Energy Value of Resistant Starch

Resistant starch was evaluated for energy value using fine silica and normal starch as controls and young rats as a test model. The net increase in rats' carcass energy due to the test materials fed over a 3-wk period formed the basis for assessing energy value. Rats fed normal starch deposited about twice as much fat and significantly more protein in the carcass than those fed either resistant starch or silica. Rats fed resistant starch or silica showed similar growth responses and increases in components of body composition and carcass energy content. This suggested that resistant starch provided, like silica, no energy.     

Iron-Enriched Bread: Interaction Effect of Protein Quality and Copper on Iron Bioavailability

These studies examined the bioavailability of iron in iron-enriched breads. The test breads also contained added protein in the form of gluten, soy or nonfat dry milk. Bioavailability was assessed based on net hemoglobin synthesis in rats initially made iron deficient and then fed bread-based diets containing 38.5 ppm iron (NRC requirement for rat, 35 ppm) and 3.75, 5.00, or 6.25 ppm copper (NRC requirement for rat, 5 ppm). More hemoglobin was synthesized on milk-supplemented (83 mg/mg iron) and on soy-supplemented (85 mg/mg iron) bread diets than on gluten-supplemented (59 mg/mg iron) bread diets. Copper appeared to have no influence on hemoglobin regeneration or on hepatic iron accumulation under the conditions of this experiment.     

B Vitamins in Selected Variety Breads Commercially Produced in Major U.S. Cities

Three enrichment vitamins (thiamin, riboflavin, niacin) and three other (folic acid, pantothenic acid, vitamin B₆) B vitamins were determined in 10 types, up to four brands of each type, of variety breads (including tortillas) purchased from four major U.S. cities. In general, bread types traditionally enriched and not containing nonflour components as significant ingredients met the vitamin enrichment standards. In many products, the contents of all six vitamins varied appreciably from brand to brand. In contrast to wholewheat bread and some enriched breads, corn tortillas were consistently low in ail vitamins except vitamin B₆.     

Distribution of Total and Soluble Fiber in Various Millstreams of Wheat

Twenty-three mill flour streams, four final flours, germ, millfeed and three millfeed fractions from milling hard red wheat were analyzed for soluble fiber (SF) and insoluble fiber (IF). The objective was to identify a fraction(s) that may be a good source of SF. Whole wheat flour and germ each contained about 10% total (IF + SF) fiber; they also matched closely in SF and IF. Excluding the red dog fraction, the bran fraction was highest in SF. SF represented about 5% of the total fiber in the bran. No flour stream was a particularly good source of SF. The sixth middlings stream had about one-fourth of the total fiber as SF. Other streams, as well as “straight” and “patent” flours, contained SF and IF in about equal amounts. Products with straight or patent flour would increase SF in the diet without a disproportionate increase in IF.     

Effect of Mineral Gluconates on Quality Characteristics of Bread and Cookies

These studies examined the effect of expanded fortification (FNB, 1974), using gluconates of Fe, Zn, Ca, and Mg as the mineral source, on quality characteristics of white pan bread and chocolate chip cookies. Gluconates, including magnesium gluconate, did not affect the yeast activity, dough mixing time, proof time, or dough pH. The pH and subjective quality scores of the breads were also little affected by any of the gluconates. Fortification reduced the specific loaf volumes slightly and also caused, by day 6, a greater firming of the crumb. Gluconates did not affect the subjective quality scores or spread ratios of the cookies, although cookie pH was lowered somewhat. Used singly, test gluconates did not appreciably alter the bread or cookie flavor profile except that cookies containing Zn gluconate were consistently preferred.     

Energy Value of a Fat High in Stearic Acid

A fat containing 92.1% stearic acid (tristearin) was evaluated for energy value using shortening (9 kcal/g) and mineral oil (0 kcal/g) as controls and young rats as the test model. Energy value was calculated based on efficiency of conversion of estimated gross energy intake to carcass energy over a 3-wk period. Rats fed the shortening-based diet deposited more than double the fat and significantly more protein in the carcass than rats fed the tristearin-based diet. Rats fed the tristearin-based diet deposited significantly more fat and protein than rats fed the mineral oil-based diet. Based on these observations, the estimated energy value of tristearin was calculated as 3 kcal/g.     

Effect of Calcium Level on Bread Iron Utilization by Iron-Deficient Rats

Utilization of iron in bread containing variable amounts of calcium was examined using iron-deficient rats as the test model. Iron was added to the bread at the normal enrichment level. Calcium, however, was added at levels up to 9 times the normal level. Iron utilization efficiency (IUE) was calculated based on collective increases observed in hemoglobin and liver iron. Compared to a diet low in both calcium and phosphorus (IUE = 100%), IUE averaged 98% when the diet was high in calcium but moderate in phosphorous, and 78% when the diet was very high both in calcium and phosphorous. Viewed collectively, the data suggested that excessive intake of both calcium and phosphorus would adversely affect the utilization of iron in bread, but some excess of calcium alone would not.     

Effect of the Source of Fiber in Bread-Based Diets on Blood and Liver Lipids in Rats

Fiber in 12 types of breads was tested for effect on blood and liver lipid levels in normolipidemic young rats. Breads provided the same, 4.I%, level of total, but variable levels of soluble, fiber in the diets. Over one-fifth of the total dietary fiber in corn tortillas, oatmeal bread, white bread and two multigrain breads containing vegetable powder was soluble fiber. Diet based on white bread was the only 100% bread diet; sucrose was added to the other 11 diets to equalize the content of available carbohydrates. Results showed that soluble fiber was negatively correlated with seturn cholesterol (r, ?0.38) and serum triglycerides (r, —0.36) but positively correlated with:liver cholesterol (r, 0.53); the reverse was true for three other experimental variables, namely sucrose and casein added to the diets and weight gains of the animals. This latter observation apparently negated, to some extent, the hypolipidemic effect of certain bread types tested.     

Bioavailability of Iron in Iron-Fortified Fluid Milk

The bioavailability of iron in pasteurized and homogenized cow's milk was determined by the hemoglobin depletion-repletion technique using rats. A water soluble citrate phosphate iron complex (iron, 16.67%) was used to fortify milk (iron, 38 ppm). Results showed that iron in milk was as well available as that in ferrous sulfate (99% vs 100%); the same was true when the iron complex was tested as such (not added to milk). Thus, milk or milk components appear not to adversely affect the bioavailability of added iron under the conditions of this experiment.