(436b) Lactose Intolerance: a Simple Study of Kinetic Parameters Governing Lactose Conversion in Dairy Products

Lactose intolerance is a condition suffered by an estimated 50 million Americans. Certain ethnic and racial populations are more widely affected than others. As many as 75 percent of all African-American, Jewish, Native American and Mexican-American adults, and 90 percent of Asian-American adults are lactose intolerant (www. gastro.org ). Lactose, or milk sugar, is a naturally occurring dissacharide found in dairy products and is normally converted to simpler sugars in the human digestion process. The lactase enzyme (β-Galactosidase) hydrolytically cleaves the lactose molecule to form the monosaccharides, galactose, and glucose. This enzyme is secreted by cells along the lining of the small intestine during normal digestion. In some people, this enzyme is absent or is present in reduced concentrations. Interestingly, most other mammals completely stop producing lactase at weaning, and are thereafter intolerant of milk. If, during the human digestion process, lactose is not converted to these simpler sugars, people may suffer symptoms of bloating, nausea, cramps, and diarrhea. Hence the term, lactose intolerance. Fortunately, it is generally not life-threatening and can be controlled through proper diet. Also, there are various commercial lactase products available on the market such as Lactaid? and Dairy-Ease?. Lactase-deficient people can take these supplements orally with their meal to aid in digestion of dairy products. In the interest of appealing to high school outreach programs and funding-challenged college undergraduate departments, an inexpensive means was sought to monitor the kinetic reaction of conversion of lactose to glucose in milk. The obvious choice to monitor the reaction would be to adopt a standard glucose analyzer (Beckman, YSI et al.) commonly found in research and hospital laboratories. However, this complete set-up would cost over $10,000. Other methods considered were based upon refractive index, freeze point depression, use of a lactose probe, chromatography, and a colorimetric procedure. Finally, an inexpensive blood glucose monitoring meter (cost: $60), commonly used by diabetics to measure glucose levels in blood, was selected as a candidate for monitoring lactose conversion in milk. The commercial lactase enzyme, Lactaid?, was added to skim milk and lactose conversion to glucose was studied as a function of time with the blood glucose monitoring meter. Conditions of temperature, enzyme concentration, and pH were investigated. Michaelis-Menten parameters for these enzymatic reactions were also evaluated. These results will be presented at the 2007 AIChE Meeting.