The Loss of Added Lysine and Threonine During the Baking of Wheat Bread
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Rat growth experiments and microbiological assay methods were used to estimate the loss of added free L‐lysine·HCl and DL‐threonine during the baking of wheat bread. Introductory rat experiments showed that the optimum concentration for growth of L‐lysine. HCl added before baking was approximately 0.40‐0.45% of the fresh weight of the flour. The optimum concentrations of L‐lysine·HCl and DL‐threonine when added together were approximately 0.55% for the former amino acid and 0.30% for the latter. The loss of added L‐lysine·HCl during baking was found to be 10–15% as estimated by animal experiments and 5–10% as estimated by microbiological assays. The loss of L‐threonine (added as DL‐threonine) was significantly greater, amounting to approximately 40% as judged by the feeding trials and 20–25% according to the microbiological estimations. The amino acid compositions of the flour and the bread baked from the flour were also determined.Keywords:
Wheat bread
SUMMARY: Amino acid uptake by Methylococcus capsulatus was found to be effected by a transport system common to a wide range of amino acids. Some correlation existed between the amount of an amino acid incorporated and its effectiveness as a competitor against other amino acids, thus indicating different affinities among amino acids for the transport system. Uptake of some amino acids (e.g. the aromatic group and lysine) by an additional mechanism(s) is also suggested. Relief of threonine-inhibition of growth by metabolically related and unrelated amino acids is explained in terms of inhibition by other amino acids of the accumulation into the organisms of bacteriostatic levels of threonine. The threonine-resistant mutants isolated had decreased capacities to incorporate threonine and all the other amino acids tested.
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ABSTRACT Bread fortified with 0.48% L‐lysine (0.6% L‐lysine‐HCl) and 0.3% L‐threonine was baked at 210°C for 43 min and analyzed (lysine) calorimetrically and (threonine) microbiologically. Lysine and thre‐onine found in loaves were respectively compared with the values added to the dough. Baking loss of lysine and threonine was respectively 5 ± 6% and 3 ± 2% in the crumb and 46 ± 11% and 54 ± 8% in the crust. Loss of lysine was 14 ± 8% and of threonine 15 ± 5% in the whole loaf. However, the losses of these amino acids in the loaf could not be verified by the rat feeding test. The reason was discussed.
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Essential amino acid
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Abstract The response of adult rats fed diets containing amino acid mixtures with varying combinations of lysine and threonine was studied by estimating the change in body weights, organ weights, total nitrogen content of organs and the concentration of free plasma lysine and threonine. Analysis of variance indicates a significant effect of threonine, lysine and a significant interaction due to feeding the two amino acids on the body weights, organ weights and total nitrogen content of various organs. Significant effect on the level of the plasma free amino acid was also shown as a result of feeding the particular amino acid. Results show that in deficient animals the rates of building body protein are low but are higher in the lysine deficient animals than in the threonine deficient and protein deficient animals. The varying rates of exchanging protein between the various organs in response to changing the levels of amino acids in the diet would mean that total change in body protein or total nitrogen balance may not be satisfactory way to determine the protein or amino acid requirements for maintenance. It seems to be necessary to focus down on protein turnover rates in specific tissues.
Essential amino acid
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Dietary protein
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Over a 21-d experiment, the efficiency of lysine and threonine retention was determined in 80 male Sprague-Dawley rats (65.9 ± 0.3 g, means ± SE) fed purified diets containing an amino acid mix limiting in either lysine or threonine. With additional increments of the first limiting amino acid, lysine concentration in total body protein (g/16 g N) increased (P < 0.01) in rats fed lysine-limiting diets but, when fed threonine-limiting diets, lysine concentration in body protein first increased and then decreased (P < 0.01). As increments of the first limiting amino acid were added, the threonine concentration in total body protein increased then decreased when both lysine- (P < 0.01) and threonine- (P < 0.06) limiting diets were fed. Lysine and threonine retention were calculated based on comparative slaughter. Sixteen rats were killed on d 0 to estimate the grams of amino acid in the body. Retention responses were analyzed using a logistic equation in which lysine or threonine intake was used to predict retention. The maximum marginal efficiency (dr/dl, retention/intake) was observed at <40% of maximum retention. For lysine retention, it was 81% when lysine was limiting and 70% when threonine was limiting. For threonine retention, it was 58% when threonine was limiting and 49% when lysine was limiting. The maximum cumulative efficiency (retention adjusted for maintenance relative to cumulative intake) for lysine retention was 62% when lysine was limiting or 58% when threonine was limiting. For threonine retention, it was 51% when threonine was limiting and 35% when lysine was limiting. Thus, amino acid concentration in body protein is not constant, and amino acids are used with higher efficiency when first limiting.
