Starch Inclusion Research Articles

Effect of treatment with sodium hydroxide on the feeding value of oat and rape straw for sheep

Oat and rape straws were treated with NaOH (70 and 40 g kg-1, respectively) by spraying with NaOH solutions (20 or 12.5% w/w), consolidating the sprayed straw into stacks, and storing under plastic. After storage for up to 60 weeks, in vitro digestibilities had been approximately doubled, although it appeared that the reaction was complete by 4 weeks. Potential digestibility of straw organic matter estimated by a polyester bag technique, was increased by c. 0.1 by NaOH treatment but the rate of digestion in the rumen was not changed. Following storage, treated and untreated straws were dried, ground, mixed with supplements and pelleted for feeding to sheep. Mixtures of treated or untreated oat straw, minerals, c. 3% urea and 0, 14, 28 or 42% starch were fed to mature wethers. The main effects of NaOH treatment of straw were to increase water intake, digestibilities of organic matter and cellulose, and rumen volatile fatty acid levels, and decrease rumen ammonia levels. Low intakes of NaOH-straw with no added starch were associated with high rumen pH (> 7.5 , probably due to unreacted alkali (equivalent to 23 g NaOH kg-1). Inclusion of starch, but not NaOH-straw treatment, improved dietary N utilization, although mean N balances were negative (- 5.5 to - 0.1 g day-1) on all diets. Feeding treated straw increased the amounts of Na eaten, and of Na and P apparently absorbed; the extra absorption was accounted for by increased urinary excretion so that retention was not increased. When diets of rape straw supplemented with urea and minerals were fed to 2-year-old wethers, NaOH treatment of straw increased intakes of food and water, organic matter digestibility, rumen volatile fatty acid concentration and N balance.

The effect of type and level of protein, fibre and starch on nitrogen excretion patterns in rats.

1. Three series of nitrogen balance experiments were performed with growing rats to test the effect of type and level of protein, fibre and starch on N excretion patterns. The design involved eighteen treatments in a 3 X 3 X 2 factorial experiment with five rats per dietary treatment. The eighteen treatments resulted from a combination of three protein treatments, three fibre treatments and two starch treatments. Protein treatments consisted of one level (15 g N/kg DM) of casein fortified with methionine, a protein of high digestibility, and two levels (15 and 20 g N/kg DM) of autoclaved brown beans (Phaseolus vulgaris), a protein source of low digestibility. The fibre treatments were two levels of cellulose powder and one level of barley hulls. The two starch treatments were autoclaved potato starch and autoclaved and raw potato starch (1:1, w/w). 2. The inclusion of raw potato starch reduced true protein digestibility markedly when the protein source was casein, but the corresponding biological values were increased significantly with this treatment. This strongly indicated a movement of urea from the blood to the intestines. This assumption was also supported by significantly lower blood urea concentrations in animals given raw starch. The influence of raw starch on true protein digestibility was, however, significantly less when cellulose and barley hulls were included. This is probably due to reduced transit time from fibre inclusion. The nature of the gut contents also supported this hypothesis. 3. The inclusion of raw potato starch when brown beans were the source of protein had much less effect on true protein digestibility and biological value than when casein was the protein source. This was probably due to the low digestibility of DM and protein in this food leaving sufficient energy and protein for maximum microbial growth. The inclusion of fibre also had little effect on N excretion patterns with the brown-bean diets. 4. An increase in the level of brown bean inclusion reduced true protein digestibility only on the diets containing raw starch whereas the biological value was consistently reduced regardless of starch treatment. The lower biological values were associated with significantly higher blood urea concentrations. Increasing the level of brown bean inclusion also resulted in higher fresh weights of caecum, colon and contents. 5. The present work proves that, through dietary manipulation, it is possible to affect nitrogen excretion patterns in rats.

Structural and functional aspects of stomata

Differential cell wall thickening in developing guard cells of Polypodium vulgare L. has been studied with particular reference to guard cell protoplast deformation and the eventual formation of the stomatal pore. Concomitant studies on the development of guard cell chloroplasts and their starch inclusions during ontogeny of the stomatal complex have provided data which have been incorporated into a model to account for the formation of the pore. Guard cell starch inclusions reach a maximum density per unit volume at the same time as the guard cell walls achieve maximum differential thickening. These events coincide with the development of the pore. It is suggested that, whilst pore formation is initiated enzymatically, the mechanical forces required to bring about the separation of the two guard cells are of an osmotic nature derived from starch hydrolysis. The development of the mesophyll in relation to the epidermis is examined in respect of the formation of substomatal chambers.

Determination of the Tryptophan Content of Proteins by Ion Exchange Chromatography of Alkaline Hydrolysates

Abstract A study of the variables in techniques for alkaline hydrolysis of proteins and for chromatographic analysis of the products has led to a method for the accurate determination of tryptophan. Quantitative recoveries of tryptophan are obtained when proteins (1 to 5 mg) are hydrolyzed at 110° or 135° in 0.6 ml of 4.2 n NaOH containing 25 mg of starch. The hydrolysis is performed in polypropylene liners sealed inside glass tubes evacuated to below 50 µm of mercury. Ion exchange chromatography of tryptophan on Beckman PA-35 resin (column height 8 or 12 cm) has been accomplished in 30 to 50 min with pH 5.4 buffer, 0.21 n in Na+. The details in the procedure which make possible complete recovery of tryptophan include: (a) addition of the sample at pH 4.25 instead of at pH 2.2 in order to avoid loss of tryptophan in citrate buffer at acid pH; (b) the use of NaOH instead of Ba(OH)2 to avoid loss of tryptophan by adsorption on BaSO4 or BaCO3; (c) the inclusion of starch as the most effective antioxidant tested; and (d) chromatography with a buffer which separates tryptophan from Ne-(dl-2-amino-2-carboxyethyl)-l-lysine, which can be formed in significant quantities during alkaline hydrolysis. Molar calculations of protein concentrations are based on the results from analysis of an acid hydrolysate run parallel with the alkaline hydrolyses. Integral values (100 ± 3%) have been obtained for the expected number of tryptophan residues in tryptophyl-leucine, human serum albumin, porcine pepsin, sperm whale apomyoglobin, and in bovine α-chymotrypsin, trypsin, deoxyribonuclease, and serum albumin. Since carbohydrate does not interfere, the procedure is applicable to foods and has been tested on normal and opaque-2 maize meals and on wheat flours.

