550. Colour changes in heated and unheated milk: I. The browning of milk on heating

1954 ◽  
Vol 21 (2) ◽  
pp. 194-203 ◽  
Author(s):  
H. Burton
Keyword(s):  
Visible Spectrum ◽  
Colour Changes

Methods for measuring the reflectance of milk are described. The effect of heating is to reduce the reflectance of whole and separated milk progressively towards the blue end of the visible spectrum. The reflectance of cream is almost unaffected. The measurement of reflectance at the blue end of the visible spectrum is shown to be a useful method for the determination of the brownness of milk. The variation of rate of browning with temperature and with pH and the effect of storage on brownness are given.

TLC Determination of Aquatic Humic Acids

1992 ◽  
Vol 26 (9-11) ◽  
pp. 2567-2570 ◽  
Author(s):  
M. Kaštelan-Macan ◽  
Š. Cerjan-Stefanovic ◽  
D. Jalšovec
Keyword(s):  
Thin Layer ◽  
Quantitative Determination ◽  
Humic Acids ◽  
Visible Spectrum ◽  
Solvent System ◽  
Spectroscopic Methods ◽  
Precise Method ◽  
Adsorption Resin ◽  
Layer Chromatography

Humic acids are mostly determined by spectroscopic methods, although they are not accurate enough, because humic acids possess no maximum absorption at any wavelength in the ultraviolet and visible spectrum. In this contribution the accurate and precise method for aquatic humic acids determination, using thin layer chromatography, was worked out. Previously, humic acids were separated and preconcentrated -from the river water, using macroreticular adsorption resin Amberlite XAD-4, and subsequently determined by TLC. The Chromatographie system was: silicagel HF254(Merck, precoated plates 20 × 20 cm) and NH3 -acetone (60:40,v/v) as a solvent system. Quantitative determination was made by Camag– Turner 111 Fluorimeter, by measuring UV–quenching.

scholarly journals The Influence of 30 Years Outdoor Weathering on the Durability of Hydrophobic Agents Applied on Obernkirchener Sandstones

Buildings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 18 ◽  
Author(s):  
Jeanette Orlowsky ◽  
Franziska Braun ◽  
Melanie Groh
Keyword(s):  
Water Absorption ◽  
Water Uptake ◽  
Capillary Water ◽  
Capillary Water Absorption ◽  
Absorption Determination ◽  
Colour Changes ◽  
Uptake Velocity ◽  
Outdoor Weathering

The durability of eleven different water repellents applied on one sandstone type was studied after a long-term weathering at seven different locations in Germany. By measuring colour changes, it could be shown that the formation of black crusts, the deposition of particles and biogenic growth caused a gradual darkening as well as significant changes in total colour over time. Additionally, the water absorption behaviour was investigated with two different methods: applying a low pressure using the pipe method and capillary water absorption measurements from a wet underlay. Afterwards, the test results were analysed with four different evaluation methods: calculation of the protection degree from pipe method and capillary water absorption, determination of the velocity of water uptake during capillary water absorption and calculation of the damaged depth of the stone surface using single-sided NMR technique. The growing damaged depth leads to an increase of the water uptake velocity and to a decrease of the protection degree of the applied hydrophobing agents. Three protective agents based on isobutyltrimethoxysilane showed already after two years of outdoor weathering a clear loss of performance, which significantly increased after 30 years of exposure.

Spectrophotometric Determination of Aminacrine Hydrochloride in Creams, Jellies, and Suppositories: Interlaboratory Study

1987 ◽  
Vol 70 (3) ◽  
pp. 560-565
Author(s):  
Elaine A Bunch
Keyword(s):  
Thin Layer ◽  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Coefficient Of Variation ◽  
Visible Spectrum ◽  
Interlaboratory Study ◽  
Commercial Products ◽  
Absorbance Maximum

Abstract A previously reported visible spectrophotometric method for the analysis of aminacrine hydrochloride in creams, jellies, and suppositories was studied collaboratively by 8 laboratories. Aminacrine hydrochloride was extracted into acidic ethanol and its visible spectrum recorded. The amount present was calculated by determining the net absorbance between the absorbance maximum at about 402 nm and one-half the sum of the absorbance of the minima at about 389 and 412 nm. Each collaborator received 4 creams (0.2%), 1 jel (0.2%), 1 molded suppository (6 mg/3.198 g), and 2 gelatin-encapsulated suppository samples (12 mg/6.661 g and 14 mg/6.863 g). The cream samples included blind duplicates prepared to contain 0.212% aminacrine hydrochloride, 15% sulfanilamide, and 2% allantoin. Mean recovery for the authentic cream was 104.7% with a coefficient of variation (CV) of 9.22%. The commercial products contained these respective amounts (CVs): creams, 100.0% (2.48%) and 101.5% (2.16%); jel, 118.0% (9.58%); molded suppository, 102.7% (1.88%); and gelatin encapsulated suppositories, 93.1% (1.0%) and 94.3% (1.60%). Standard aminacrine hydrochloride provided for the study was 99.6% pure by nonaqueous titration. Thin layer chromatographic identification of aminacrine hydrochloride was also tested collaboratively. The method was not adopted by AOAC.

