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Behemoth
01-25-2004, 04:15 PM
How does the food companies or the government determine how many calories are in a given food? How do they know how many calories are in a cup of rice or an orange? And who does it? And how accurate really is it?


Also, along these lines... One brand of oats in the grocery store says that their oats have 150 calories per half cup, the other says per third of a cup. They're the exact same thing. Ground down to the same size. They're not the size of the quaker oats, but both offbrands that are slightly ground up.

raniali
01-26-2004, 12:42 PM
heat calorimetry
it is a simple test that measures the amount of heat released from a molecule/compound/substance upon burning. i do not know exactly why different brands have slightly different calorie contents except to conjecture that their quality control standards in the lab beg to be improved. additionally, measuring a solid on a volume basis is prone to more error than mass measurements.

Behemoth
01-26-2004, 12:50 PM
How do they determine how many grams of each macronutrient?

raniali
01-26-2004, 01:38 PM
since i do not perform lab analysis for food products, i can only speculate as to some of the methods used. there are many spectrophotometric options for determining mineral content. since fats are insoluble in water, it is likely they separate the fats from the bulk using extraction techniques. these can then be easily quantified and qualified. similar methods exist for carbs and proteins, salts and vitamins. take a look at the following link or the excerpts i pulled out that may shed some light on what is required in the food industry by the fda. the main link which may be of interest is : http://www.cfsan.fda.gov/~dms/lab-ind.html

http://www.cfsan.fda.gov/~dms/nutrguid.html


1. Characterizing the Product(s)

In characterizing the product, one should first determine the innate nutrient makeup of the product and obtain preliminary estimates of nutrient levels, nutrient variation, and the factors that could impact nutrient levels and variation. The first step in describing a product or products is to perform a literature search to determine if there are (1) existing nutrient data; (2) estimates that describe the market (production and sales); and, if appropriate, (3) information that describes the varieties (or species, if applicable); (4) the regions where the food is grown or raised; and (5) factors already studied and known to impact or not to impact nutrient levels. If the scientific literature and other sources reveal that a nutrient is known to be absent from the food or is present in negligible amounts (e.g., sugars and dietary fiber in seafood, cholesterol and saturated fat in produce), then the agency will not require testing for that nutrient, as long as the data base developer includes supporting documentation (58 FR 2079 at 2109, January 6, 1993).

If no information is available that adequately describes the food and its nutrients, the data base developer may choose to perform a pilot study to determine if certain factors do impact nutrient levels, to determine if there are regional differences in the nutrient levels, or to test for nutrient losses over time. In addition, the developer may choose to include other relevant factors of interest in a proposal to collect nutrient data for a data base study. For fruits and vegetables, variability may arise from seasonal and geographic influences associated with such factors as variety, location (e.g., soil type, climatic conditions); growing conditions (e.g., planting time, irrigation and fertilization practices, harvest maturity); product transport (e.g, packing, shipping, storage); and processing practices. For seafoods, the variability in nutrient levels may arise from such factors as species, dietary habits, processing practices, etc. For "mixed products", in addition to the factors that influence the variation in the nutrient levels in the product ingredients, processing factors associated with the formulation of the product ingredients into the "mixed product" may also influence the variation in the nutrient levels of the finished product. In some instances, if there is a great difference in nutrient values attributable to a particular factor (e.g., different nutrient values for different food types), a data base developer may determine that the foods are different and may even consider different nutrition labels for different food types.

When a data base developer submits a proposal to FDA, it is important to include the results of any pilot or experimental study that was completed. One data base developer, for example, completed a number of experimental studies that determined differences in nutrient levels between/among several independent variables (e.g., variety of food (2 levels), site of sampling (production vs. retail), packing medium (brine vs. water) , geographical region (5 levels), and age of product (5 levels)). FDA requests that the results of any experimental study that is submitted to the agency be included in statistical tables to better describe the type(s) of statistical test used, the sample size, and the exact probability levels that were used in drawing conclusions based on these results.

In determining the sampling plan (next section), existing nutrient data are extremely helpful in determining the number of samples to test.


It is well recognized that modifications of AOAC Official Methods may be needed to comply with labeling requirements because Official Methods are not currently available for all nutrients of interest in all food matrices. Sullivan and Carpenter identify acceptable AOAC Official Methods for a wide range of nutrients, the matrices for which the methods are applicable, and current ideas on method adaptations. With appropriate modifications, some AOAC methods that appear to be of limited applicability can be modified for use with other food matrices. Jeon and Ikins' text is a valuable resource that describes the Official Methods available for the mandatory nutrients required on the new food labels and also describes analytical procedures for many nutrients that are considered optional for food labeling. The text also discusses the analysis of hazardous contaminants in foods. These two references provide valuable information for those interested in analytical methods for nutrients in foods.

Jasonl
01-26-2004, 01:56 PM
since i do not perform lab analysis for food products, i can only speculate as to some of the methods used. there are many spectrophotometric options for determining mineral content. since fats are insoluble in water, it is likely they separate the fats from the bulk using extraction techniques. these can then be easily quantified and qualified. similar methods exist for carbs and proteins, salts and vitamins. take a look at the following link or the excerpts i pulled out that may shed some light on what is required in the food industry by the fda. the main link which may be of interest is : http://www.cfsan.fda.gov/~dms/lab-ind.html

http://www.cfsan.fda.gov/~dms/nutrguid.html
Took the words right out of my mouth.:D

raniali
01-26-2004, 02:05 PM
are you a chemist, too?

Podium Kreatin
01-27-2004, 03:40 PM
How do they determine how many grams of each macronutrient?

that's a good question. i always knew that macronutrients had standardized calories/gram, but i never thought how they knew how many grams of some food (esp natural products like wheat and fruit) is what.

Behemoth
01-27-2004, 04:24 PM
Can anybody shed any more light on this subject?

raniali
01-27-2004, 04:33 PM
what exactly do you want to know? are you interested in an complete and accurate lab manual for food extraction and measurement techniques?

Saint Patrick
01-27-2004, 04:43 PM
Don't trust the gub'ment!

Behemoth
01-27-2004, 05:58 PM
what exactly do you want to know? are you interested in an complete and accurate lab manual for food extraction and measurement techniques?

No, just something brief that gives me an idea, like your answer to how calorie content is determined.

Podium Kreatin
01-27-2004, 08:03 PM
No, just something brief that gives me an idea, like your answer to how calorie content is determined.

calorimetry, u burn something, then have something absorb that heat (water), then do some math calculation on how much heat is transferred (how much the water temp increases; its not one:one degree, every chemical has its own "specific heat")

Behemoth
01-28-2004, 02:12 PM
No, just something brief that gives me an idea, like your answer to how calorie content is determined.

That was regarding my question about determining how many grams of each macronutrient in a given food. But your info was helpful also, thanks PK.