source of salts and sugar in foods

Author: Monica 

Nitrates and nitrites

Nitrates helps in preventing oxidation (Doyle, 2007). Nitrate (NO₃), in the form of either sodium nitrate or potassium nitrate, is used as a source for nitrite (NO₂). Nitrate in meat products is converted into nitrite by the action of bacteria. The nitrite further breaks down in the meat into nitric oxide (NO), which then binds to the iron atom in the center of myoglobin's heme group, preventing oxidation (Sebranek, 1991). Nitrite acts as oxygen scavenger or anti-oxidative substance (Pegg, 2000). The interaction of nitrite in the meat acts as a chelating agent. Trace metals, as well as any liberated non-heme iron from denatured heme pigments are tied up and their effects inactivated (Sebranek, 1991).  Nitrate act as decreasing the Oxidation reduction potential (E_h) of cured meat, therefore at low pH 5.5 and below, the meat is not prone to oxidation and in addition, the initial lag phase of bacteria is prolonged (Lawrie, 1998). Oxidation reduction potential is a measure of the tendency of a chemical to be reduced through acquiring electrons. It is measured in E_h (1 E_h = 1 mV).

According to the Sales of Food Act, the legal limit for nitrites in products is capped at 250ppm. This is the legal and sufficient inhibitory amount of nitrites. Furthermore, nitrites help to prevent the spoilage due to the growth of Clostridium botulium. In the study of the effect of nitrite on the pyruvate metabolism of anaerobes, it was found out that the addition of nitrites caused the rate of hydrogen and carbon dioxide to reduce (Hill, 1991). The amount of the Adenosine Triphosphate (ATP) in cell had reduced quickly. This means that the cell has lost much energy, since ATP is the energy source of cell. Thus it was concluded that the presence of nitrites inhibits the pyruvate metabolism of anaerobes (Hill, 1991).

The outgrowth and germination of bacterial spores happens chronologically in five stages; germination (becoming non-refractile, stainable, heat sensitive), swelling of germinated spore, forming new vegetative cells, elongation and cell division. The spore of Clostridium botulisum after germination are inhibited when insufficient concentrations of nitrites were used, while sufficient concentration at 250ppm of nitrites inhibited the germination process itself (Sebranek, 1991).  This means although the germinated spores are inhibited with insufficient amount of nitrites, it is not able to prevent the dormant germinated spore’s activation when conditions are suitable. Therefore it is crucial that sufficient nitrites are used. Input concentrations of more than100 mg/kg (ppm) are used for protections against normal flora. At a concentration of 200 mg/kg at the pH of 6.0 is enough to inhibit the strains of Achromobacter, Aerobacter, Escherichia, Clostridium botulisum, Flavobacterium, Micrococcus, and Pseudomonas spp (Sebranek, 1991).

In addition to that, nitrites serves as an antioxidant giving the meat the stable colour and prevent the microbiological growth by retarding it. Apart from giving a pleasant flavor, it also help to prevent the development of oxidative rancidity in the beef. Nitrite also prevents lipid oxidation of cured meats by four mechanisms (Nation webmaster, 2005). The first mechanism is the formation of a stable complex between heem pigments and nitrites, thus preventing release of iron from porphyrin molecule. The second mechanism is the stabilization of unsaturated lipids within tissue membranes against oxidation. The third mechanism is the interaction of nitrite as a metal chelator so that it ties up trace metals in meat as well as any liberated non-heme iron from denatured heme pigments. And lastly, the fourth mechanism is the formation of nitroso and nitrosyl compounds in meat which possess antioxidative properties by acting as radical scavengers (Nation webmaster, 2005).

Salt (NaCl)

Salt is a multifunctional ingredient in cured meat. Sodium ions are responsible of contributing the flavor from salt. An important function of sodium in the perception of flavor is the increased intensity of other flavors that result in the presence of sodium (Ruusunen, 2005). Salt is also a flavor enhancer for the other flavor components in food.

Salt lowers the water activity of the food system by its osmotic property (Doyle, 2007). This also helps to make the conditions less suitable for micro-organisms to survive by inhibiting bacterial growth on the beef ham by dehydration and osmotic pressure (Hui, 2006). The salt penetrates through the beef ham and draw out moisture from it. Salt dehydrates the membranes of bacterial cells, thus inhibiting the growth of most pathogens in food (Ruusunen, 2005). Concluded from the study of Siegel (1981), a salt concentration of at least 13% is able to achieve inhibition of pathogenic microorganisms. However, a higher concentration, maximum 5g in one serving of the meat product, is needed to prevent loss of salt during process such as water drip. Five grams of salt is also the maximum recommended salt intake for adults (Health promotion board, 2010). Together with nitrates, both ingredients help inhibit C. botulinum spores from developing into toxins even at those higher smoking temperature (up to 82°C).  

Sucrose

Widely known as table sugar, is used to lower the water activity (a_w value) of the food system due to its hygroscopicity. Having the ability to retain water, it reduces water available in the food system and thus reduces the opportunities for the survival of micro-organisms. It gives the similar effect as the common salt (Forsythe, 1994). When sugar is rubbed onto the beef, it diffuses into the ham. Water present in the beef is extracted out through osmotic action, lowering the water activity (Doyle, 2007). Depending on the amount of water activity in the food, sugar is added accordingly to lower the water activity into the desired water activity.