added to 2 g of the homogenised sample. Flasks containing this solution were placed in a water bath at 90°C for 30 minutes and then cooled under running water and ice; 50 mL of distilled water were added. The solution was transferred to a separation funnel and 20 mL of hexane were added. The funnels were agitated and left to rest until phase separation. The lower phase was collected in another separation with the addition of hexane and was discarded. The collected solutions (hexane phases) were washed with distilled water. The filtrate was evaporated, first in a water bath at 900C and then with N2. A liquid Chromatograph (SHIMADZU) with a photodiode array detector was used for the high-performance liquid chromatography. A C 18 (250 mm ? 4.6 mm ? 5 µ??) Regis analytical column was used. The mobile phase consisted of acetonitrile and isopropanol in a ratio of 85: 15; the flow rate was 1.0 mL/min and the analysis was conducted for 12 minutes at 40°C. Cholesterol was identified by comparing the retention time of the samples with the standard (SIGMA C8667-1G) and quantified through the corresponding peak areas by internal standardisation.

Sensory evaluation

To evaluate the sensory characteristics of the mortadellas, acceptance tests were performed to evaluate the differences perceived by consumers in the various formulations. Sixty consumers were recruited from students, faculty and staff at the Sao Paulo University (USP), Pirassununga, Brazil; consumers were recruited based on their affinity for the product. The samples were sliced into approximately 1.5 mm thick pieces just before the beginning of the tests and kept in a refrigerator (8°±1°C) during the entire sensory evaluation (about 3 hours). Consumers were accommodated in individual tasting booths where they received instructions about the use of the scale, the nature of the products and the type of evaluation to be carried out. Samples were served under white light in a randomised and monadic manner. The samples were served on small plastic plates coded with three-digit random numbers and with a plastic fork. For each sample, two superposed slices were served.

The consumers were asked to use a nine-point hedonic scale to evaluate the samples with regard to colour, odour (which should be evaluated by raising one of the slices of mortadella and smelling between the slices), flavour, texture and overall quality.

Statistical analyses

A completely random design with 3 treatments and 2 replicates was used. The data on physicochemical and technological parameters were analysed with an analysis of variance (ANOVA) to compare results among the treatments; means were compared using Tukey's test. Consumer acceptance data were analysed by ANOVA, using a mixed model, considering the random effect for panelist and the fixed effect for treatment. To evaluate the differences among the samples, a comparison of the means was carried out using Student's t test. Significance was defined at P ≤ 0.05, SAS® (©2000, SAS Inst. Inc.) software was used for the statistical analyses.

RESULTS AND DISCUSSION

Physical and chemical characteristics

There were no significant differences (P > 0.05) in the moisture, protein, fat and ash contents of the various treatments (Table 2); these findings show that the calculations used to determine the proximate composition of the formulations were adequate and that the emulsification and cooking processes did not affect the final composition of the products. Other researchers have also evaluated the use of vegetable oil instead of animal fat in sausages and have found no differences in the proximate composition of the products (BLOUKAS et al, 1997; VALENCIA et al, 2008; YILDIZ-TURP and SERDAROGLU, 2008), The fat, protein and moisture contents (Table 2) of the final products were in accordance with Brazilian legislation (BRAZIL, 2000) establishing the "Identity Standards and Quality of Mortadella"; these standards set maximum and minimum levels for some of these contents (maximum moisture of 65%, maximum fat of 30% and minimum protein of 12%), In addition to meeting current legal regulations, the mortadella formulations also simulated conditions normally found in the market. Some national commercial mortadella, made without apparent pork backfat pieces, contain 12,5% protein and 15% fat.

The hardness (compression strength) and tenderness (shear force) did not change significantly (P > 0,05) when animal fat was replaced with soybean oil (Table 2), Similarly, when 60% of the pork backfat was replaced with olive oil in a cooked meat batter with a total fat content of approximately 1 1%, FERNANDEZ-MARTIN et al (2009) found no difference in the hardness of the products (values were around 24-26 N), On the other hand, AMBROSIADIS (1996) found that the shear force values of frankfurter sausage made with 19,5% pork backfat were higher (1,7 kg) than those of frankfurters made with 19,5% soya oil (1,2 kg). The shear force values observed in this experiment (between 1,6 and 1 ,7 kg) were higher than those found by TRINDADE et al (2005) for mortadella prepared with mechanically separated chicken meat (between 0,3 and 0.7 kg). The higher shear force values found in this experiment may be due to the use of cellulosic casing, which is susceptible to moisture loss and may lead to dehydration in the cooking process.