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In adult fully grown rats deficient in L-Lysine, the speed of the irreversible degradation of free L-threonine equals 1.60 mmol/24 h/g as calculated for 1 mmol/kg administered. This speed is 23 per cent slower than that determined in non lysine deficient animals. This fact explains at least partially, the paradoxical resistance of the adult rat to the lysine deficiency.
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1. Experiments were conducted to establish the requirements and optimal dietary ratio of lysine to threonine for fast growing male chickens (genotype Ross 308) depending on age, daily protein deposition and of dietary amino acid efficiency. 2. A total of 216 growing chickens were utilised in nitrogen-balance studies in three age periods (10 to 25 d; 30 to 45 d; 50 to 65 d) using graded levels of protein supply (60 to 360 g/kg crude protein) in lysine or threonine limiting diets. 3. Supplementation of crystalline amino acids (L-Lys, L-Thr, DL-Met and L-Arg) provided the following amino acid ratios: lysine limiting diets (Lys:Met + Cys:Thr:Arg = 1 : 1.01 : 0.91 : 1.14), threonine limiting diets (Lys : Met + Cys : Thr : Arg = 1 : 0.85 : 0.54 : 1.16). 4. The principles of the diet dilution technique using an exponential function were applied for the modelling of lysine and threonine requirements. For equal daily protein deposition, optimal lysine to threonine ratios 1 : 0.69 (10 to 25 d), 1 : 0.70 (30 to 45 d) and 1 : 0.74 (50 to 65 d) were established. 5. For the commercial growth period of fast growing chickens, the derived optimal lysine to threonine ratio was constant (1 : 0.69). The applied modelling procedure gave conclusions for quantitative requirements and optimal dietary lysine:threonine ratios in line with actual recommendations.
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Alanine
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A total of 1800 pigs (Exp 1, 360; Exp. 2, 1440) were used in two experiments to evaluate the true ileal digestible (TID) lysine and threonine requirement for 24- to 44-lb pigs. In Exp. 1, there were eight pens per treatment, with five pigs (Genetiporc, initially 23.6 lb and 34 d of age) per pen. Experiment 1 was conducted as a combination of two separate trials to simultaneously examine both the TID lysine and threonine requirement, and hence, determine the appropriate threonine-to-lysine ratio. The first part of the trial consisted of five treatments formulated to contain 0.9, 1.0, 1.1, 1.2, or 1.3% TID lysine, with TID threonine at 66% of lysine. The second part consisted of five treatments formulated to 1.3% TID lysine with increasing TID threonine (0.60, 0.66, 0.73, 0.79, or 0.85%). Other amino acids were formulated to either meet or exceed requirement estimates, thereby ensuring lysine and threonine were first limiting. The highest concentrations of both lysine and threonine (1.3% and 0.85%, respectively) were combined in a single diet, which was used in both trials, to give a total of 10 treatments. From d 0 to 17, ADG and feed efficiency (F/G) improved as TID lysine (quadratic, P<0.02) and threonine (ADG, linear, P<0.03; F/G, quadratic, P<0.04) increased. Regression analysis showed that 95% or more of the maximum response was obtained at a TID threonine-to-lysine ratio of approximately 64% for ADG and 66% for F/G. In Exp. 2, there were 48 pigs per experimental unit (2 pens sharing a fenceline feeder) and six replications per treatment. Pigs (PIC, 24 lb and 39 d of age) were fed experimental diets containing 1.1% TID lysine (calculated to be less than their requirement estimate), with added Lthreonine to give TID threonine concentrations of 0.55, 0.60, 0.66, 0.72, or 0.77% and TID threonine-to-lysine ratios of 50, 55, 60, 65, and 70%. For the 21-d trial, ADG (quadratic, P<0.07) and F/G (quadratic, P<0.01) improved with increasing TID threonine. The best ADG and F/G were observed at 0.72% TID threonine. Hence, it seems that pigs weighing between 22 and 44 lb require approximately 0.72% TID threonine (0.81% total threonine) when fed 1.1% TID lysine, which corresponds to a TID threonine-tolysine ratio of 65%, similar to results in Exp. 1. Data from these two studies indicate an optimal TID threonine-to-lysine ratio of approximately 64 to 66% for 24- to 44-lb pigs.; Swine Day, 2004, Kansas State University, Manhattan, KS, 2004
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