Nutritional composition table is an essential part of prepackaged food labeling, except for some prepackaged foods exempted from mandatory nutrition labeling, other prepackaged foods must be labeled with nutritional composition table.

GB 28050-2011 “National Standard for Food Safety General Principles for Nutrition Labeling of Prepackaged Foods”, “3.4 Nutrient content of food should be labeled with specific values, which can be obtained through calculation of raw materials or product testing”. The testing method is a more direct and accurate method. The theoretical calculation method is also a good method, not only can save time and testing costs, if calculated properly, the calculated value is very close to the actual nutrient content.

Theoretical calculation method is applicable:

• When the ingredients in the product formula have been clearly defined, the data is accurate and sufficient;
• The product already has nutrient content data, and after adjusting the formula, it can be calculated on the basis of the nutrient content of the original formula;
• The results of theoretical calculations and the test values of nutrients can be verified with each other.

This paper focuses on the calculation of the mandatory labeling of the nutrient content table, including: energy, the content values of core nutrients (protein, fat, carbohydrates, sodium) and their percentage of the nutrient reference value (NRV). It is hoped that it can provide a reference for food companies’ R&D and quality control personnel on the calculation method of nutrient content.

Nutrient content claims, comparative claims, as well as modification intervals and “0” thresholds refer to GB 28050-2011 “General Principles for Nutrition Labeling of Prepackaged Foods of National Food Safety Standards”, which will not be discussed in detail in this article.

Calculation of Protein, Fat, Carbonic Acid Compound and Sodium Content

1. Calculation of protein

Protein is a nitrogenous organic compound with amino acid as the basic unit, which is an important nutrient providing energy.

The protein content of a food product can be calculated either by the food ingredients themselves for which accurate data are already available, or by nutrient data from trusted food composition databases.

Protein content is usually calculated using the following formula:

Protein (g/100g) = Total Nitrogen (g/100g) x Protein Conversion Factor

The conversion factors for protein in different foods are shown in Table 1. For processed foods containing two or more protein sources, a conversion factor of 6.25 is used consistently.

Table 1. Protein conversion factors

Image source: GB 5009.5-2016 National Standard for Food Safety Determination of Protein in Foods

Calculation of nitrogen content in food additives:

For some foods, monosodium glutamate and disodium nucleotides presenting flavor are commonly used flavor enhancers, especially in the flavorings used in a high proportion, so the calculation of total nitrogen can not be ignored, the calculation method is as follows:

1. Nitrogen content of monosodium glutamate: 14/187=7.49%=7.49g/100g

In which the molecular weight of monosodium glutamate (containing 1 molecule of water of crystallization) is 187

2, flavor nucleotide disodium nitrogen content: 63/530 = 11.89% = 11.89g/100g

The average molecular weight of disodium nucleotides (containing 7.25 molecules of water of crystallization) is 530.

3、Other nitrogen-containing food additives with the same calculation method (1) and (2)

Protein content in food is:

Protein (g/100g) = ΣPercentage of raw materials×Corresponding nitrogen content (g/100g) ×Corresponding protein conversion factor + ΣPercentage of nitrogen-containing food additives×Corresponding nitrogen content (g/100g) ×6.25

Note: The result of protein calculation retains one digit after the decimal point, i.e., accurate to 0.1g.

2. Calculation of fat

Crude fat is a large class of food insoluble in water and soluble in organic solvents (ether or petroleum ether) compounds in general, in addition to triglycerides, but also includes phospholipids, sterols, pigments, etc., the detection method is through the determination of crude fat (crude fat) or total fat (total fat) and get the fat content. It can also be calculated by the following methods to get the theoretical value.

(A) High fat content of raw materials by 100% of the proportion of fat content

Commonly used fat raw materials, including: vegetable oils, animal fats, anhydrous cream, margarine, oil-soluble food flavor, oil-soluble pigments, phospholipids, etc., can be directly calculated as 100% of the crude fat content;

(B) other fat-containing raw materials, calculated according to the actual fat content

Commonly used fat-containing raw materials include: meat and its extracts, aquatic products and its extracts, grains and its roughly processed products, soybeans and its roughly processed products, egg yolks and yolk products, milk and dairy products, nuts and seeds, etc., which can be calculated according to the proportion of the raw materials in the food and the corresponding fat content of the raw material.

The fat content in the food is:

Fat (g/100g) = Σcontent of ingredient counted as fat in 100% proportion (g/100g) + Σpercentage of other fat-containing ingredients x fat content (g/100g)

Note: fat calculation results are retained to one decimal place, that is, accurate to 0.1g.

3. Calculation of carbohydrates

Carbohydrate is a general term for monosaccharides, disaccharides, oligosaccharides and polysaccharides, which are important nutrients for providing energy. Detection method is usually based on the total mass of food as 100, minus the measured mass of protein, fat, moisture, ash, called “total carbohydrates”. The calculation method is directly based on the sum of starch and sugar as “carbohydrates”.

