How to measure nutritional value of food?

Aside from being legally required on a food label in most countries worldwide, the nutritional value also serves to help customers make choices around the products they want to buy.

Some people may be in search of products high in protein, or can’t handle high amounts of sugar. The nutritional value label on a product tells a consumer exactly what is in a product. A consumer can literally determine what the nutritional value of a food is for their body. Does it provide energy? Or does it provide certain components that are crucial for their health?

The ingredient list simply tells you which ingredients a food contains. The nutritional value digs a little deeper. It then analyzes what these ingredients are made up of and groups these components.

First of, a nutritional value states how much energy a product contains. This is the amount of energy that a human body can get out of these ingredients. We all need energy on a daily basis to function properly.

Secondly, the nutritional value states which types of molecules are present in the food and how many. These molecules are split into functional groups. The most common molecules are:

These are macromolecules. Almost every food and drink contains at least one of these (except for pure water for instance). We humans need them to live. These ingredients are also the main energy source of foods.

Carbohydrates and fats can be split up into smaller groups of molecules. For instance, carbohydrates might be split into sugars, and fats can be split into saturated and unsaturated fats.

There’s more to good food than just proteins, carbohydrates and fats. We also need certain vitamins and minerals. These can also be found on labels.

Before attempting to determine the nutritional value of a product, keep in mind that foods are highly variable. The less processed a product is, the more this is the case.

As such, it is almost impossible to give very precise correct nutritional values for food. There will almost always be some variations, simply because you can’t analyze every apple from a batch and give it a different value. Often nutritional values are averages for a specific product.

That does not mean nutritional values are useless. They still provide clear differences between products, just be aware that it is not as exact a science as you might think it is.

Determining the nutritional value starts by determining how much of each of the components your food contains. So how much proteins, carbohydrates, fats, vitamins, etc. does your food contain?

There are three main ways in which you can determine these:

There exist a wide range of analytical methods that can be performed on foods to determine their nutritional value. Methods exist to determine the types and amounts of sugar, fats, etc. Laboratories will state which methods are required to get a full nutritional profile of a product.

All of the analyses required are chemical analysis techniques. These techniques tend to only use very small amounts of sample to make a determination. Knowing how variable products can be, it is important to make sure that this small sample size is actually representative of the product you’re testing.

Once you’ve prepped the sample, let’s have a look at the possible analytical methods involved. Keep in mind that there may be more options than the ones mentioned below.

Foods tend to contain a lot of different proteins. It is virtually impossible to analyze how much there is of each protein, nor does it provide a lot of added value. That’s why most labels only require the overall protein content.

Proteins are some of the only molecules in food that contain nitrogen. As such, by analyzing how much nitrogen a product contains, you can calculate the overall protein content. There are two main analysis techniques used for this: the Kjeldahl method and the Dumas method.

Depending on where you live, you might also need to take into account the quality of the protein. Some proteins are more ‘complete’ than others. Some countries require you to correct the overall protein content with a separately determined factor (e.g. a PDCAAS score).

There exist a lot of different carbohydrates, from small to large. Unlike proteins, they don’t contain a unique atom. On the contrary, it is quite similar to fats. It’s why in a lot of cases, the carbohydrate content is etermined by taking the total mass of a product and subtracting all the other components (fats, protein, water, ash, etc.). What remains is assumed to be the carbohydrates.

If you do need to know exactly which types of sugars a product consists, it is possible to determine those using a technique called liquid chromatography.

Most of the fats in foods are the so-called triglycerides. An important property of fats is that they don’t dissolve in water. As such, they can be extracted from most products. This extraction method can be used to determine the overall content.

If you need to know exactly which tryglycerides are present in a food you will have to use a more advanced technique such as gas chromatography. This is however quite an expensive and complex technique.

Over time, a wide range of products have been analyzed for their nutritional content. When determining the nutritional value of your product, you might be able to use these existing values for your product.

A lot of countries have their own databases of generally acknowledged nutritional values for food products. The USDA, in the USA, has a very extensive, publicly accessible database. The Netherlands has one as well, as do many other countries.

Let’s start with the 2nd option: the literature route. In this case, no analysis of the actual final product is done. Instead, databases which contain a lot of data on nutritional values of all sorts of products are used.

If your product is made with your own recipe and has a unique composition, you will not be able to find literature values for it. However, you may find the nutritional value of the ingredients that you used. If so, you can use those to calculate the nutritional value of your product.

You will have to know how much of your recipe is made up by each ingredient. It’s easiest to state this in percentages. Then, you can use these percentages to calculate how much of each nutrient your product contains.

As an example:

These calculations can be quite simple and reliable if all you’re doing is mixing ingredients. However, if a lot of chemical reactions take place in your product, or if significant amounts of water evaporate, this no longer works well. Some molecules might have reacted and become something different for instance.

Once you know the composition of your product, you can easily determine the energy content of your food. The energy content of a food is determined by the amount components that your body can use to make energy. These are the three macronutrients, protein, carbohydrates, and fat, but also alcohol, polyols (strictly a type of carbohydrate) and fibers (also a carbohydrate type).

