scholarly journals Stability of tryptophan during food processing and storage

1985 ◽  
Vol 53 (2) ◽  
pp. 293-300 ◽  
Author(s):  
Henrik K. Nielsen ◽  
A. Klein ◽  
R. F. Hurrell
Keyword(s):  
Alkaline Hydrolysis ◽  
Food Processing ◽  
Model Systems ◽  
Chemical Methods ◽  
Processing And Storage ◽  
And Storage ◽  
Hplc Measurement ◽  
Colorimetric Reaction ◽  
Good Agreement

1. Tryptophan losses in stored milk powders and in different model systems representing the major reactions of food proteins during processing and storage were determined using four different chemical methods and in a rat assay.2. Similar tryptophan values were obtained by the three chemical methods which included high pressure liquid chromatography (HPLC) after sodium hydroxide hydrolysis. colorimetric reaction withp-dimethylamino- benzaldehyde (p-DAB) after barium hydroxide hydrolysis, and fluorescence of the Norharman derivative after NaOH hydrolysis.3. Tryptophan losses in the treated proteins as measured by the alkaline-hydrolysis methods were generally smaller than those determined by the rat assay. Good agreement however was obtained when the chemical value was multiplied by the true nitrogen digestibility.4. Determination of tryptophan by reaction withp-DAB after papain (EC 3.4.22.2) digestion gave lower values in the processed proteins than the other chemical methods or the rat assay.5. A method using alkaline-hydrolysis is recommended, preferably combined with HPLC-measurement of the liberated tryptophan.

scholarly journals Stability of tryptophan during food processing and storage

1985 ◽  
Vol 53 (2) ◽  
pp. 281-292 ◽  
Author(s):  
Henrik K. Nielsen ◽  
D. De Weck ◽  
P. A. Finot ◽  
R. Liardon ◽  
R. F. Hurrell
Keyword(s):  
Food Processing ◽  
Whey Proteins ◽  
Milk Powder ◽  
Protein Digestibility ◽  
Model Systems ◽  
Maillard Reactions ◽  
Minor Losses ◽  
Oxidation Of Methionine ◽  
Processing And Storage ◽  
And Storage

1. The stability of tryptophan was evaluated in several different food model systems using a chemical method (high pressure liquid chromatography after alkaline-hydrolysis) and rat assays. Losses of tryptophan were compared with the losses of lysine and methionine.2. Whey proteins stored in the presence of oxidizing lipids showed large losses of lysine and extensive methionine oxidation but only minor losses of tryptophan as measured chemically. The observed decrease in bioavailable tryptophan was explained by a lower protein digestibility.3. Casein treated with hydrogen peroxide to oxidize all methionine to methionine sulphoxide showed a 9% loss in bioavailable tryptophan.4. When casein was reacted with caffeic acid at pH 7 in the presence of monophenol monooxygenase (tyrosinase; EC 1.14.18.l), no chemical loss of tryptophan occurred, although fluorodinitrobenzene-reactive lysine fell by 23%. Tryptophan bioavailability fell IS%, partly due to an 8% reduction in protein digestibility.5. Alkali-treated casein (0.15 M-sodium hydroxide, 80°,4 h) did not support rat growth. Chemically-determined tryptophan, available tryptophan and true nitrogen digestibility fell 10, 46 and 23% respectively. Racemization of tryptophan was found to be 10% (D/(D+L)).6. In whole-milk powder, which had undergone ‘early’ or ‘advanced’ Maillard reactions, tryptophan, determined chemically or in rat assays, was virtually unchanged. Extensive lysine losses occurred.7. It was concluded that losses of tryptophan during food processing and storage are small and of only minor nutritional importance, especially when compared with much larger losses of lysine and the more extensive oxidation of methionine.

scholarly journals Determination of the Chemical Composition of Tea by Chromatographic Methods: A Review

2015 ◽  
Vol 4 (3) ◽  
pp. 56 ◽  
Author(s):  
Alexandr Ya Yashin ◽  
Boris V. Nemzer ◽  
Emilie Combet ◽  
Yakov I. Yashin
Keyword(s):  
Chemical Composition ◽  
Volatile Compounds ◽  
Black Tea ◽  
Storage Conditions ◽  
Organoleptic Evaluation ◽  
Chromatographic Methods ◽  
Tea Quality ◽  
Processing And Storage ◽  
And Storage

<p>Despite the fact that mankind has been drinking tea for more than 5000 years, its chemical composition has been studied only in recent decades. These studies are primarily carried out using chromatographic methods. This review summarizes the latest information regarding the chemical composition of different tea grades by different chromatographic methods, which has not previously been reviewed in the same scope. Over the last 40 years, the qualitative and quantitative analyses of high volatile compounds were determined by GC and GC/MS. The main components responsible for aroma of green and black tea were revealed, and the low volatile compounds basically were determined by HPLC and LC/MS methods. Most studies focusing on the determination of catechins and caffeine in various teas (green, oolong, black and pu-erh) involved HPLC analysis.</p> <p>Knowledge of tea chemical composition helps in assessing its quality on the one hand, and helps to monitor and manage its growing, processing, and storage conditions on the other. In particular, this knowledge has enabled to establish the relationships between the chemical composition of tea and its properties by identifying the tea constituents which determine its aroma and taste. Therefore, assessment of tea quality does not only rely on subjective organoleptic evaluation, but also on objective physical and chemical methods, with extra determination of tea components most beneficial to human health. With this knowledge, the nutritional value of tea may be increased, and tea quality improved by providing via optimization of the growing, processing, and storage conditions.</p>

