Browsing by Subject "starch"
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Item Effects of carbohydrate applications on growth and vitality of live oak (Quercus virginiana)(2009-05-15) Martinez Trinidad, TomasUrban forests grow in stressful environments that can have negativerepercussions on tree energy reserves. The goal of this research was to evaluate theimpact of exogenously applied carbohydrates on growth and vitality of live oaks(Quercus virginiana P. Miller). An initial study focused on carbohydrate partitioningrevealed that annual mean glucose concentration in leaf tissues (49.55 mg?g-1 DW) wasalmost double that in twigs, trunks, or roots. Starch concentrations in roots and trunks(38.98 and 38.22 mg?g-1 DW of glucose, respectively) were higher during the dormantseason and approximately three times the concentrations found in other tissues. Aninvestigation of the effects of exogenous soil applications of glucose and starch on soilmicrobial activity revealed no significant differences using recoverable viable microbes.However, soil respiration was significantly increased (P<0.05) by glucose a week afterapplication, while higher starch concentrations (120 g?L-1) significantly increased(P<0.05) soil respiration after the fourth week. Although tree soil drenched withcarbohydrates in a different study showed significantly (P<0.05) greener leaf color, higher chlorophyll fluorescence, and increased soil respiration at higher concentrationsof starch (120 g?L-1), no significant differences were observed in photosynthesis or trunk,canopy, or root growth. Analysis of 13C signatures was unable to detect uptake ofexogenous carbohydrates. For trunk-injected trees with glucose and sucrose, trunkgrowth was significantly (P<0.05) increased by carbohydrate supplementation.Differences were also found in twig glucose content, root starch content, and chlorophyllfluorescence among overall concentration means. A study to compare field diagnostictools with carbohydrate laboratory analysis established that a portable blood glucosemeter can be used to measure glucose content in trees. However, ohmmeter,refractometer, chlorophyll fluorescence spectrometer, and iodine staining results did notcorrelate well with laboratory analysis of carbohydrate concentrations. Results fromthese studies reveal that soil applied carbohydrates can greatly increase soil microbialactivity, provide evidence that trunk-injected carbohydrates may improve growth andvitality of live oaks, and provide a new field diagnostic tool to increase the efficiency ofmeasuring carbohydrates in trees.Item In vitro starch digestibility and estimated glycemic index of sorghum products(Texas A&M University, 2007-09-17) De Castro Palomino Siller, AngelinaFractions from white and tannin sorghums were processed into extrudates, thick porridges, and breads. The effects of sorghum type and fraction on the in vitro starch availability of the products were evaluated, and the estimated glycemic indexes (EGI) of the products were obtained. Sorghum extrudates were significantly more slowly digested than corn meal extrudates for all preparation methods (whole, cracked and decorticated kernels). Furthermore, tannin extrudates were less digestible than white sorghum extrudates. The soft endosperm nature of the tannin sorghum limited friction formation inside the extruder, reducing starch gelatinization. On the other hand, condensed tannins also interfered with the starch availability for digestion. White sorghum was more 'suitable' for extrusion, giving extrudates with higher starch degradation and expansion than the tannin sorghums. However, tannin sorghums also gave acceptable products offering the benefit of lower EGI values. Sorghum porridges were more slowly digested than a corn flour porridge when using whole and decorticated flours. In addition, tannin sorghum porridges had a lower starch digestibility compared to all the samples. Tannin sorghum flours produced soft porridges with enhanced initial starch digestibility. However, condensed tannins seemed to offset the starch digestion by limiting starch availability. All sorghum porridges had significantly lower EGI values than the corn porridge. Extrudates and porridges had reduced starch digestibilities and EGI values when using whole grains compared to using the decorticated fractions. This was observed in both the white and the tannin sorghum. Therefore, whole-grain products from sorghum have health benefits attributed to whole grain foods and slower digesting starches; for instance, prevention and treatment of diseases such as diabetes, insulin resistance, obesity, cardiovascular disease, and some types of cancer. When 12% of tannin bran was added to a wheat bread formulation, a slower rate of starch digestion was observed compared to a wheat bread. The high concentration of non-starch components of the bran (i.e. dietary fiber, condensed tannins) affected starch digestion. The addition of tannin sorghum bran significantly reduced the EGI value of wheat bread, besides being a natural source of brown color, and an excellent source of antioxidants and dietary fiber.Item Influence of exogenous effectors of invertase activity on rice physiology and growth(2009-05-15) Rounds, Elliott WilsonCarbon flow into developing ovaries has been reported to be important in seed retention and seed size. Invertase, which cleaves sucrose into glucose and fructose has been shown to be important in rapidly expanding tissue, such as early root growth or during tiller expansion. The manipulation of invertase activity with over-the-top applications of agrochemicals may prevent the detrimental effects of abiotic stress by altering the source/sink relationship. These experiments examined economically important tissues in rice production during critical developmental stages under abiotic stress. Field and greenhouse studies were conducted under normal growing conditions using local management practices. Plants were treated with exogenous chemicals that affect the activity of invertase during the early-grain fill stage on field grown plants. Other plants were exposed to elevated nighttime temperature of 30?C for 4 d using a free-air, infrared heating device in the greenhouse. Rice was also treated at mid- to late-grain fill stage of the main crop to identify the impact of the exogenous chemicals on developing