No significant differences (P > 0.05) were observed in the process yields of the various treatments (Table 2). Because oils have a lower melting point than animal fat, greater losses due to dripping oil during the cooking process could adversely affect of the process yield; however, this effect was not confirmed. Emulsion stability and consequent losses due to cooking can be influenced by several factors, including the functionality of myofibrillar proteins, temperature, size of the fat droplets, pH, viscosity and the amount of salt used in the formulation (PARDI, 1994; COFRADES et al, 1998). All of these factors, combined with the addition of starch and soy protein in the various formulations, ensured stability and adequate yield despite the use of vegetable oil instead of animal fat (MATULIS et al, 1995). PAPPA et al. (2000) presented results similar to those of the present study; these researchers found no change in the process yield of low-fat frankfurters when pork backfat was replaced with olive oil (0-100%). HSU and YU (2002) evaluated an emulsified meatball (Kung Wan) prepared with various vegetable oils in place of pork fat and found no differences in the yield assessments during cooking between the control product (prepared with pork fat) and the product prepared with soybean oil.

All of the water activity values were approximately 0.95; there were no significant differences (P > 0.05) among the treatments (Table 2). This finding was expected because the formulations were calculated to present the same moisture contents; in addition, the same ingrethents were used in all of the treatments. Furthermore, the source of variation between treatments (vegetable oil or pork fat) does not influence water activity. The water activity values found in the present work are similar to those found by other researchers examining mortadella Bologna-type sausages; CÁCERES et al (2008) found that sausages with 1-6% flsh oil instead of pork backfat had a water activity value of 0.96-0.98, and NOWAK et al (2007) found that sausages with 3-12% inulin instead of pork backfat had a water activity value of 0.97.

The pH value of the mortadellas in this study was 6.2 and did not differ (P > 0.05) among the various treatments (Table 2), Our data agree with those of PAPPA et al. (2000), who also did not observe differences in the pH values (about 6.5) of low-fat frankfurters prepared with olive oil (0-100%) instead of pork backfat. The pH value may have an effect on proteins, which reach their maximum emulsifying capacity when the pH is close to neutral (MOHLER, 1982; MATULIS et al, 1995). The results of this study indicate that the meat proteins in the tested mortadellas show a good emulsifying capacity because the pH values were reasonably close to neutral.

Fatty acid profile and cholesterol content

The "Oil" treatment contained 5 1 .32% polyunsaturated FA (PUFA) and 26.40% saturated FA (SFA), the "50/50" treatment contained 33.69% PUFA and 34.89% SFA and the "Pork" treatment contained 16.00% PUFA and 46.60% SFA. The PUFA/SFA ratios of the three treatments were 1.94, 0.97 and 0.34, respectively (Table 3). The World Health Organization (WHO, 2010) recommends a PUFA/SFA intake ratio of one or higher; the Oil treatment exceeds this recommendation and the 50/50 treatment almost achieves it. The linoleic and a-Linolenic acid contents were higher (P < 0.05) in mortadella made with 100% soybean oil, and mortadella with 50% soybean oil gives an intermediate value that does not differ significantly (P > 0.05) from that of mortadella made with 100% soybean oil or with 100% pork backfat. On the other hand, the pork formulation shows a higher (P < 0.05) content of oleic acid. MUGUERZA et al (2003) evaluated "Chorizo de Pamplona" and observed that, as pork backfat was increasingly replaced with soybean oil (O25%), SFA, and particularly palmitic acid (23.7 for 18,8 g/100 g) and myristic acid (1.4 for 1.0 g/100 g), decreased while PUFA increased (15.2 for 23.9 g/ 100 g).

As shown in Table 3, the 50/50 treatment contained approximately 56% of the ?3 content found in the Oil treatment; this finding shows that the amount of ?3 was proportional to the amount of soybean oil added. Vegetable oils are the main source of ?6 fatty acids. The amount of ?6 in the three formulations declined considerably with the amount of soybean oil (i.e., Oil treatment > 50/50 treatment > Pork treatment). The co6 content was reduced by approximately 30.7% in mortadellas made with 100% pork backfat when compared to the mortadellas made with 100% soybean oil. In the 50/50 treatment, the ?6 content was reduced by exactly 49.85% of this 30,7% reduction, showing that the ?6 reduction results exclusively from the reduction in the soybean oil content. According to MOREIRA and MANCINI-FILHO (2004), the proportions of 0)6 and ?3 fatty acids should be balanced. Long-chain polyunsaturated fatty acids (EPA and DHA) are formed from the elongation and desaturation of linoleic and a-linolenic acids. When they are insufficient in diet, the body has to synthesise them from counterparts with a higher number of carbon atoms. Excessive linoleic acid will compete with the a-linolenic acid for desaturases, possibly leading to a low production of eicosapentaenoic acid. The World Health Organization (WHO, 2010) recommends that ?6 fatty acids make up between 5-8% of the total daily fat intake for healthy individuals and that 0)3 fatty acids make up between 1-2% of the total daily fat intake. It could therefore be inferred that a G)6 to ?3 ratio of about 4: 1 is necessary to maintain a balanced diet. In this study, the Oil treatment showed this proportion with a value of 1 1.25 (Table 3); this value is higher than the recommended value but is lower than the value shown by the Pork treatment (17. 19).

