Phosphates' Function in Poultry Products
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[Salt/Sodium Reduction] Vol. 17 No. 8 August 2007 ww Phosphates’ Function in Poultry Products By Andrew G. Ebert, Ph.D., Contributing Editor Food-grade phosphates perform a number of functions in processed poultry products. These properties include raising pH, increasing ionic strength and reacting with protein, which improves the water-holding capacity of the functional myofibrillar protein in poultry, thereby decreasing cook-cool loss, and creating improved and uniform yields. Phosphates protect against oxidation of lipids by binding metal ions that accelerate oxidation. They protect and preserve the natural flavor and color of poultry, and they solubilize protein, which is required in producing formed and restructured products, such as delicatessen rolls and chicken nuggets. Additive effects Studies with poultry products began over 40 years ago. Early applications involved static holding in solutions containing sodium tripolyphosphate (STPP), an alkaline phosphate, and sodium hexametaphosphate (SHMP). The most-notable food-technological effects were a 6.2% increase in moisture content and a rise in pH from 6.1 to 6.6, due to the addition of phosphate. With levels of phosphates used today, a more-modest rise (0.1 to 0.3 pH units, depending upon the phosphate or blend) would be anticipated. More recent studies have shown that the use of phosphates increases the temperature required for denaturation of protein and, thus, reduces cook-cool loss, leading to an end product with greater succulence. The addition of STPP and sodium chloride (NaCl) in poultry-processing formulations has been shown to have a number of advantages. First, STPP and NaCl increase ionic strength and synergistically extract myofibrillar protein. As protein becomes soluble, it develops a tackiness, which becomes a natural binder of moisture and meat pieces that is integral to the production of formed products, such as chicken and turkey rolls. A second reason to use STPP is to retard lipid oxidation, which often occurs when NaCl is used alone. STPP inhibits the oxidative effect of NaCl, and flavor is maintained. The dark meat of poultry inherently contains more iron, which can lead to the development of a warmed-over flavor. Phosphates in a poultry formulation will inhibit the development of such a flavor defect. In addition, the use of phosphates in combination with NaCl can result in a reduced level of the total sodium that needs to be listed on the nutrition label from about 1.0% to 0.5%. Food-grade phosphates are listed as GRAS by FDA. USDA meat and poultry regulations are described in Title 9 of the Code of Federal Regulations, Section 424, Part 21. A maximum level of 0.5% phosphate is permitted in processed meat and poultry products in the United States and 0.5% as disodium phosphate (DSP) in Canada. Selection criteria Pyrophosphates—tetrasodium pyrophosphate (TSPP) and sodium acid pyrophosphate (SAPP)—are the most rapidly acting phosphates in solubilizing myofibrillar protein, the water-binding protein of chicken and turkey. Alkaline pyrophosphates are not highly soluble in water, so they are usually blended with moresoluble, long- chain phosphates, such as STPP and SHMP, which are then hydrolyzed in the meat to the active pyrophosphate form. www.foodproductdesign.com Page 1 [Salt/Sodium Reduction] Vol. 17 No. 8 August 2007 For more broad-spectrum activity, SHMP, a strong sequestrant of metal ions, may be blended with STPP. SHMP will bind calcium and magnesium, the minerals that harden water, and may cause precipitation. Also, pyrophosphates are excellent iron chelators (binders) and, thus, are helpful in preventing the development of off-flavors and in protecting the natural color of poultry meat. The blends’ pH also impacts phosphate performance and functionality. The acid phosphate SAPP is rarely used alone, since it lowers the pH of the meat closer to its isoelectric point, which would lead to protein dehydration and discoloration. The most-common base phosphate for a blend is STPP, which increases pH. Orthophosphates, such as mono-, di- and tri-sodium phosphate, are not typically used in poultry products, since they have little or no action on protein. Similarly, calcium phosphates do not act at the protein level and are insoluble in water. They are only permitted in mechanically deboned poultry, where they preserve color during dehydration and in comminuted poultry products that contain functional phosphates to preserve color. To formulate poultry products with reduced sodium, sodium potassium tripolyphosphate (SKTP), potassium tripolyphosphate (KTPP) and/or tetrapotassium pyrophosphate (TKPP) may be used. Formulations containing the potassium salts must be tested at the benchtop prior to scaling up due to the stringent flavor note contributed by the potassium ion. Like sodium phosphates, potassium phosphates also help protect against damage during processing and handling, referred to by poultry scientists as “stressed meat syndromes,” and help overcome pH reduction and moisture loss sometimes seen in poultry following transport and handling. Phosphates, especially potassium phosphates, are hygroscopic by nature and should be stored under cool, dry conditions. When preparing solutions with phosphates, they should be dissolved first, followed by the addition of NaCl and other ingredients. Phosphate solutions should not be heated to promote dissolution, since heating causes polyphosphate to revert or break down to its orthophosphate form. This typically reduces pH and functionality. Phosphates should not come in contact with copper pipes if there are recirculation systems in use, as the copper will combine with an alkaline phosphate and cause a green discoloration of poultry meat. Poultry product formats Preparation of products such as wings involves vacuum tumbling. Alone, tumbling is useful when it is desirable to coat the pieces, such as Buffalo wings, with a viscous, flavored marinade. According to USDA regulations, only clear solutions may be injected. The injection technique is useful when the solution needs to penetrate throughout the meat, such as in the preparation of poultry-based delicatessen rolls. Tumbling after injection is indicated when the goal is to promote uniform penetration through the poultry meat and to avoid development of “pickle pockets.” The mechanical action of tumbling also accelerates the solubilization of the protein within the larger pieces of meat. Uncooked, frozen poultry products also benefit from the presence of phosphates that have a cryoprotective effect on the protein and lipids, and thus assist the protein in binding water and minimizing the moisture loss during thawing, and also protect against the development of rancid flavors. In the production of comminuted poultry, such as chicken nuggets and turkey franks, dry phosphate, sodium chloride and ice are added to the ground meat and physically mixed for dispersion and protein solubilization. The hydrated protein forms a matrix that entraps the fat. The presence of phosphate stabilizes the emulsion during the cooking process and results in decreased cook-cool loss. www.foodproductdesign.com Page 2 [Salt/Sodium Reduction] Vol. 17 No. 8 August 2007 Phosphates play an important role in designing convenient poultry products. Finding the optimum ingredient or combination on the bench can yield a range of beneficial effects. Andrew G. Ebert, Ph.D., is president of the International Food Additives Council (www.ifacmem.org), an Atlanta-based trade association representing the interests of manufacturers of high-purity substances used as direct food additives. He can be contacted at [email protected]. www.foodproductdesign.com Page 3 .