- Phosphate addition to meat products improves their texture and yield.
Phosphates are commonly found in meat and poultry products because they improve yield, texture and permit moisture retention. They are slowly replacing sodium chloride in meat products although they still contribute some sodium. It’s also worth noting that phosphates, especially polyphosphates are used routinely in toothpastes (White, 2002).
For many years now, the meat industry and public health bodies globally have looked to reduce sodium chloride intake because of the link to high blood pressure (hypertension). Currently phosphates as additives in food supplements can be used at quantum satis (i.e. as much as technologically needed). Unfortunately from a product development point of view, a low salt meat product is susceptible to spoilage and even compromises food safety. The other aspect of low salt is poor texture and lower cooking yields of the meat product. Such weakness in product attributes soon leads to poor consumer confidence and acceptance which have been ameliorated using phosphates as a replacement.
Common practice now is to combine both salt and phosphates because both act synergistically. Salt also enhances the effectiveness of phosphates (Hamm, 1970; Poulanne and Terrell, 1983; Trout and Schmidt, 1984).
The Behaviour Of Phosphates In Meat And Cooked Meat Products
It is thought that the mode of action of phosphates is many fold.
The main functional property of phosphate is to change the pH of the meat system. According to Jeff Sindelar, associate professor in the department of animal science at the University of Wisconsin-Madison (Fuhrman, 2015) he states in the National Provisioner article:-
“The main functionality is to change the meat system pH, so that we are moving the pH of the meat further away from the isometric point,” he explains. “The isometric point of meat is around 5.2 to 5.3. By adding phosphates, we are adding additional charges to the meat system. Because of that, you are creating an imbalance between positive and negative charges, so you are changing basically the ionic strength in the meat system. You are causing the proteins to push away or swell, and because of that, you create more space for the protein charges that can grab onto water and bind water. This is also essentially the same mechanism of cooked sausages, which is where phosphates can help with protein extraction, and they do so by kind of the same type of mechanism.”
It is most likely that the meat pH is slightly raised which is a hurdle for pathogens as is ionic strength (IS). There is also improved resistance created by binding of phosphate to various proteins coupled to dissociation of actomyosin into myosin and actin. Protein systems which are to be cooked or processed further benefit from a slightly higher pH and ionic strength because water or moisture binding improves as a result (Lawrie & Ledward, 2006).
Generally, the ionic strength and pH can operate independently of each other in a protein food. If you increase the ionic strength using neutral food salts, the pH becomes more acidic. There is also an alteration in buffering capacity as well as pH because of the addition salts of weak acids such as the corresponding phosphoric acids.
The buffering capacity of a salt is determined by its concentration, its pKa, the pH of the medium in which it operates and the presence of other acids and bases in the milieu. The pKa of sodium tripolyphosphate is 9.25 (Martell & Smith, 1976).
When it comes to it, judging how much phosphate to add is based on trial and error. One study assessing the effect of sodium tripolyphosphate (STPP) in chicken patties found that there was a direct effect on ionic strength (Papa et al., 1992). The conclusion was that this phosphate can alter the texture of a meat product such as chicken when the pH of the product is close to the pKa of the tripolyphosphate. The role of pH in this regard is not so important.
A possible issue with phosphates, especially polyphosphate as an additive is the possibility that it might bind and sequester minerals such as calcium. This might influence bone reabsorption and affect calcium uptake but there is still a lack of evidence to support this view. Likewise, many of the alternatives to polyphosphate might also have health implications.
Currently, phosphates (E 338–341, E 343, E 450–452) are authorised food additives in the EU with maximum permitted levels (MPLs) ranging from 500 to 20,000 mg/kg in 104 authorised uses and at quantum satis (QS) in four products.
Incidentally, the polyphosphates in European legislation do not refer to diphosphates or triphosphates. The polyphosphates have the E number E452. (The E numbers for diphosphates, E450 and triphosphates are E451).
Phosphates are not permitted in fresh meat but could be added to meat preparations, minced meat and meat products (Regulation EC No 853/2004, 2004).
