for New, Edible Adhesives
By Jan Suszkiw
December 19, 2003
Sugar isn't just for sweetening
anymore. Now, it's also the main ingredient in new, edible adhesives developed
by Agricultural Research Service
ARS chemist Sevim Erhan and colleagues at the agency's
National Center for Agricultural
Utilization Research in Peoria, Ill., developed the sugar-based, edible
adhesive concept at the request of a beverage packing company.
According to Erhan, who leads the center's
Food and Industrial Oils
Research Unit, the company needed a flavorless, food-grade adhesive that it
could use for an assembly line operation that inserts drinking straws into
beverage cans, cartons and bottles. Specifically, the company needed a strong,
fast-curing adhesive that could bond the straws to a special holder that's
lowered into the containers before they're filled and sealed. At that point,
the adhesive was supposed to dissolve in an even, controlled manner. Otherwise,
the straws would remain fixed to the holders instead of rising freely out of
the containers when consumers opened them.
Of the possible ingredients for the edible adhesive, Erhan and colleagues
Selim M. Erhan, formerly with ARS, and the late Kenneth Eskins chose sugar
because of its availability, familiarity to consumers, and widespread use in
beverages. Sugar alone isn't a strong adhesive. So, the researchers mixed it
with water and various organic acids. They then boiled the mixture until the
sugar and acids bonded, or cross-linked, forming a dark-yellow adhesive.
All told, they experimented with 10 different sugars, including sucrose,
lactose and maltose, and 12 organic acids, including citric acid, malic acid
and tartaric acid. Tests show the resulting adhesives bond to wood, metal,
cloth, leather, glass, plastic, paper and other materials. Exposed to liquids,
the adhesives dissolve and lose their grip in 20 to 60 minutes, depending on
the sugar/acid combination used to make them.
ARS, on behalf of the U.S. Department of
Agriculture, has patented the sugar-based edible adhesives (# 6,613,378
B1). Besides holding the straws, the adhesives have potential applications in
binding food items, food and utensil packaging, and drug capsule layers.
ARS is the USDA's chief scientific research agency.