Sterol content of foods of plant origin.

Available data on phytosterols from the world's literature have been compiled and summarized. There still exists a paucity of data on the quantities of plant sterols in many foods. More extensive data are available on the relative sterol composition. Our compilation shows that plant oils are excellent sources of phytosterols. Nuts and seeds contain moderate levels, and fruits and vegetables generally contain the lowest concentrations of plant sterols. Analyses of the minor sterols, namely, the delta5- and delta7-phytosterols, have become available only recently.

Vitamin E content of foods.

Tables showing representative values for the vitamin E content of human foods have been developed from all the available reliable information. These tables cover animal products, plant products, fats and oils, baked products, infant foods, and mixed dishes. The effects on vitamin E content are discussed for heating and storage of dairy products, grains, vegetables, and plant oils; for the refining of plant oils; and for the processing and baking of grain products. Causes of variation in vitamin E levels are presented and the distribution of the different forms of vitamin E in foods is shown. The biologic activities of these forms are used to calculate approximate vitamin activity values of representative foods.

Comprehensive evaluation of fatty acids in foods.

Based on production volume and value and on per capita consumption, shellfish are an important food group in the United States. The nutrient composition of shellfish indicates that this food group is low in fat and relatively high in protein. Tabulated data on fatty acids in the different edible portions of seven species of crustaceans and over twenty species of mollusks are presented. The proportionately high level of polyunsaturated fatty acids is shown by the polyunsaturation index calculated for some important species of shellfish.

Comprehensive evaluation of fatty acids in foods. IX. Fowl.

An extensive survey of the post-1960 literature on the lipids of fowl has been completed. This review shows that the total lipid content of chicken tissues increases with age. The fatty acid composition of both chicken and turkey tissues reflects the fatty acid composition of the dietary fat. The fatty acid composition data for dark meat, light meat, or skin of all classes of chicken --broiler-fryer, roaster, and stewing hen--raised on diets equivalent to commercial feed were combined into single tissue-type fatty acid profiles. Similar profiles were also established for roaster-fryer turkey, young tom turkey, and young hen turkey. Breed, sex, and environmental temperature showed only minor effects on the tissue fatty acid compositions. Young chicken flesh contains less fat than that of stewing hens, turkeys, and other fowl, which all have approximately equal total fat content. White meat of chicken and turkey contains the least amount of fat, and the skin of all birds contained the largest amount, duck and goose skin containing the greatest of all. Tables of the total fat and fatty acid composition of tissue and tissue composites of fowl are given. Studies on chicken and turkey tissues were sufficiently numerous that the computed fatty acid compositions in the tables are considered reliable representation of market birds. Data for goose, duck, partridge, pheasant, pigeon, and quail were computed from sparse information and should be viewedas provisional guides.

Comprehensive evaluation of fatty acids in foods. VIII. Finfish.

Recent (since 1960) data on the lipid content and fatty acid composition of fish were surveyed as part of the continuing USDA program to provide information on the nutrient composition of foods. Tabulated values of total lipid and fatty acids in finfish are presented. The most prominent fatty acids occurring in finfish are palmitic (C16:0), C18:1 (in some species C20:1 and C22:1), and the highly polyunsaturated C20:5 and C22:6. The general nutritional value of finfish is discussed. Two measures of polyunsaturation are presented for some commercially important domestic finfish: the total amount of polyunsaturated fatty acids (PFA) and the relative degree of polyunsaturation (PI).

X. Lamb and veal. Comprehensive evaluation of fatty acids in foods.

As a result of critical review of information on lipid composition of foods, representative values have been derived for the lipid and fatty acid contents of lamb and veal. Comprehensive tabulations of fatty acids in 100-gm. portions of raw and cooked retail cuts are given. The mean fatty acid profiles of the lean and adipose tissues which were used for computing the fatty acid values in the food tables are presented. The lean tissue lipid of lamb contains a significant amount of caprylic, arachidic, and arachidonic acids which are not present in the adipose tissue. A comparison of beef and veal shows that veal lipid is a richer source of polyunsaturated fatty acids. The new values presented here for fatty acids in lamb and veal should provide nutritionists and dietitians better means for evaluating diets.

