Over the past few years, dairy researchers have been listening as medical and regulatory voices have raised concerns regarding the dietary intake of sodium for individuals with hypertension. Committed to helping the situation, researchers have been working to reduce the overall sodium content of cheese, but this effort has had its fair share of challenges. Salt modifies texture, helps control the moisture content, regulates acid development, provides flavor and contributes to the excellent safety record of fermented products like cheese.
So, modifying the salt content can be a difficult task. In last year’s sodium update column (January 2014), we discussed a few of the new cheeses and products that have come out of this research effort. This year, we will discuss the solutions and tests that researchers have been developing to deal with the effects of sodium reduction. Many methods show promise in producing a good quality reduced-sodium cheese, but there are always pros and cons to consider.
High moisture, soft texture
Higher-moisture cheese is one of the biggest defects associated with sodium reduction, as the lack of salt contributes to a softer texture. Cheesemakers can address this issue by making adjustments to the process, such as reducing the curd size or increasing the cook temperature. Research also suggests that incorporating calcium chloride during the dry salting phase increases the crosslinking of the proteins, creating a firmer cheese.
Even when the moisture content of a reduced-sodium cheese is adjusted back to the same moisture content of a cheese with typical sodium content, the texture of the reduced-sodium cheese generally remains softer. The sodium content (ionic strength) impacts interactions between milk proteins; reduced-sodium levels result in weaker interactions and thus softer cheese texture. High-moisture cheese also exhibits quicker protein breakdown during ripening (resulting in further softening), but recent research demonstrates that applying high-pressure processing (HPP) shortly after cheese manufacture slows the ripening process, allowing the cheese to stay firm.
Low pH (excessive acidity) is another common defect associated with sodium reduction in cheese. During cheese making, the starter cultures are responsible for the acid development. The addition of salt during the make process allows the cheesemaker to stop any further acid production, giving the cheesemaker a bit more control over pH. If sodium is reduced, however, then the starter cultures will continue to produce acid and the cheese will become more and more acidic. Research has shown that fortification of cheese milk with additional milk proteins can help with this issue by providing more “buffering” or greater resistance to a further drop in pH. This fortification can be especially helpful at the end of the manufacturing phase.
Flavor and consumer acceptance
Consumers expect a salty flavor in most cheeses and recent research has shown that consumer acceptance drops when there is a significant reduction in the sodium content. This may be partially due to another common defect in reduced-sodium cheese, bitterness. Salt provides a desirable flavor in cheese and it can also help to mask bitterness. The bitterness in a low-sodium cheese is often related to the production of a particular class of peptides that can be derived from an atypical breakdown of milk proteins. New types of rennet (e.g., camel chymosin) and selected starter culture or adjunct strains have been identified that reduce bitterness. Application of HPP to reduced-sodium cheese has also been demonstrated to reduce bitterness.
In addition to the solutions listed above, many companies use some (<30%) sodium replacers such as potassium chloride. Other sodium-reduction strategies used in the food industry include the use of:
- large salt crystals/flakes
- sea salt (which also contains potassium and magnesium salts)
- savory additives, and
- various flavor enhancers.
Until recently, however, there was no reliable, routine method to measure the sodium content in cheese made with salt replacers like potassium chloride. Thanks to funding from Dairy Management Inc., researchers at the Wisconsin Center for Dairy Research recently validated a new method for analyzing sodium in cheese, using x-ray fluorescence, a technique that is common in the mining industry. This method is quick and easy to use with both natural and processed cheeses (provided calibration is done with the specific emulsifying salts used in the processed cheese). The Journal of Dairy Science has accepted a paper describing this research, which will be published later this year.
So while reduced- and low-sodium cheese continues to pose a challenge to the dairy industry, research and innovation has taken several steps forward in meeting some of those problems.