Chemistry

Every day in the news, it is reported that childhood obesity is a growing problem. Many doctors have linked children’s weight gain to the drinking of juice instead of milk and water. Most parent feel good about giving their children 100% juice with no sugar added, thinking it is nutritious. The Center for Disease Control and Prevention notes that children need very few calories per day and the sweet drinks, like apple juice, are a source of added sugar in their diet. In response to dietary concerns, the Food and Drug Administration requires food labels listing the amount of sugar for apple juice. Are the labels on apple juice correct? This topic is important because it affects all children who enjoy drinking apple juice.
In the last 30 years, children have increased the amount of juice they drink because of convenience and advertisements. Sweetened drinks are preferred over unsweetened drinks by children and almost all children by one year of age are drinking fruit juice. Children in one study drank on average 5.5 fluid ounces of juice per day. The juice that 35% of kids prefer is apple juice. This study also showed that children who drank more juice had higher intakes of fruit sugars, fructose and glucose. The result of the study did show a relationship between drinking apple juice and a child’s weight through the BMI, body mass index. The body mass index is the relationship between a person’s height and their weight.

Since children do like sweet drinks like fruit juice, it is important that parents read the food labels to decide what is good for their children to drink. The Nutrition Facts food label gives information about the nutrients in food. Most nutrients are measured in grams, shown as g. Other information is shown as percentages. The percentages are based on a 2000 calorie diet. The following is the information that is on all food labels.
Serving Size – a specified amount of food, for apple juice this is 8 fluid ounces
Servings per Container – the number of servings in the bottle or can
Calories or Calories from Fat – The number of calories in a single serving, for 8 ounces of apple juice this is 120 calories
Percent Daily Value – This is the percentage of the recommended daily allowance for several nutrients. Apple juice labels show Total Fat – 0g, 0%; Sodium – 25mg, 1%; Potassium - 280mg, 8%; Total Carbs - 29g, 10% of that Sugars are 26g; Protein – 0g; Vitamin C 120% and Iron 2%
It should be noted that the information on the labels are based on an adult’s needs not a child’s.
These food labels are required by the Food and Drug Administration (FDA). The FDA inspects all food suppliers to assure the labels are correct. As a result, scientists must have ways to measure all the information on the labels. In order to measure the amount of sugar in apple juice, scientists use high performance liquid chromatography. This technique shows them the total amount of sugar in the juice and which sugars, fructose, glucose, or sucrose, are in the juice.
Chromatography was invented by Russian botanist Mikhail Tswett. He was looking for a way to separate the pigments in plants. He used a glass column packed with calcium carbonate, the different pigments looked like different bands on the column. Chromatography is made up of a stationary phase and a mobile phase. Mixtures are carried through the stationary phase by the flow of the mobile phase and separations are based on the differences of the how well the different components are held by the stationary phase before being taken by the mobile phase. In high performance liquid chromatography (HPLC), the mixture is forced through a column of the stationary phase by introducing a liquid mobile phase at high pressure. For sugar analysis, the HPLC column is a special carbohydrate column (stationary phase) and the mobile phase is varying amounts of water and another solvent, acetonitrile. The sugars are then detected by either a refractive index detector (RI) or an evaporative light scattering detector. The detector communicates with the computer software when the light it emits is bent by the compound as it comes off the stationary phase. The detector then provides qualitative data, which sugar it detects, and quantitative data, how much of that sugar is detected.

Scientists at the juice companies use HPLC to determine the content of sugar in their products. This amount is then placed on the food label as required by laws enforced by the Food and Drug Administration. From these food labels, parents can decide if they will give the juice to their children to drink. They will also need to decide if the amount of sugar in the drinks is okay for their kids. They depend on the label to be correct.

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