Comprehensive evaluation of fatty acids in foods. VI. Cereal products.

Information on total lipid and fatty acid composition or cereal grains and their products used for food has been collated in a comprehensive search of world literature published since 1960. Data considered most suitable for use for representing contents of total lipids and fatty acids have been tabulated and are presented. In developing these data, attention was given to stability and other chemical properties of the lipids, lipid composition of the different parts of the grain, and to such factors as genetics, production, processing, and analytical methods used in extracting and determining the fat and fatty acids in cereal products.

Comprehensive evaluation of fatty acids in foods. V. Unhydrogenated fats and oils.

This paper summarizes representative values for the fatty acid composition of unprocessed vegetable fats, vegetable oils, and animal fats. The data for these unprocessed fats and oils are identical with those of the processed, but unhydrogenated fats and oils. Calculations to convert the fatty acid methyl ester data to grams fatty acid per 100 gm. food are discussed, and the converted data are presented in tabular form. Climatic and cultivar effects on the fatty acid composition of some of these oils are reviewed.

Comprehensive evaluation of fatty acids in foods. IV. Nuts, peanuts, and soups.

As part of USDA research to provide reliable and up-to-date tabulations of lipids and fatty acids in foods, representative values have been derived and tabulated for nuts and commercially canned condensed soups. Except for palm-type nuts, unsaturated fatty acids are the major acids in nuts; oleic acid is generally the predominant unsaturated fatty acid. The new fatty acid values indicate greater concentrations of saturated fatty acids than previously reported. The P:S ratios for nuts and peanuts are presented. The fatty acid contents of soups are varied and reflect the lipid composition of the source(s) of fat of the particular ingredients used in the manufacture of these products. These new values for fatty acids in nuts and soups should greatly help nutritionists and dietitians to better assess the total contribution of each particular fatty acid to the diet.

Heats of combustion of chemically different lipids.

The caloric content of foods listed in food composition tables, such as the USDA Agriculture Handbook No. 8, is calculated by multiplying the gram amount of the protein, fat, and carbohydrate in the food by specific caloric factors derived around the turn of the century by Atwater and co-workers. To evaluate the accuracy of these specific caloric factors, we determined the heats of combustion of vegetable oils as purchased; of lipids extracted from red meats, chicken, fish, egg yolk, and cereal grains; and of the residue (protein) left after lipid extraction of the meats. These heats of combustion were converted to available energy values by the method of Atwater . The specific caloric factors used to calculate the caloric content of foods in Agriculture Handbook No. 8 and other tables of food composition may exaggerate the calories contributed by the lipids in some foods. When the food lipid was mainly triglyceride, the available energy values calculated in this study were within 2% of the specific factors used in Agriculture Handbook No. 8. However, when the food lipid had a high content of phospholipid, our calculated available energy values were lower than the specific factors used currently. The energy content of the fat-free residue (protein) of meat, poultry, and fish was also less than that currently used for those foods in food composition tables.

Summary of available data for cholesterol in foods and methods for its determination.

A search of the literature has been conducted on the cholesterol content of foods and on the methods for its determination. The amount of cholesterol in food is important because of its possible relationship to the onset of atherosclerosis in humans. Cholesterol is present primarily in foods of animal origin. The main sources in the American diet are eggs, poultry, dairy products, fish and seafood, and meat products. Only a few samples of these products have been analyzed. In many cases there is a wide range in cholesterol values for samples analyzed. Much of the research was conducted many years ago. The most commonly used methods were gravimetric or colorimetric. In many cases the samples investigated were not adequately described. Cholesterol was often determined without isolating it from interfering materials. Although some of the cholesterol values reported in the literature appear to be reasonably accurate, there is an urgent need for reinvestigation of the cholesterol content of foods using more recently developed methods of analysis.