(i) Starch and sugar are directly included in the carbohydrate content at 100%.

Commonly used raw materials are: starch, dextrin, dextrose, sugar, fructose, xylose, crystalline maltose, etc., can be directly according to 100% of the carbohydrate content;

(B) other raw materials containing carbohydrates, according to the actual carbohydrate content calculation

Commonly used carbohydrate-containing raw materials include: grains and their roughly processed products, potatoes and their processed products, soybeans and their roughly processed products, fruits and their processed products, vegetables and their processed products, spices and their roughly processed products and so on. Calculations can be made based on the proportion of the ingredient in the food and the corresponding carbohydrate content of the ingredient.

The carbohydrate content of the food is:

Carbohydrate (g/100g) = Σcontent of ingredient counted as 100% carbohydrate (g/100g) + Σpercentage of other ingredients containing contained carbohydrates x carbohydrate content (g/100g)

Note: Carbohydrate calculation results are retained to one decimal place, that is, accurate to 0.1g.

4. Calculation of Sodium

Sodium in food refers to the sum of sodium present in food in the form of various compounds. Salt is the main source of sodium in food. In addition, monosodium glutamate and disodium nucleotides, which are commonly used as flavor enhancers in salty foods, are also important sources of sodium and are calculated as follows.

(1) The sodium content in sodium chloride is.

23/58.5=39.3%=39.3g/100g=39300mg/100g

(2) The sodium content in monosodium glutamate is.

23/187=12.3%=12.3g/100g=12300mg/100g

(2) The sodium content of disodium nucleotides is: 46/530=8.68%.

46/530=8.68%=8.68 g/100g=8680mg/100g

(3) For other sodium-containing foods and food additives, the calculation method refers to (1)-(3)

The sodium content in food is:

Sodium (mg/100g) = ΣPercentage of raw materials × corresponding sodium content (mg/100g)

Note: The result of sodium calculation is reserved to single digit, i.e. accurate to 1mg.

5. Trans fatty acids

Trans fatty acids are the sum of unsaturated fatty acids containing 1 or more non-conjugated trans double bonds produced in the processing of fats and oils, excluding natural trans fatty acids. When hydrogenated and/or partially hydrogenated fats and oils are contained in food ingredients or used in the production process, the trans fat (acid) content should be labeled.

Products whose ingredients contain hydrogenated and/or partially hydrogenated oils as the main raw material, such as margarine, shortening, phylloxera and cocoa butter, should also be labeled with the content of trans fats (acids). However, if hydrogenated oils are not used in the above products, it is up to the enterprises to choose whether or not to label the content of trans fatty acids.

The naturally occurring trans fatty acids in food products are not required to be labeled, and enterprises can voluntarily choose whether or not to label them. If an enterprise makes a claim on TFA, it is required to label its content mandatorily and must comply with the claim requirements in the standard.

When the proportion of hydrogenated oils and/or partially hydrogenated oils in the ingredients is small, or the hydrogenation of vegetable oils is relatively complete, resulting in a very low content of trans fatty acids, the content of trans fatty acids in the final product is lower than the threshold value of “0”, and the trans fatty acids should be labeled as “0” in this case. In this case, the TFA should be labeled as “0”.

Calculation of energy

According to the calculated protein, fat, carbohydrate content, refer to the corresponding energy conversion factor, protein conversion factor of 17 kJ / g, fat conversion factor of 37 kJ / g, carbohydrate conversion factor of 17 kJ / g. Energy can be calculated.

Energy (kJ/100g) = Protein (g/100g) x 17 kJ/g + Fat (g/100g) x 37 kJ/g + Carbohydrate (g/100g) x 17 kJ/g

Note: Calculations of energy are retained to the nearest integer, i.e. to the nearest 1 kJ.

Calculation of Nutrient Reference Value (NRV)%

Nutrient Reference Values (NRV, NutritionReference Values) are reference values used to compare the level of nutrient content of food products. Comparing the nutrient content with NRV enables consumers to better understand the level of nutrient content.

The specified reference values for energy and 32 nutrients are shown in Table 2.

Table 2 Nutrient Reference Values (NRV)

Image source: GB 5009.5-2016 National Standard for Food Safety Determination of Protein in Foods

The nutrient reference value percentage (NRV%) of the food is:

NRV%= Nutrient content/corresponding nutrient reference value×100%

Note: The results of Nutrient Reference Value Percentage (NRV%) of food are reserved to single digit, i.e., accurate to 1%.

GB28050 stipulates that the allowable error of energy and core nutrient content is “protein, carbohydrate ≥ 80% of the labeled value; energy, fat, sodium ≤ 120% of the labeled value”. According to the calculated values of energy, core nutrients (protein, fat, carbohydrates, sodium) and their percentage of nutrient reference value (NRV), the values of energy and nutrients should be combined with the permissible error ranges of energy and nutrients, and the values of energy and nutrients should be revised. A nutrient content table is then produced. An example is shown in Table 3.

