Resistant starch: Variation among high amylose rice varieties and its relationship with apparent amylose content, pasting properties and cooking methods.

Resistant starch (RS), which is not hydrolyzed in the small intestine, has proposed health benefits. We evaluated 40 high amylose rice varieties for RS content in cooked rice and a 1.9-fold difference was found. Some varieties had more than two-fold greater RS content than a US long-grain intermediate-amylose rice. The high amylose varieties were grouped into four classes according to paste viscosity and gelatinization temperature based on genetic variants of the Waxy and Starch Synthase IIa genes, respectively. RS content was not different between the four paste viscosity-gelatinization temperature classes. Multiple linear regression analysis showed that apparent amylose content and pasting temperature were strong predictors of RS within each class. Two cooking methods, fixed water-to-rice ratio/time and in excess-water/minimum-cook-time, were compared using six rice varieties that were extremes in RS in each of the genetic variant classes, no difference in RS content due to cooking method was observed.

Effects of dietary sweet potato leaf meal on the growth, non-specific immune responses, total phenols and antioxidant capacity in channel catfish (Ictalurus punctatus).

BACKGROUND: Traditional energy sources in catfish diets have become costly, and economical alternatives are needed. Sweet potato leaves are underutilised agricultural by-products that provide energy and substantial amounts of phenols, which affect animal and human health. There is little information on the effects of these compounds on catfish, or the capacity of catfish to accumulate dietary phenols. Catfish enriched with phenols have marketing potential as functional foods. This study investigated the effects of diets with sweet potato leaf meal (SPLM) on growth performance, health and total phenolic compounds in catfish. RESULTS: SPLM was substituted for wheat middlings in three diets fed to groups of juvenile catfish for 10 weeks. Weight gain, feed conversion, survival, alternative complement activity and lysozyme activity were similar among diets. Haematocrit was lower in fish fed diets with SPLM, but within the normal range. Total phenols and antioxidant capacity in the whole body were similar among treatments. CONCLUSION: SPLM was an effective energy source for catfish up to the maximum level tested (230 g kg(-1) diet). SPLM did not enhance total phenols in catfish, but there were no apparent antinutritional effects of the meal on catfish growth, health or survival.

Thorough study of reactivity of various compound classes toward the Folin-Ciocalteu reagent.

A thorough study was done to test the reactivity of the Folin-Ciocalteu (F-C) reagent toward various compound classes. Over 80 compounds were tested. Compound classes included phenols, thiols, vitamins, amino acids, proteins, nucleotide bases, unsaturated fatty acids, carbohydrates, organic acids, inorganic ions, metal complexes, aldehydes, and ketones. All phenols, proteins, and thiols tested were reactive toward the reagent. Many vitamin derivatives were also reactive, as were the inorganic ions Fe(+2), Mn(2+), I(-), and SO(3)(2-). Other compounds showing reactivity included the nucleotide base guanine and the trioses glyceraldehyde and dihydroxyacetone. Copper complexation enhanced the reactivity of salicylate derivatives toward the reagent, whereas zinc complexation did not. Several amino acids and sugars that were reported to be reactive toward the F-C reagent in earlier studies were found not to be reactive in this study, at least in the concentrations used. Reaction kinetics of each compound with the F-C reagent were also measured. Most compounds tested showed a biphasic kinetic pattern with half-lives under 1 min. Trolox and ascorbic acid displayed a rapid monophasic pattern in which the reaction reached end point within 1 min. In summary, this study has shown that the F-C reagent is significantly reactive toward other compounds besides phenols. As other investigators have suggested, the F-C assay should be seen as a measure of total antioxidant capacity rather than phenolic content. Because phenolics are the most abundant antioxidants in most plants, it gives a rough approximation of total phenolic content in most cases.

Comparative reaction rates of various antioxidants with ABTS radical cation.

The reaction rates of several aminothiol, amidothiol, and phenolic antioxidants with ABTS radical cation were measured. Most compounds had half-lives of less than one minute. However several compounds had considerably longer half-lives. Aminothiol derivatives lacking a free thiol group, such as amifostine and RibCys, displayed longer half-lives. Reaction of these compounds with the ABTS radical cation displayed first order kinetic behavior. Of the phenolic compounds studied, chlorogenic acid and caffeic acid had the longest half-lives. Most phenolics displayed a biphasic kinetic pattern involving fast and slow steps. Some of the aminothiols also displayed this type of behavior. Glutathione disulfide was reactive toward ABTS radical cation and displayed slow kinetics. This suggests that the slow step observed with some of the aminothiols may be due to initial rapid formation of disulfide followed by slow reaction of the disulfide with ABTS radical cation. Some compounds required a considerably longer incubation time to reach end point than the six to ten minute period normally used for this assay. This suggests that, when ABTS is being used as an end point assay, a longer incubation time may be needed to obtain reliable data. When food substances are being tested using this assay, kinetic profiles should first be examined before end points are determined. This paper contains the first published data reporting antioxidant capacities of amino- and amidothiols measured by the ABTS method.