ratoon tiller buds. The activity of soluble acid invertase (SAI), concentrations of glucose, fructose, sucrose, and starch were determined in penultimate leaves, panicles, and main-crop stem segments during ratoon tiller bud expansion, using the enzyme-coupled stoichiometric production of NADH measured spectrophotometrically at 340nm. The results suggest SAI, carbohydrates, and agronomic characters are influenced by exogenous chemicals at the applied rates. The thidiazuron treatment caused an unidentified stress event. The stress was confirmed by increased hexose concentration and the proportion of hexose concentration to sucrose concentration. This stress reduced the main-crop grain yield, but not the ratoon yield or total grain yield. An interaction between the ammonium molybdate treatment and high nighttime temperature was seen in the panicle. The ranked difference was reduced by the high nighttime temperature from the ambient nighttime temperature for the SAI activity, TSC content, starch content, and TNC content. The tested chemicals and rates are not appropriate for commercial rice production because the effect of the exogenous chemicals do not appear to consistently aid rice plants to counteract the detrimental effects of abiotic stress.Item Roles of carbohydrates and proteins in the staling of wheat flour tortilla(2009-05-15) Alviola, Juma Novie AyapEffects of enzymatic modification of starch, proteins and pentosans on dough and tortilla properties were determined to establish the role of these wheat components in tortilla staling. Starch, protein and pentosans were respectively modified with a-amylase, protease and transglutaminase (TG), and xylanase. Tortillas were stored at 22oC and evaluated for at least three weeks. Amylase improved shelf-stability of tortillas, produced a significant amount of dextrins and sugars, retarded decrease in amylose solubility, and weakened starch granules. However, control and treated tortillas had similar degrees of amylopectin crystallinity. Staling of tortillas appears to involve starch that reassociates into an amorphous structure. Micrographs of control dough had thin protein strands forming a continuous matrix. Protease-treated dough had pieces of proteins in place of the continuous matrix, while TG-treated dough had thicker protein strands that were heterogeneously distributed. Both treatments resulted in shorter shelf-stability of tortillas. The organization of protein in dough is important for dough structure and appears to impact tortilla flexibility. Protein solubility and SDS-PAGE results did not differentiate control and treated dough or tortillas. The fractions or molecular weight distribution are not significant determinants of protein functionality. Tertiary and quaternary protein structures of gluten may be more related to tortilla shelf-stability. The 75 ppm xylanase treatment resulted in weaker tortilla structure and significantly higher amounts of low molecular weight saccharides and sugars. Control and the 25 ppm treatment sample had a similar shelf-stability and texture profile. Pentosans may affect staling indirectly through the effect on gluten development. Fresh tortillas have amylopectin in an amorphous state, while amylose is mostly retrograded. The gluten matrix provides additional structure and flexibility to the tortilla. Pentosans may or may not be attached to the gluten network. Upon storage, amylopectin retrogrades and recrystallizes, firming the starch granules, resulting in firmer tortillas. Starch hydrolysis decreased the rigid structure and plasticized polymers during storage. It also reduced the restriction imposed by retrograded starch on gluten and allowed it more flexibility. Thus, the flexibility of tortillas results from the combined functionalities of amylose gel, amylopectin solidifying the starch granules during storage, and the changed functionality of gluten after baking.Item The Effect of Dietary Starch Concentration on Glycogen Replenishment in Performance Horses(2013-12-12) Vonderohe, CaitlinFour Quarter Horses (2 to 3 yr; 401 to 432 kg BW) were used in a simple crossover design for a 49-d study to determine the effect of dietary starch levels on post-exercise glycogen replenishment. Horses were fed either high starch (HS) or low starch (LS) concentrates at 0.75% BW/d plus l.0% BW/d Coastal Bermudagrass hay for 14 d, and then worked to fatigue in a standardized exercise test (SET). After a 14-d washout period, horses were switched to the opposite diet for 14 d and then again performed the SET. The LS and HS concentrates were commercially available feeds. Total diets provided an average of 997.6 g of starch and 553.7 g of starch/d in the HS and LS diets, respectively. Throughout the trial, horses were lightly exercised for 30 min, 3 d/wk. The SET consisted of a 30-min warm-up period at a brisk trot in a panel exerciser, followed by 27 min of gradually ascending high-intensity work on a treadmill. Skeletal muscle biopsies were taken from the biceps femoris at rest, immediately after the SET, and again at 6-, 24- and 48-h post-exercise. Samples were flash frozen in liquid nitrogen and stored at -80?C until analysis for later muscle glycogen concentration using a commercial kit. Venous blood samples were taken at rest, immediately post exercise and every 15 min for 3 h post-exercise. Blood samples were analyzed for lactate, glucose, total protein and Ca concentration. Data were analyzed using Proc Mixed (SAS) procedure with main effects of sample time, horse, period, trt and time x trt interaction. Horses on the HS diet had a higher muscle glycogen concentration (P <0.05) at 48 h post exercise than the LS horses (18.1 vs. 10.6 ?g/mg wet wt). At 6 h, HS horses had a more rapid rate of repletion, as observed by the higher glycogen concentration (P<0.05) compared to the immediate post-exercise samples (15.4 vs. 7.9 ?g/mg wet wt); whereas, the LS horses did not return to normal levels until 24 h post SET. Results indicated that horses on the LS diet, which is representative of low-starch feeding programs commonly observed in the industry, replenish their skeletal muscle glycogen slower than horses on the HS diet. Based on this study, performance horses undergoing multiple bouts of intense exercise may benefit physiologically from receiving diets that contain more than 553.7 g of starch/day.