Table 3 Example of nutrient composition table

This article discusses in detail the calculation methods of protein, fat, carbohydrate, sodium and energy and nutrient reference value percentage (NRV%). Because food types and nutrient composition varies greatly, other not exhaustive discussion and elaboration of the content, should refer to GB 28050-2011 “Food Safety National Standard Nutrition Labeling of Prepackaged Foods” in the specific requirements of the nutrition labeling labeling.

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The Nutrient Reference Calculator can be used to calculate energy values, NRV% for energy and core nutrients, and sums of major nutrients (for checking if the sum of nutrients in 100g/ml exceeds 100). The trimming method of NRV% calculation in the table is set as rounding. Since the NRV% calculation of the Nutrition Facts Table can also be trimmed by using rounding 5 into 5, when the calculated NRV% in the table differs from the labeled value by 1, it needs to be calculated manually in order to ascertain whether the NRV% calculation is in accordance with it or not. (Provided by “kingwuguo”, download address: http://bbs.foodmate.net/thread-1278659-1-1.html)

Take prepackaged condiments as an example

Explaining the precautions to be taken when making nutrition labels[1]

Not all condiments need to be labeled with nutrition labels. GB 28050 clearly defines the scope of foods that need to be labeled with nutrition labels. Some condiments do not need to be labeled with nutrition labels, such as vinegar, spices belong to the food that is consumed in small quantities and contributes little to the body’s nutrient intake, and pure monosodium glutamate (MSG) belongs to the single-ingredient food. However, like sauce, soy sauce, curd, etc. are mandatory to label the nutritional composition table, and the production of nutrition labels for some condiments that need to be labeled with nutritional information is discussed next.

Firstly, we collected local representative condiments, such as prepackaged Sichuan kimchi, chicken essence seasoning, spicy sauce and soy sauce in 1 group each. The content of each nutrient was tested according to GB 5009, etc., and then the carbohydrate content and energy value were calculated with the characteristics of the products. The test results were compared with the manufacturers’ nutritional content list printed on the products’ packaging, and the reasons for the differences were analyzed.

The nutrition labels of the samples are generally consistent with those produced by the enterprises, but the carbohydrate content of kimchi, the protein content of chicken essence, the fat content of soy sauce have more obvious differences in the values, and the values of sodium content fluctuate greatly, as shown in Tables 4 to 7.

When the condiment (e.g. kimchi) is composed of two phases, solid and liquid, the influence of the sample on the final result should not be ignored whether the test sample is based on the homogenization of the mixture of the two phases or only for the drained product. It is advisable to indicate when labeling the Nutritional Composition Table whether the calculation is based on the drained product or not, so as to ensure the consistency of the test data.

When seasonings contain a lot of non-protein nitrogen, such as chicken seasoning, they contain a lot of monosodium glutamate. In this case, if the nitrogen content of the sample is determined by Kjeldahl method alone and multiplied by the protein conversion factor of 6.25 without screening, the result can only be on the large side.

The accurate method is to first test the total nitrogen content, then deduct the content of non-protein nitrogen, and then multiply the difference by the appropriate protein conversion factor in order to arrive at an accurate protein content. In reality, the protein content of chicken flavorings is very small.

If the seasoning contains a lot of coloring, it is very dark in color, but at the same time it contains almost no fat of its own. Whether the fat is determined by Soxhlet extraction or by acid hydrolysis, the result will be on the large side because the coloring will be soluble in extracts such as petroleum ether.

In this case, it is better to determine the fat content according to the ratio of raw materials and then combined with the production process. Because of the change of GB 28050 in the fat content requirements is not more than 80% of the labeled value, so even if the labeled fat content is “0”, as long as there is no special emphasis on fat-free, it can be interpreted as the fat content in the “0” limit value below the labeled value is The concern that the labeled value is “0” while the actual content exceeds “0” is purely superfluous.

For samples with high viscosity (soy sauce, paste), it is more convenient to express the content in terms of mass (e.g. per 100g), and the calculation results are accurate.

In summary, there are the following considerations for nutrition labeling of condiments:

• Test several times to obtain the average value. Retest nutrient content and produce nutrition labels once the process formulation has changed;
• Consider the interference of non-protein nitrogen on protein test results, it is better to determine the non-protein nitrogen content first and deduct its nitrogen contribution;
• The contribution of organic acids and ethanol to energy should be considered (e.g., sauerkraut with particularly high total acid, sweet wine brews containing acid and ethanol, etc.) Both organic acids and ethanol produce energy, and if not accounted for in the energy calculation, energy results are low;
• For condiments with a sodium content of 200% NRV or more, the sodium content should be appropriately lowered to create a more healthful condiment. Appropriate consideration can be given to making condiments with low sodium content.