Balancing low salt with substitutes, enhancers and alternatives
The main salt substitutes and enhancers used in processed pork products are potassium chloride, lactate, sodium nitrate and hydrocolloids. This section present the characteristics of the most common substitutes and enhancers used.
The main characteristics of the substances and enhancers used are described below.
Potassium chloride is often the material of choice in sodium-reduced meat products. It can produce a salty taste in small quantities. The disadvantage, however, is that its bitter taste can be noticeable in the finished meat product when larger quantities are used.
Sodium and potassium are present in their chloride salts in different proportions (KCl contains 52% potassium and NaCl contains 39% sodium). In addition, the atomic weight of potassium is greater than that of sodium. This results in a lower chloride ion concentration per unit weight of each salt, which has an effect on the chloride ion-dependent functionality of the meat proteins for water binding and fat emulsification. So, if sodium chloride has to be replaced by potassium, more potassium chloride has to be used in order to dissolve protein to the same extent (Feiner, 2006; Tarte, 2009).
In addition, it is also important to point out that potassium chloride behaves differently compared with sodium chloride. Na+ ions are structure-making (kosmotropic), while K+ ions are structure-breaking (chaostropic). Associated with this, water retention is greater with Na+ complexes with muscle structural proteins compared with potassium.
Lactate is added as the L-(+) lactic acid salt. It is different from lactic acid which is produced via controlled fermentation of sugar, which is L-(-).
L-(+) lactate inhibits the growth of a wide variety of micro-organisms and it is used for extending overall shelf-life. It extends the shelf-life of meat products by forming lactic acid once it has been introduced into the products. Un-dissociated lactic acid molecules penetrate into the cells of micro-organisms where they dissociate into H+ and lactate- ions. The H+ lowers the pH value of the cell cytoplasm. When the cell senses this change, it tries to rid itself of the H+ ions and raise its own intracellular pH value back to the original level. This process requires energy, leaving less for reproduction of the cell and therefore the speed of reproduction is reduced. Thus, lactate is not bactericidal, it is bacteriostatic. Currently, lactate is introduced into meat products as either sodium or potassium lactate (Feiner, 2006), and when the aim is to reduce sodium, potassium lactate should be the chosen option.
Sodium nitrite (NaNO2) is generally the material of choice to obtain a stable pink colour in cured meats. Nitrosomyoglobin (formed by the reaction of nitrite and myoglobin) is the heat-stable red colour. Nitrate (NO3) can be used with nitrite but it does not contribute directly to the formation of the red curing colour. It is the salt of nitric acid (HNO3) and it is reduced to nitrite, which then forms the curing colour.
Nitrite is also used in meat products because it provides the curing flavour, acts as an antioxidant, and has bacteriostatic effects. Briefly:
- The curing flavour originates from reactions between nitrite oxide (NO) with substances naturally present in meat (such as aldehydes, alcohols and some sulphur components).
- The antioxidant effect is based on the fact that nitrite oxidises to nitrate as well as forming complexes with the iron core of myoglobin and haemoglobin, reducing (i) the number of free iron ions and thus delaying the development of rancidity and (ii) the formation of metmyoglobin which is a pro-oxidant.
- Nitrite acts as a preservative against bacteria such as Salmonella spp. and Staphylococcus spp. but, more importantly, against Clostridium botulinum. Nitrite inhibits bacterial spores by inhibiting the germinated spore.
Nitrite has a major disadvantage, however. It has been implicated indirectly as a carcinogen. The presence of nitrite in cured meat products (specifically bacon) can cause the formation of N-nitrosamines, which at high intakes can cause cancer. However, nitrosamines are only obtained if the nitrite is present at the same time as secondary amines, which are very seldom found in meat products.
In low-sodium products, potassium nitrite is sometimes used.
Hydrocolloids, also commonly referred to as gums, originate from various sources and most of these are not digested in the human digestive system. Some examples are: carrageenan, alginate, agar, guar gum, locust bean gum (LBG), cellulose, starch and pectin.
Carrageenan is one of the hydrocolloids most frequently used in meat products. It originates from red seaweed. It can bind water and forms a gel once heated to around 70 °C and the gel is not heat-stable (heat reversible). There are three types of carrageenan: kappa (κ), lambda (λ) and iota (ι). The effects of each type of carrageenan in meat products differ in gel strength, viscosity and elasticity. The most used in meat products is the κ-carrageenan. The gel strength of κ-carrageenan is greatly dependent upon its concentration and the type of associated cation, resulting in stronger gels with K+ > Ca2+ > Na+. The role of cations in carrigeenan gelation is thought to be the building of helix dimers, thereby causing them to aggregate; potassium ions have excellent double-helix stability properties. Two types of κ-carrageenan are used in the meat processing industry: refined (E 407) and semi-refined (E 407a). Refined carrageenan contains around 1-3% insoluble matter (fibre, cellulose or hemicelluloses), while semi-refined contains up to 15% insoluble matter. Gels made from refined carrageenan are smoother, more elastic and clearer. However they are more expensive (Feiner, 2006; Lai et al., 2000).
List the advantages and disadvantages of each of the substitutes and enhancers described:
1 potassium chloride
3 sodium nitrate/nitrite