The maximum permitted level of phosphates in meat and meat products according to European legislation is 5 g/kg as phosphorus peroxide (P2O5) individually or in combination to the finished product (Directive No 95/2/EC, Rev. 2006).
According to FAO/WHO food standards, the maximum permitted level of phosphates (singly or in combination) is: (i) 2200 mg/kg as phosphorus (approximately 5041 mg/kg expressed in P2O5) in the finished product as frozen processed poultry meat and game products, in whole pieces or cuts and in processed comminuted meat, poultry and game products (Codex Stan. 192-1995, Rev. 2010); (ii) 3000 mg/kg as P2O5 in the finished product as luncheon meat (Codex Stan 089-1981, Rev. 1991), in cooked cured ham (Codex Stan 096-1981, Rev. 1991), in cooked cured pork shoulder (Codex Stan 097-1981, Rev. 1991) and in cooked cured chopped meat (Codex Stan 098- 1981, Rev. 1991).
Safety Issues On Phosphates
In July 2019, EFSA (European Food Safety Authority) issued new advice regarding phosphates when they found that the estimated total intake of these ingredients exceeded the safe level set by the agency.
EFSA recommended the introduction of maximum permitted levels to reduce the content of phosphates in foods as additives, particularly processed meats and supplements.
The chair of EFSA stated:
“The panel has reassessed the safety of phosphates and derived, for the first time, a group acceptable daily intake (ADI) of 40 milligrams per kilogram of body weight [mg/kg bw] per day.”
“Because phosphates are also nutrients and essential to our diets, in our approach we defined an ADI which considers the likely phosphorus intake from various sources, including natural sources and food additives.”
The ADI corresponds to an intake of 2.8 grams of phosphorus per day for an average adult weighing 70 kg (about 154 lb).
It is thought based on estimated calculations that phosphate from food additives contributes between 6% and 30% of the total average intake of phosphorous.
The chair of EFSA’s expert Panel on Food Additives and Flavorings (FAF) stated:
“We estimated that dietary exposure to phosphates may exceed the new ADI for infants, toddlers, and children with average consumption of phosphates in their diet. This is also the case for adolescents whose diet is high in phosphates.”
“The data we had did not give rise to safety concerns in infants below 16 weeks of age consuming formula and food for medical purposes containing phosphates.”
If you are looking for advice on how much phosphate should be added to meat burgers and patties, ask us at FoodWrite Ltd. A number of manufacturers are also looking to remove polyphosphates from meat products and there are alternatives which are said to be based on proteins and fibre that could provide a suitable alternative.
Fuhrmann, E. (2015) Phosphates: Highly Functional, Hard To Replace. The National Provisioner/Independent Processor. January 21, 2015 (Article)
Hamm, R. (1971). Interactions between phosphates and meat proteins. In Symposium: Phosphates in Food Processing, Ed. deMan, J.M. and Melnychyn, P., University of Guelph, Ontario, Canada. Ch. 5 p. 65 AVI Publishing Co., Wesport, CT. USA.
Lawrie, R. A., & Ledward, D. A. (2006). Lawrie Meat Science.
Martell, A. E., & Smith, R. M. (1974). Critical stability constants (Vol. 1, p. 135). New York: Plenum Press.
Papa, C., Lyon, C., & Wilson, R. (1992). Moisture retention and textural properties of ground chicken meat as affected by sodium tripolyphosphate, ionic strength and pH. Journal of Food Science, 57(6), pp. 1291-1293
Puolanne, E. J., & Terrell, R. N. (1983). Effects of Rigor‐State, Levels of Salt and Sodium Tripolyphosphate on Physical, Chemical and Sensory Properties of Frankfurter‐Type Sausages. Journal of Food Science, 48(4), pp. 1036-1038 (Article)
Trout, G. R., & Schmidt, G. R. (1984). Effect of phosphate type and concentration, salt level and method of preparation on binding in restructured beef rolls. Journal of Food Science, 49(3), pp. 687-694
White, D.J. (2002) A New and Improved “Dual Action” Whitening Dentifrice Technology – Sodium Hexametaphosphate. J. Clin. Dent., 13(1) pp. 1-5