Millions of pounds of nutrient-rich ice cream go to waste each year, according to the International Dairy Foods Association, discarded after production. Nearly 5% of the raw materials used in ice cream production end up as waste - representing millions of dollars in lost product per year. This waste primarily results from batches thrown out for quality issues and equipment cleaning. Adding to this, regulations aimed at preventing cross-contamination with allergens have enlarged the dairy product's waste footprint, greatly increasing the amount of discarded ice cream over the past two decades.
An answer to this waste may be to recycle the ice cream waste, according to researchers in Penn State's College of Agricultural Sciences. They found that it is possible to recover a large amount of fat at a potentially economical cost. Recovered fat could potentially be used to replace a pork fat called choice white grease that is mainly used in animal feed, or transformed into compounds for use in pharmaceuticals, cosmetics and other products, the team said. They published their findings in Cleaner Engineering and Technology.
They found that ice cream waste, which typically has a fat content three to five times that of cows' milk, doesn't necessarily need complicated treatment to recover its fat. Simple separation, particularly centrifugation - a mechanical process that uses rapid spinning to separate mixtures of different sizes, shapes and densities - with alkaline treatment as a possible aid, will get the job done.
"Here in the Department of Food Science at Penn State we have a close relationship with the food industry, so it was through our industry partners that we first heard about the magnitude of the ice cream waste problem," said study senior author Yi Zhang, Frederik Sr. and Faith E. Rasmussen Career Development Professor in Food Science. "After offering the Ice Cream Short Course for over 100 years, we have ties to nearly every major ice cream company in the world, so we wanted to see whether we could help solve the problem."
In the study, the team worked with Perry's Ice Cream in Akron, New York, which shipped about 90 pounds of frozen ice cream waste per batch - with fat content ranging from 1.8% to 10.3% - from four production batches that had been mixed at the ice cream manufacturing facility.
The first approach researchers tried to collect the milk fat was a process called proteolysis - using enzymes such as pepsin, trypsin and bromelain to break down proteins that help stabilize the fat emulsion. The second approach was pH shifting, in which they made the waste strongly acidic (pH 2 or 4) or alkaline (pH 11) to destabilize the emulsion. After treatment, they centrifuged the material to separate the fat.
The team measured fat recovery - how much of the original fat they successfully recovered - and fat purity - how much of the recovered material was actually fat rather than proteins, water and other compounds. The result was somewhat surprising, Zhang noted.
