A common macronutrient used in
curing is
salt, which increases the osmolarity of the liquid to inhibit the growth of certain classes of microorganisms. This effect creates a difficult environment for those bacteria to survive in and allows the growth of salt-tolerant microbes. Salt also helps extend
shelf life. The juice from the lemon is acidic and contains
citric acid that helps lower the
pH, which additionally restricts microbes that can cause spoilage and disease. For preservation of lemons, the use of
antioxidants as a
food additive is used to prevent
lipid peroxidation and the fading of food color. Although lemons contain citric acid, most citric acid is produced by fermentation using microbes that can convert sugars into citric acid, which is the most important
organic acid produced in tonnage and is extensively used in food and pharmaceutical industries. It is produced mainly by submerged fermentation using
Aspergillus niger or
Candida spp. from different sources of carbohydrates, such as
molasses and starch-based media. The food and beverage industries use this acid extensively as a food additive globally. ==See also==