Guest Columns

Perspective:
Dairy Ingredients

Lactose and permeate — part of our everyday lives

Stephanie Clark

Stephanie Clark is manager of academic engagement at the American Dairy Products Institute, Elmhurst, Illinois, and emeritus professor of food science at Iowa State University. She contributes this column exclusively for Cheese Market News®.

Do you ever wonder what happens to lactose or permeate when not used in food?

Take a look around you — one of them may be part of something you use every day.

Once considered “waste,” or at best, “byproducts” of the dairy industry, lactose and lactose-rich whey permeate are now valuable co-products that have a multitude of applications in the dairy, food and non-food industries. Just a few of the applications demonstrating the value of lactose and permeate in non-food uses are summarized in this mini-review.

Since the 1930s, when lactose was used as a filler or as placebo tablets in drug efficacy research, lactose has been used as a tableting excipient (bulking agent). The fact that it is sweet is only part of the reason — the functional properties (e.g., tensile strength, disintegration) of the three forms of lactose (i.e., α-anhydrous, β-anhydrous and α-monohydrate) have also made it a go-to compound (in approximately 70% of oral solid dosage formulations) for drug delivery for nearly 100 years.

In the cosmetics industry, hyaluronic acid (HA) has gained popularity recently, particularly with help from advertisements featuring models carefully pronouncing the compound to provide familiarity with the scientific term. Streptococcus thermophilus can produce HA, but an abundant carbon source is necessary for it to do so. Both whey permeate (82% w/w lactose) and whey protein hydrolysate (20% degree of hydrolysis) can serve as suitable feedstocks for S. thermophilus to produce HA.

Dairy ingredients may be an invisible component of a building near you. As early as the 1960s, these ingredients were being studied for production of rigid polyurethane foams. The hydroxyl groups of lactose cross-link with isocyanate groups, and water reacts with isocyanate groups to produce carbon dioxide (CO2).

With the help of an oxidizing agent (propylene oxide) and catalyst (potassium hydroxide), a polyether polyol can be formed. When combined with urea, flame-retardant (self-extinguishing) low-density polyurethane foams are produced. Some of the common adhesives used to produce laminated composites like fiberboard, chipboard and plywood are potentially hazardous and consume petroleum resources. Alternative environmentally friendly lactose-based adhesives exhibit excellent bonding properties and shear strength in dry, hot and boiling water. The tendency for concrete to crack limits its structural integrity and durability.

Fortunately, not all microcracks develop into unstable cracks, and in fact, may “self heal” through a combination of chemical, physical and mechanical processes, often involving formation of calcium carbonate (CaCO3). When microcracks allow water into concrete matrix, bacteria can become active, produce CaCO3 and seal the cracks. The fact that several bacteria can produce CaCO3 (e.g., in caves, soils) has been exploited. By mixing bacteria into cement and aggregate, along with other fillers (e.g., lactose, permeate), natural “microbial concrete” can fill microcracks and improve durability of concrete.

Multiple forms of energy can be produced from lactose, whey, permeate and even delactosed permeate (DLP). Bioethanol is among the most extensively explored value-added products that can be obtained from these dairy ingredients. Scientists analyzed the possibility of using permeates to produce electricity and heat from biomethane generated during anaerobic digestion. Some investigators have utilized microalgae or yeast for biodiesel production from lactose, permeate or DLP. A less common fuel source, hydrogen (H2), is a clean energy source because it does not contribute to greenhouse effects. Select anaerobic bacteria (e.g., Clostridium, Bacillus, Enterobacter) can consume organic material and produce H2 gas and other compounds (e.g., CO2, organic acids). Several authors have demonstrated the potential of biohydrogen production from lactose or whey.

Prompted by high crude oil prices, commercialization of polyhydroxyalkanoate (PHA) biopolyesters (bioplastics) began in the 1970s. PHAs are naturally produced by some bacteria, are non-toxic to humans and other life forms, are biodegradable and have similar properties to polypropylene. Several investigators have demonstrated that whey, whey permeate or hydrolyzed whey permeate can be good options for production of PHAs.

In the early 1990s, it was demonstrated that whey permeate can be converted into calcium magnesium acetate (CMA) to replace salt as non-corrosive, more environmentally benign road de-icers. More recent research revealed the potential for fermentation of whey permeate with acid-tolerant L. plantarum and/or L. buchneri to produce acetate and propylene glycol for road and aircraft de-icing applications.

Not yet convinced that lactose or permeate could be anywhere? Consider the clothing you wear. To reduce the amount of harmful textile dyes entering the environment, chromophores can be transferred onto lactose to create glycol-azadyes for efficient dying of wool, polyester, cotton, nylon and acetate without the need for dispersing agents, surfactants or mordants. Furthermore, indigo dyeing of denim involves an oxidation-reduction reaction. In its original form, the oxidized pigment is insoluble. Addition of a reducing agent in alkaline conditions cleaves disulfide linkages to form a partially soluble “leuco” sulfur form of the dye, which enables adsorption and diffusion into cotton. Air-drying enables the leuco dye to oxidize back to the original form, resulting in blue denim jeans. Sodium dithionite (Na2S2O4), the most common reducing agent, is environmentally unfavorable because sulfite and sulfate cause problems when discharged into wastewater.

Investigators have demonstrated that lactose can be used as a reducing agent, at elevated temperatures under alkaline conditions, to substantially reduce the amount of Na2S2O4 needed (by approximately 50%).

Although maligned by some, because of the discomfort it can cause upon consumption, lactose is arguably the dairy component with the most potential for value-addition. With diverse applications in pharmaceutical, construction, renewable fuels and plastics, clothing and more, lactose and permeate are of value to all of us in one form or another. The relatively low cost of these ingredients, and the abundant research demonstrating their applicability, should serve as a springboard for future research and valorization opportunities.

CMN

The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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