An Improved Nonselective Culture Medium for Ruminal Bacteria and Its Use in Determining Diurnal Variation in Numbers of Bacteria in the Rumen

Summary An improved rumen fluid agar medium was developed that permitted the growth of about double the numbers of bacteria from ruminal contents grown in the medium previously used. It allowed much larger numbers of colonies to be counted and isolated with greater ease from a given volume of medium and after longer incubation periods. The main modifications made were the use of rumen fluid clarified by centrifugation, reducing the concentration of the sugar energy sources (glucose and cellobiose) and inclusion of soluble starch as an additional energy source, and changing the reducing agent from cysteine to a combination of cysteine and sodium sulfide. Many other modifications in the medium were tested and found to be without effect or detrimental to colony counts. Experiments indicate that about the same range of species of bacteria are cultured in the improved medium as in the old, except that the improved medium allows the growth of bacteroides strains that utilize starch but not glucose or cellobiose. Significant differences were shown in nonselective viable counts of ruminal bacteria obtained from samples of rumen contents collected at different times during the day from a cow fed alfalfa hay or a grain mixture once a day, and there were also differences in counts due to the ration.

The development of adult cell form in Pediastrum biradiatum Meyen as revealed by the electron microscope

An electron-microscope study was made of thin sections of cells from several developmental stages involved in the transformation of the motile zoospore into the four-pronged adult cell type during asexual reproduction in Pediastrum biradiatum Meyen. The various stages were obtained by separating swarmers from adult colonies using fine nickel screening and allowing progressively longer periods of zoospore change before fixing in OsO4. Early adult stages were obtained by fixing cultures after approximately 6 hours of swarmer production. Chloroplasts are observed in cells from all developmental stages. No grana, typical of the chloroplasts of higher plants, are discernible, but a lamellar structure is present and the chloroplast is limited by a double membrane. The chloroplasts contain low density starch inclusions and small, dense inclusions, similar in texture and density to large, dense, spherical bodies which occupy a considerable proportion of the cell volume. The significance of the latter bodies is unknown, but reference is made to their possible role in cell-wall formation. Pyrenoid bodies are not present in any recognizable form until the adult cell type is achieved and appear to develop from the chloroplast. The pyrenoid appears homogeneous and is nearly surrounded by starch plates in the mature forms. The cell wall develops from a thin, membranous covering into a thickened structure containing a globular network. The latter is found in the early adult stages. A small amount of endoplasmic reticulum is present and a Golgi apparatus which in some instances resembles the Golgi forms of higher animals and in other cases is similar to the dictyosomes of protozoa and invertebrates. The nucleus, which is often nearly rectangular in profile, is enclosed by a double membrane which in some cases appears to have an intimate association with the Golgi apparatus. The mitochondria are very few in number and possess only a few randomly oriented cristae. Large vacuoles are described which contain secondary double-membrane limited vacuoles in addition to inclusions similar to those found in the cytoplasm.

Coeliac Disease: A Relation between Dietary Starch and Fat Absorption

In a previous communication (1948) reasons were given for regarding starch intolerance in children with coeliac disease as perhaps of greater etiological importance than the well known failure to absorb the products of fat digestion. These reasons were (1) coeliac disease usually begins between six months and two or thred years of age, and during infancy, at a time when their diet, consists of milk, the children who eventually develop this disorder show no indication of what is to come. It is clear that the constituents of milk present no difficulty to the infant who later develops coeliac disease. (2) The principal dietetic change that occurs during the age when coeliac disease becomes manifest consists of a steadily increasing intake of starches. (3) Abdominal distension, which is so constant a characteristic of coeliac children, is not exhibited to any noteworthy degree in infants who for other reasons are intolerant solely of fat, and in coeliac children this feature is much more attributable to fermentation of carbohydrate than to unabsorbed -fat. Assuming that intolerance of starch exerts a primary etiological role in coeliac children, and that failure to absorb fat is a secondary consequence dependent in some way upon mismanagement of starch, it might be possible to improve fat absorption by eliminating starch from the diet, always provided that the failure of fat absorption does not so alter. conditions in the intestine that once this failure has developed it then persists by its own mechanism. It was decided to put this matter to trial by feeding coeliac children on two consecutive diets, both containing an ample portion of fat, the first diet containing starch and the second being free of starch, and to compare the absorption of fat from each diet by means of fat balances. It was soon *evident that fat absorption was much improved on a diet free from starch. The investigation was then reversed, beginning with a starch-free diet and later changing to one containing starch; again it was demonstrated that the inclusion of starch in the diet lowered the absorption of fat. Experiments on these lines have been conducted on fifteen children with coeliac disease, and the results, which are set out in table 1, form the basis of this communication.