The Oil treatment showed a higher (P < 0.05) CLA1 content than the Pork treatment (Table 2). When we measured the total trans conjugated linoleic acid content (CLA1 + CLA2), we found that the Oil and 50/50 treatments showed high amounts of total CLA (0.76 and 0.62%, respectively) when compared with the Pork treatment (0.27%). CLA is a mixture of positional and geometric isomers of linoleic acid found primarily in dairy and meat products. Several studies indicate that CLA is a powerful compound that affects several different kinds of cancers, metastases, atherosclerosis, diabetes, immunity, and body fat/protein composition. This type of fatty acid is unique because it is present in food from animal sources, and its anticancer efficacy is expressed at concentrations close to human consumption levels (KRAMER et al, 2004; PARIZA et al, 2001).

The average cholesterol content of the three treatments did not differ significantly (P > 0.05) and were approximately 33 mg/100 g and 40 mg/100 g of sample for the Oil and Pork treatments, respectively (Table 3). This minor difference in the cholesterol content of the two treatments is probably because the beef meat contributes most of the cholesterol to the mortadellas. This type of meat, with 3% fat, contains approximately 52 mg of cholesterol per 100 g of meat (ALMEIDA et al, 2006). The tested mortadellas contained 54-58% beef meat (which contained approximately 3.5% fat); it is therefore possible that approximately 30-35 mg of the cholesterol present in every 100 g of mortadella were from the beef. A small contribution from pork backfat to the cholesterol content of mortadellas could also be expected. The cholesterol level in pork backfat is around 53 mg per 100 g (BRAGAGNOLO and RODRIGUEZ-AMAYA, 2002), and the 50/50 and Pork treatments included only 7.5% and 15% pork backfat, respectively. MUGUERZA et al (2003) found that cholesterol levels in Chorizo de Pamplona made with soybean oil (15-25%) instead of pork backfat were higher (92.96-87.71 mg/ 100 g) than those found in the present study; this higher cholesterol level was probably due to the higher level of fat (30%) added to the Chorizo de Pamplona. In general, the cholesterol levels found in all of the mortadella formulations were relatively low; a 100 g mortadella would contribute little more than 10% of the American Heart Association's (2009) recommended maximum daily intake of 300 mg of cholesterol.

Sensory evaluation

When sensoiy characteristics were evaluated (i.e., colour, odour, flavour, texture and overall acceptability), mortadellas made with 100% pork backfat scored significantly better (P < 0.05) on a number of variables than those made with 100% soybean oil (Table 4), Mortadellas made with 100% pork backfat and 50/50 pork fat and soybean oil had similar (P > 0.05) colour and texture attributes, although the pork formulation was more acceptable (P < 0.05) than the 50/50 formulation in the other attributes. However, while the Oil and 50/50 formulations had a similar odour and flavour, the 50/50 mortadella was significantly more acceptable (P < 0.05) than the Oil mortadella in colour, texture and overall acceptability. AMBROSIADIS et al (1996) observed a similar decrease in the sensory acceptability of emulsified cooked meat products when pork fat was replaced with vegetable oil (soybean, sunflower, cotton-seed and corn); however, their products maintained good quality for consumption. BROCE et al. (2007) evaluated the acceptability of the odour and taste of low fat chicken frankfurters that had a 10% fat content and were made with pork fat (control) or vegetable oil (canola, sunflower, olive or a mixture). These researchers found that the hedonic scores for the control sausage were highest and those for the sausage made with sunflower oil were the lowest; however, neither product showed scores that were significantly different from those attributed by the untrained panel to the rest of the vegetable oil sausages. CÁCERES et al (2008) added pre-emulsified fish oil (1-6%) to mortadella as a source of PUFA n-3 and evaluated the sensoiy acceptability of the products using a hedonic scale. Even with the addition of 6% fish oil, no changes were observed in colour, texture and overall acceptability and all of the batches were rated as generally acceptable.

All of the treatments in our study were acceptable; the Oil treatment received an average score of about 6 (liked moderately) while the Pork treatment received an average score of about 7. Moreover, absolute differences among the scores obtained for the three products, for all parameters, were small (less than 0.9 on a ninepoint hedonic scale). For example, the difference in the overall acceptability scores between the Pork and 50/50 treatments was smaller than 0.5. When developing this kind of product, the meat industry should consider the need to balance a loss in the sensory profile with a gain in the nutritional profile.

CONCLUSIONS

The use of vegetable oil instead of animal fat produced a healthier product with an improved fatty acid profile without affecting the physicochemical and technological characteristics of mortadella sausage. However, products with vegetable oil had less acceptable sensory characteristics than those made with the traditional animal fat. Replacing 50% of the pork fat with soybean oil is more acceptable, representing a good balance between nutritional gains and sensoiy biases.

ACKNOWLEDGMENTS

The authors would like to thank the State of Säo Paulo Research Support Foundation, Fundaçâo de Amparo à Pesquisa do Estado de Säo Paulo (FAPESP), for supporting the project: Replacement of pork backfat by soybean oil in mortadella: effects on chemical, physical and sensoiy characteristics (FAPESP No. 05/55199-0).

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Paper received April 13, 2010 Accepted June 29, 2010