Stability of Lycopene During Food Processing and Storage

2005 ◽  
Vol 8 (4) ◽  
pp. 413-422 ◽  
Author(s):  
S. Xianquan ◽  
J. Shi ◽  
Y. Kakuda ◽  
J. Yueming
Keyword(s):  
Food Processing ◽  
Processing And Storage ◽  
And Storage

scholarly journals Post-harvest content of free titratable acids in the grain of proso millet varieties (Panicum milliaceum L.), and changes during grain processing and storage

2010 ◽  
Vol 46 (Special Issue) ◽  
pp. S90-S95 ◽  
Author(s):  
V. Dvořáček ◽  
D. Janovská ◽  
L. Papoušková ◽  
E. Bicanová
Keyword(s):  
Dry Matter ◽  
Slight Modification ◽  
Storage Conditions ◽  
Panicum Miliaceum ◽  
Proso Millet ◽  
Grain Processing ◽  
Sensory Changes ◽  
Processing And Storage ◽  
And Storage

A triennial evaluation of the content of titratable acids (TA) in grain was carried out on 12 varieties of proso millet (<I>Panicum miliaceum </I>L.). The model variety, Mironovskoe 94, harvested in 2004, was used for the monitoring of sensory changes in TA content, in relationship to different storage conditions and the application of different grain processing methods. The Czech state norm (CSN 56 0512-9 1995) Determination of Titratable Acids, with a slight modification, was used as the standard method. The TA contents in dry matter varied between 39 and 78 mmol/kg of grain dry matter, and significant differences between varieties and experimental years were found. The method of proso millet processing had a key role in the final sensitivity to rancidity. The storage conditions had a much lower influence on TA content than the processing technology. The clearly detected sensory changes found in scoured grains corresponded with TA contents within the range of 90 to106 mmol/kg. The monitoring of the TA content can be considered as a suitable tool for the prediction of rancidity processes in millet grains.

The Automated Determination of Serum Uric Acid

1966 ◽  
Vol 12 (11) ◽  
pp. 748-766 ◽  
Author(s):  
Stanley Morgenstern ◽  
Richard V Flor ◽  
James H Kaufman ◽  
Bernard Klein
Keyword(s):  
Uric Acid ◽  
Serum Uric Acid ◽  
Enzymatic Reaction ◽  
Enzymatic Determination ◽  
Before And After ◽  
The Difference ◽  
Automated Determination ◽  
Colorimetric Reaction ◽  
Good Agreement

Abstract An automated procedure is presented for the enzymatic determination of serum uric acid on both the AutoAnalyzer and the Robot Chemist. The procedure measures as the neocuproine complex, the difference in the amount of Cu+ formed by reaction of a Cu++-alkanolamine buffered solution with serum uric acid under precisely controlled conditions before and after uricase treatment of the serum. The difference is proportional to the true serum uric acid content. The elements contributing to the enzymatic reaction, the colorimetric reaction, and the elimination of interferences were investigated. Comparison of serum uric acid values obtained by this method with those obtained by ultraviolet spectrophotometry show very good agreement.

scholarly journals Functionality changes of natural antioxidants during food processing and storage

2004 ◽  
Vol 22 (SI - Chem. Reactions in Foods V) ◽  
pp. S80-S83 ◽  
Author(s):  
J. Pokorný ◽  
Š. Schmidt ◽  
H. T T Nguyen
Keyword(s):  
Antioxidant Activity ◽  
Free Radicals ◽  
Food Processing ◽  
Degradation Products ◽  
Raw Materials ◽  
Natural Antioxidants ◽  
Phenolic Antioxidants ◽  
Oxidation Reactions ◽  
Processing And Storage ◽  
And Storage

Food raw materials and products contain inhibitors of oxidation reactions, both in the lipidic phase and the aqueous phase. The most important inhibitors are phenolic antioxidants. During food processing and storage, concentrations of antioxidants in the two phases reach an equilibrium. Phenolics react with lipidic free radicals, being converted into antioxidant free radicals, quinones, polymers and copolymers. Some degradation products possess an antioxidant activity, too. The relative antioxidant activity decreases with decreasing concentration of oxygen in the system and with increasing temperature. Antioxidants are more rapidly decomposed in surface layers. Health aspects of antioxidant degradation products are often neglected as the safety of antioxidant degradation products is mostly unknown.

scholarly journals Application of image analysis for determination of rapeseed dimensions using IoT concept

2020 ◽  
Vol 45 (3) ◽  
pp. 44-52
Author(s):  
Dušan Marković ◽  
Ranko Koprivica ◽  
Biljana Veljković ◽  
Dejan Vujičić ◽  
Uroš Pešović ◽  
...  
Keyword(s):  
Image Analysis ◽  
The Internet ◽  
Equivalent Diameter ◽  
Slow Process ◽  
Cross Sectional ◽  
First Results ◽  
Processing And Storage ◽  
And Storage ◽  
The Internet Of Things

The paper analyzes the geometric characteristics of seeds, uniformity and cross - sectional area of rapeseed, on the basis of which the equivalent diameter was calculated. Knowing the dimensions of seeds is important in seed production from sowing, harvesting, processing, and storage, to seed packaging. Manual determination of the dimensions of seeds is a rather slow process, so the aim of this work was to show a computer-aided device that contains a camera and can take seed samples, while determining the dimensions of seeds by program image analysis. Presented device is realized in accordance with the concept of the Internet of Things (IoT) so it has the ability to connect to the Internet and forward the image, or in another variant can directly perform the image analysis and further forward the results only. The purpose of the presented system for determining the size of seeds is providing a fast and efficient way for users to get the first results that will help them in the implementation of further activities related to working with small seeds.

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