The energy content of a food is given in kcal (often referred to as Calories) and/or kJ (kilojoule). Converting from kcal to kJ is a simple set calculation

1 kcal = 4,18 kJ

Research has shown how much energy our body can make from these macronutrients. We know that:

Using the conversion factors above, you can calculate the energy content of your food by multiplying these values by the amount of each of the macronutrients present.

As an example, let’s look at imaginary product A. In the table below we’ve given how much fat, proteins, and carbohydrates this product contains per 100g of the product. By multiplying these values by the given conversion factors and adding up the result, you can the overall energy content.

So, if you want to determine the nutritional value of your product, start by deciding whether you will be able to find relevant data in existing literature. If so, you can use those to calculate the nutritional value of your food, sometimes requiring some additional calculations. If not, you will have to send your product to a laboratory for analysis.

Liliana Krotz, Elena Ciceri and Guido Giazzi, Protein Determination in Cereals and Seeds, August-1, 2008, link ; for more detail on protein determination

RIVM, NEVO online, link ; Dutch database with nutritional values for wide range of products

University of Massachusetts, 6. Analysis of Proteins, link ; for more detail on protein determination

There are two ways to determine the nutrition information of your food products. You can determine by laboratory analysis or by calculation. Laboratory Analysis involves you sending your finished product to a laboratory where they will physically test the product using approved methods.

The calorie and nutrient content of single ingredients and individual foods can usually be found in the USDA’s National Nutrient Database. In addition, most packaged foods list information in the Nutrition Facts panel. Follow the steps below to find nutrition information for a single food or ingredient: 1. Go to the USDA National Nutrient Database. 2. Search and select food item of interest. Sometimes there are multiple options (e.g. chicken breast with and without skin; roasted, fried, etc.) so choose the option that is the best match for the food you are using. 3. Input the amount of food and click “apply changes.”  Note that there are gram values for all provided unit measures, which is the same unit used on the Nutrition Facts label.

For example, if you want to know the calorie content of 2 cups of a food item, adjust the numerical value in the column titled “cup” to 2.

Other unit conversions may sometimes be necessary if the unit of interest is not an available option. For example, if you want to know the calorie content of 8 oz of a food item but only the value for 100 grams is available, then you will need to adjust the numerical value in the column titled ‘value per 100 grams’ to 2.27.

1 oz = 28.4 grams 8 oz = 227 grams (8 x 28.4 grams) 227 grams/100 grams = 2.27 (so you would need 2.27 times the 100 gram value)

Calories, nutrients and weights displayed for each food are for the edible portion of food (for example – without bones, etc.)

A lot of the foods we eat have more than one ingredient. For example, a chicken breast is rarely prepared plain and may include some type of fat used during cooking, a sauce added afterward, or other ingredients. Multi-ingredient recipes can be calculated by entering data for each individual ingredient into an MS Excel® spreadsheet that has been set up for this purpose. The spreadsheet gives you the option to list how many servings the recipe makes and will calculate the calories and nutrients per serving. Follow the steps below to calculate the nutrition information for a multi-ingredient food or recipe.

Typically a meal consists of several different foods, some of which may be recipes that contain multiple ingredients. An example would be a stir fry (recipe with multiple ingredients) with a side of rice (single ingredient). Calorie and nutrient values for meals can be calculated by entering the values for the individual ingredients and for the single serving portion of recipes into a downloadable MS Excel® spreadsheet that is set up for this purpose. Follow the steps below to calculate the nutrition information for a meal.

The USDA database does contain some ready calculated meals, however, we recommend you calculate the nutrient information for your dishes as described above, in order to obtain the most accurate composition for your own recipes.

The more precise you can be with the exact food, amount, and servings per recipe, the more accurate the calories and nutrient values will be. Also, be aware of often forgotten ingredients such as oil, butter, or broth used in cooking.

The methods described above assume that all of the fat used in cooking is consumed. For deep fried items, however, select the appropriate choice directly from the USDA database.

The following nutrition analysis resources are available for purchase and will do the work for you. This list is not exhaustive and not an endorsement of any products or companies.Nutritional Analysis SoftwareAxxya SystemsESHA – Genesis R&D SQLESHA – Food Processor SQLFoodWorksMenuCalc

Nutrition Analysis Companies (some may also perform laboratory analysis)Compu-Food Analysis, Inc.Energyent, Inc.Food Consulting CompanyHealthy Dining FinderKitchens with ConfidenceNutriData

National Laboratory Analysis Companies  (some may offer volume discounts. Call for pricing.)

