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How industry makes ice cream

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The summer weather is here, and if you've been out in the sun, you're probably craving some ice cream to cool off. In the American Chemical Society's latest Reactions video, American University Assistant Professor Matt Hartings, Ph.D., breaks down the chemistry of this favorite frozen treat, including what makes ice cream creamy or crunchy, and why it is so sweet.

When you're not being told by the brain to stop eating, you overeat. That's what can happen when you eat enough ice cream that has a taste you enjoy the most, for example chocolate mint chip, or crunchy dark chocolate crumbled cookies in ice cream, which a lot of people like. You may wish to check out the YouTube video, "Ice Cream Science." Reactions looks at the chemistry involved in making the treat creamy and sweet. Most people don't like ice cream full of sharp, watery ice lumps. And some people taste fat as creamy and delicious, whereas others taste whipped frozen fat as simply fat and somewhat nauseating, especially if its not sweet enough or too sweet or too tart. Others like the taste of cinnamon, cloves, and a touch of ginger and walnuts in ice cream.

Dark chocolate lovers show higher tolerance for bitterness in chocolate ice cream

To make the inherent bitterness of cocoa in chocolate ice cream more palatable, manufacturers add high levels of fat and sugar. Yet, bitterness is an integral part of the complex flavor of chocolate. In a 2013 study, "Explaining tolerance for bitterness in chocolate ice cream using solid chocolate preferences," published in the August 2013 issue of the Journal of Dairy Science®, (Elsevier Health Sciences) investigators report that consumers who prefer dark chocolate in solid form tolerate twice the amount of bitter ingredients in chocolate ice cream than those who prefer milk chocolate. Elimination of some added sugar and fats in chocolate ice cream may be acceptable, and perhaps preferable, to some consumers.

"Our primary goal was to determine whether rejection thresholds for added bitterness in chocolate ice cream could be predicted by individual preferences for solid milk or dark chocolate," says senior author John E. Hayes, according to a July 24, 2013 news release, "Dark chocolate lovers show higher tolerance for bitterness in chocolate ice cream." Hakyes is an assistant professor of food science and Director of the Sensory Evaluation Center, College of Agricultural Sciences, The Pennsylvania State University, University Park, PA. "Estimating rejection thresholds could be an effective, rapid tool to determine acceptable formulations or quality limits when considering attributes that become objectionable at high intensities."

The research team produced a control sample of plain chocolate ice cream and samples with varying levels of sucrose octaacetate, a food-safe bitter ingredient used to alter the chocolate ice cream's bitterness without disturbing other the sensory qualities of the samples, like texture

These samples were offered in pairs to 96 members of the Penn State community who were non-smokers between the ages of 18 and 45. Forty-six participants preferred milk chocolate. All participants were asked to indicate which of the two blind samples they preferred. They each tasted one spoonful of ten different samples, rinsing with water between pairs.

As expected, the group that preferred solid dark chocolate showed a significantly higher rejection threshold – about twice as high -- for sucrose octaacetate in the chocolate ice cream than the group that preferred milk chocolate. "These results suggest that this approach could be used to make chocolate ice cream with less added sugar to be marketed for dark chocolate lovers, though this needs to be formally tested," says Dr. Hayes, according to the news release.

"Rejection thresholds can also be applied to other dairy foods in quality control or product optimization applications as a means to determine specific concentration limits associated with preferences." Further, the research team has demonstrated that the use of the rejection threshold methodology can be used effectively with solid, and not just liquid, foods.

Ice cream may target the brain before your hips, a 2009 UT Southwestern study suggests

Blame your brain for sabotaging your efforts to get back on track after splurging on an extra scoop of ice cream or that second burger during any given Friday night's football game. Findings from a new UT Southwestern Medical Center study suggest that fat from certain foods we eat makes its way to the brain. Once there, the fat molecules cause the brain to send messages to the body's cells, warning them to ignore the appetite-suppressing signals from leptin and insulin, hormones involved in weight regulation.

The researchers also found that one particular type of fat – palmitic acid – is particularly effective at instigating this mechanism. "Normally, our body is primed to say when we've had enough, but that doesn't always happen when we're eating something good," said Dr. Deborah Clegg, according to a September 14, 2009 news release, "Ice cream may target the brain before your hips, UT Southwestern study suggests." Clegg is an assistant professor of internal medicine at UT Southwestern and senior author of the rodent study, "Palmitic acid mediates hypothalamic insulin resistance by altering PKC-θ subcellular localization in rodents," appearing in the September 2009 issue of The Journal of Clinical Investigation.

When your brain gets 'hit' with food high in fat, you become resistant to insulin and leptin

"What we've shown in this study is that someone's entire brain chemistry can change in a very short period of time. Our findings suggest that when you eat something high in fat, your brain gets 'hit' with the fatty acids, and you become resistant to insulin and leptin," Dr. Clegg said, according to the news release. "Since you're not being told by the brain to stop eating, you overeat."

Dr. Clegg said that in the animals, the effect lasts about three days, potentially explaining why many people who splurge on Friday or Saturday say they're hungrier than normal on Monday. Though scientists have known that eating a high-fat diet can cause insulin resistance, little has been known about the mechanism that triggers this resistance or whether specific types of fat are more likely to cause increased insulin resistance. Dr. Clegg said she suspected the brain might play a role because it incorporates some of the fat we eat – whether it is from healthy oils or the not-so-healthy saturated fat found in butter and beef – into its structure.

Based on this suspicion, her team attempted to isolate the effects of fat on the animals' brains. Researchers did this by exposing the animals to fat in different ways: by injecting various types of fat directly into the brain, infusing fat through the carotid artery or feeding the animals through a stomach tube three times a day. The animals received the same amount of calories and fat; only the type of fat differed. The types included palmitic acid, monounsaturated fatty acid and oleic acid.

Palmitic acid is a common saturated fatty acid occurring in foods such as butter, cheese, milk and beef. Oleic acid, on the other hand, is one of the most common unsaturated fatty acids. Olive and grapeseed oils are rich in oleic acid.

Palmitic acid (very high in foods rich in saturated fat) reduced the ability of leptin and insulin to activate signaling inside cells

"We found that the palmitic acid specifically reduced the ability of leptin and insulin to activate their intracellular signaling cascades," Dr. Clegg said, according to the news release. "The oleic fat did not do this. The action was very specific to palmitic acid, which is very high in foods that are rich in saturated-fat."

Dr. Clegg said that even though the findings are in animals, they reinforce the common dietary recommendation that individuals limit their saturated fat intake. "It causes you to eat more," she said, according to the news release.

The other key finding, she said, is that this mechanism is triggered in the brain – long before there might be signs of obesity anywhere else in the body. The next step, Dr. Clegg said, according to the news release, is to determine how long it takes to reverse completely the effects of short-term exposure to high-fat food.

Other UT Southwestern researchers involved in the study included Dr. Carol Elias, assistant professor of internal medicine, and Drs. Boman Irani and William Holland, postdoctoral research fellows in internal medicine. Researchers from the University of Cincinnati, Tennessee Valley Healthcare System, Vanderbilt University School of Medicine and the University of Paris also contributed to the study. The National Institute of Diabetes and Digestive and Kidney Diseases supported the study.

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