Mechanically separated meats (MSM) allow the recovery of valuable protein during carcass fabrication and are used throughout the world due to their low cost. However, MSM are susceptible to lipid oxidation due to high heme and free iron content, and they typically have a soft texture due to high connective tissue and low myofibrillar protein content.
MSM are generally shipped under frozen conditions and are used in processing of various products. Little research has been done to determine the effect of addition of MSM – especially that of pork MSM – on physicochemical characteristics of meat products (Baker and Kline, 1984; Raphaelides et al., 1998).
It is not unusual to have MSM stored for many months after production; but how does the quality change with length of frozen storage and how does that affect functionality?
The objective of the related study was to investigate functional properties of emulsion type meat product with various levels of frozen mechanically separated pork (MSP) (both five and eight months post production).
The MSP (22.5 percent fat, 14.3 protein) was obtained commercially, subdivided and randomly assigned to two frozen storage (-20°C) periods. After each frozen storage interval, the MSP meats were thawed at 1°C for 48 hours and coarsely ground. The control sausage formulation consisted of 56 percent to 68 percent fresh boneless pork shoulder (regular pork), 26 percent to 28 percent water, 3 percent salt, 0.3 percent sodium tripolyphosphate with ~10.5 percent fat and 12.5 percent protein content.
MSP was substituted for the fresh pork respectively (1:1). Four treatments (3.7 kg/treatment) of emulsion type sausage were produced with four addition levels of frozen MSP (0 (control), 5 (MSP-5), 10 (MSP-10), and 15 (MSP-15) percent of the formulation). The meats were chopped and emulsified with ingredients using a silent cutter and emulsion mill, respectively. Batters were stuffed in casings and then cooked in a water bath to a final internal temperature of 71°C.
Meat batters were assessed for water holding capacity (cook loss, expressible moisture and drip loss), protein solubility, viscosity and lipid oxidation (TBARS). The functional properties of cooked sausage such as texture profile analysis, torsional shear values (shear stress and strain at failure) and TBARS were evaluated. Lipid oxidation of regular pork and MSP also were determined. The data were analyzed using the General Linear Model (GLM) procedure of the SAS statistical package. Differences in means between treatments were determined using Duncan’s multiple range tests (P<0.05).
The MSP had higher (P<0.05) lipid oxidation compared to regular pork. One reason may be the greater aeration during deboning (Hrynets et al., 2011). The lipid oxidation of MSP increased to 4.0 mg from 1.8 mg MDA/kg meat from five to eight months of frozen storage.
In general, with an increase in the additional level of frozen MSP to 15 percent from 5 percent, there were significant (P<0.05) increases (P<0.05) in cook loss (from 0.6 to 1.0 %), expressible moisture (from 18 to 23%) and lipid oxidation (from 1.0 to 1.7 mg MDA /kg meat) and decreases (P<0.05) in viscosity (from 1.0×105 to 1.1×105), hardness (from 109 to 63 N) and torsional shear value (from 37 to 19 KPa).
However, 5 percent and 10 percent of frozen MSP addition did not influence WHC (cook loss, expressible moisture and drip loss), protein solubility (total soluble and sarcoplasmic protein) and hardness compared to the control sausage. The expressible moisture and cook loss are the parameters commonly used to determine the effects of treatments on the quality characteristics of meat products. The present study found quality properties such as cook loss and expressible moisture of meat products were not greatly influenced by addition level (up to 15 percent) of frozen MSP.
Extended frozen storage of MSP (of up to eight months) generally led to deterioration in WHC, lipid oxidation and instrumental hardness, while viscosity and torsional shear values were not affected by freezing storage periods of MSP. We were interested in the effect of even longer frozen storage, and thus similar sausage were prepared with addition of MSP following 14 months of frozen storage.
The addition of frozen MS pork for 14 months resulted in large changes in gelation properties (higher shear stress at failure and lower shear strain), which manifested as an increase in firmness and loss of elasticity compared to samples prepared with MSM stored for five and eight months. Researchers also found that torsional shear value (shear stress at failure) was greatly influenced (P<0.05) by an additional level of frozen MSP as frozen storage periods increased.
Shear stress at failure dropped 48 percent, 50 percent and 72 percent between MSP-5 and MSP-15 in each frozen storage period (five, eight and 14 months, respectively). In other words, a suitable addition level of MSP that has no adverse effect may depend on prior frozen storage duration of the MSP in meat products.
The results suggested that substitution of 5 percent frozen MSP may contribute similar functional properties compared to the control formulation and may deliver a more economical product of comparable quality.
In general, sausages with up to 10 percent additional levels of frozen MSP had similar WHC and torsional shear as meat products with 100 percent regular pork. Functionality of frozen MSP continues to decline during frozen storage, with noticeable differences in sausage properties due to a three-month difference in frozen storage time (eight months compared tov five).
Good management of MSM meats is essential to the production of high-quality processed meats.
This project was supported by the Saskatchewan Agriculture Development Fund and the Saskatchewan Pulse Growers.
References
Baker, R.C., Kline, D.S. (1984) Acceptability of frankfurters made from mechanically deboned poultry meat as affected by carcass part, condition of meat and days of storage. Poultry Science 63 (2), 274–278.
Hrynets, Y., Omana, D. A., Xu, Y., Betti, M. (2011) Impact of citric and calcium ions on acid solubilization of mechanically separated turkey meat: effect of lipid and pigment content. Poultry Science 90 (2), 458-466.
Raphaelides, S. N., Grigoropoulou, S., Petridis, D. (1998) Quality attributes of pariza salami as influenced by the addition of mechanically deboned chicken meat. Food Quality and Preference 9 (4), 237–242.
– Juhui Choe and Phyllis J. Shand, University of Saskatchewan, Saskatoon, Canada