California Michelson Laboratories, Inc. 6280 Chalet Drive Commerce, CA 90040

Michelson Laboratories of Northern California 1451 Moffat Blvd. Suite #1 Manteca, CA 95336 562-928-0553 888-941-5050www.michelsonlab.com

Colorado Industrial Laboratories Company, Inc. 4046 Youngfield Street Wheat Ridge, CO 80033 303-287-9691www.industriallabs.net

Warren Analytical Laboratory 650 “O” Street Greeley, CO 80631 970-475-0252 800-945-6669www.warrenlab.com

Connecticut Northeast Laboratories, Inc. 129 Mill Street, Suite 11 Berlin, CT 06037 800-654-1230www.nelabsct.com

Illinois Silliker, Inc. 900 Maple Road Homewood, IL 60430 708-957-7878www.silliker.com

Iowa Eurofins Scientific, Inc. 2200 Rittenhouse Street, Suite 150 Des Moines, IA 50321 515-265-1461http://www.eurofinsus.com

Louisiana Intertek Total Quality Assurance 160 James Drive East, Suite 200 Saint Rose, LA 70087 888-400-0084 or 281-971-5600www.intertek.com/risk-management/consumer-goods/total-quality-assurance/

Massachusetts Krueger Food Laboratories, Inc 21 Alpha Road, Suite D Chelmsford, MA 01824 978-256-1220www.kfl.com

Minnesota Medallion Labs 9000 Plymouth Avenue North Minneapolis, MN 55427 1-800-245-5615www.medlabs.com

Nebraska Midwest Laboratories 13611 B Street Omaha, NE 68144 402-334-7770www.midwestlabs.com

Food Processing Center, University of Nebraska-Lincoln 143 Filley Hall 402-472-2832http://fpc.unl.edu/

New York Certified Laboratories, Inc. 200 Express Street Plainview, NY 11803 800-CERT-LAB or 516-576-1400https://certified-laboratories.com/

North Carolina Craft Technologies, Inc. 4344 Frank Price Church Road Wilson, NC 29893 252-206-7071www.eurofinsus.com/food-testing/laboratories/eurofins-craft-technologies/

Oregon Element Portland - Parkrose 12003 N.E. Ainsworth Circle Suite #105 Portland, OR 97220 503-253-9136www.element.com/locations/the-americas/portland---parkrose

Pennsylvania Microbac 100 Marshall Drive Warrendale, PA 15086 724-772-0610www.microbac.com *27 locations in the East and Midwest

Our bodies get energy from the food we eat. When we digest food, our bodies use some energy right away and store the rest of the energy for later. Our bodies use energy for three main things. These include digestion, physical activity and other body functions.

Ideally, we take in as much energy as we need. If we take in more energy than we need, our bodies will store the extra energy as fat. If we take in less energy than we need, our bodies will get energy from stored fat. Neither too much or too little energy is a good thing.

A calorie is a measure of energy. The calorie number we see on food labels refers to a kilocalorie (kcal), which is also known as a large calorie or a food calorie. A kilocalorie is 1 000 calories. One kilocalorie is the amount of energy it takes to heat one kilogram of water one degree Celsius at sea level. For foods, the calorie count is a measure of how much energy that food stores in its chemical bonds.

Your age, biological sex, and physical activity levels all affect how many calories you need. For example, a sporty, active person needs more calories than someone who is less active, or sedentary.

Turning the energy from food into energy that the body can use is called metabolism. Metabolism is actually a series of chemical reactions. Each reaction breaks down food and releases energy.

A person’s basal metabolic rate is the rate at which their body uses energy while at rest. In other words, it’s how much energy your body uses when you are not doing anything. Your basal metabolic rate is responsible for up to 70% of the calories your body uses.

The nutrition label also gives information about the amount of three main nutrients in the product. These main nutrients are fats (lipids), proteins and carbohydrates.

Some calories you consume every day should come from each of the three nutrients.

Reading nutrition labels can help you determine how much of these key nutrients you are getting from your food.

To measure the fat content in a food, the food is ground up and then mixed with a chemical that dissolves only the fat. This method can be long and quite complicated.

To make the process quicker and easier, scientists are looking at a technique called nuclear magnetic resonance. In this technique, food is bombarded with a pulse of radio waves. This affects the atoms in the molecules that make up the food. Fats react differently to these pulses than other types of molecules. This makes this technique useful for determining the amount of fat in the food.

Since protein is high in nitrogen, by measuring the nitrogen in a food, you can get a good sense of how much protein is in that food. One way to measure the nitrogen in food is through the Kjeldahl method. In the Kjeldahl method, the food is heated in boiling sulphuric acid (H2SO4). The acid decomposes the organic molecules and produces ammonium sulphate (NH4)2SO4. Next the ammonium sulphate is distilled with a small amount of sodium hydroxide (NaOH). This converts the ammonium (NH4+) to ammonia (NH3) gas. The ammonia gas can then be separated and measured using acid-base titration.

Carbohydrates aren’t specifically measured in food. Instead, they’re calculated. Scientists measure the amount of protein, fat, and water in food. They add these numbers together. Then they subtract that sum from the total weight of the food. The difference is the amount of carbohydrates in the food.

By reading nutrition labels, you can ensure that your body is getting the right amount of fats, proteins, and carbohydrates you need to stay healthy.

Be careful, though. The measures of energy on labels tell you how much energy the food contains. It doesn’t measure how much energy you can actually get from it. That’s because some foods take a lot more energy to digest than others.