615. Colour changes in heated and unheated milk V. The effects of temperature of measurement, pH, and the addition of certain ions on the reflectance of separated milk

1956 ◽  
Vol 23 (1) ◽  
pp. 92-104 ◽  
Author(s):  
H. Burton
Keyword(s):  
Wave Length ◽  
Bound Water ◽  
Visible Spectrum ◽  
Ion Distribution ◽  
Phosphate Ions ◽  
Liquid Phases ◽  
Colour Changes ◽  
Reflectance Change ◽  
Effects Of Temperature ◽  
Bound Water Content

Variation in the temperature of measurement, pH, and concentration of calcium, citrate and phosphate ions have been consistently found to affect the reflectance of separated milk in such a way that the entire curve of reflectance versus wave-length in the visible spectrum is raised or lowered. At temperatures between 10 and 50°C. the reflectance rises reversibly with temperature. The change is not instantaneous, and if the temperature is changed abruptly the reflectance change to the new value is exponential, with a time constant of about 40 min.Reflectance is independent of pH in the range 5·8–6·6, but for greater values it drops sharply.Added calcium ions increase the reflectance of separated milk, and added citrate and phosphate ions decrease it, independently of the simultaneous changes in pH.It is suggested that the reflectance changes which have been found to occur are all caused by changes in the sizes of the casein particles in milk which are brought about by the factors considered. The results given by other authors on viscosity and bound water content, and on direct electron-micrographic observation of casein, are cited to support this contention.It is further suggested that the change in casein particle size with temperature may be due to a change in the calcium-ion distribution between solid and liquid phases.The viscosity and reflectance results for separated milk heated to 70°C. and above are apparently anomalous, but they can be explained on the hypothesis that denatured soluble proteins aggregate into particles having a high ration of length to breadth.

scholarly journals The Efficacy of Polymer Coatings for the Protection of Electroless Copper Plated Polyester Fabric

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1277 ◽  
Author(s):  
Alenka Ojstršek ◽  
Natalija Virant ◽  
Daryl Fox ◽  
Latha Krishnan ◽  
Andrew Cobley
Keyword(s):  
Screen Printing ◽  
Base Material ◽  
Polyester Fabric ◽  
Polymer Coatings ◽  
Mechanical Characterisation ◽  
Polyurethane Resin ◽  
Colour Changes ◽  
Acrylate Resin ◽  
Photo Stability

The selective metallisation of textiles is becoming a very important process in the development of electronic or e-textiles. This study investigated the efficacy of polymer coatings for the protection of copper (Cu) conductive tracks electroless plated on polyester (PES) fabric against laundering and rubbing, without essentially affecting the physical-mechanical and optical properties of the base material. After the electroless deposition of a consistent layer of Cu onto PES, four polymers were applied individually by screen-printing or padding. The physical-mechanical characterisation of coated textiles revealed that polyurethane resin (PUR) and modified acrylate resin (AR) had little effect on the air permeability, tensile strength and breaking tenacity of the PES, as compared to silicone elastomer polydimethylsiloxane (PDMS) and epoxy resin (ER). On the other hand, PUR and PDMS had higher abrasion resistance and photo-stability under prolonged UV irradiation, as compared to AR and ER. In addition, freshly Cu plated samples were coated with polymers, washed up to 30 cycles and characterised by measuring their electrical resistivity, determination of colour changes and the examination of the surface morphology. Based on these results, PUR presented the most suitable protection of Cu tracks on PES, with the lowest impact on physical-mechanical properties. ER is not recommended to be used for protection of Cu tracks on fabrics, due to its rigidity, low photo-stability, washing and wear durability.

Electroretinographic Determination of Spectral Sensitivity in Albino and Pigmented Brook Trout (Salvelinus fontinalis, Mitchill)

1971 ◽  
Vol 49 (12) ◽  
pp. 1030-1037 ◽  
Author(s):  
H. Kobayashi ◽  
M. A. Ali
Keyword(s):  
Absorption Spectrum ◽  
Spectral Sensitivity ◽  
Brook Trout ◽  
Salvelinus Fontinalis ◽  
Narrow Band ◽  
Visible Spectrum ◽  
The Difference

A technique for recording electroretinograms from the unpunctured eyes in situ of living, anesthetized fish is described. This technique permits the use of the same fish in a number of experiments over a period of weeks, months, or years. Using this technique the spectral sensitivity of dark-adapted (scotopic) and light-adapted (photopic) fish was measured at 13 bands of the visible spectrum. The scotopic curves of albino and pigmented trout thus obtained in the winter have their maxima around 525 nm which differ from that of the absorption spectrum of the scotopic pigment in situ and in vitro of older fish obtained in the summer. The photopic curve of the pigmented fish is a broad one with humps around 425 nm, 545 nm, and 595 nm. The albino's curve has a relatively narrow band with a peak around 630 nm and a shoulder at about 550 nm. The difference between the shapes of the two curves may be ascribed to the increase in the intensity of light of longer wavelengths within the eyeball of the albino, due to reflection from blood vessels and sclera caused by the absence of pigmentation.

A SPECTROPHOTOMETRIC DETERMINATION OF EXHAUST GAS TEMPERATURES IN THE PULSE-JET ENGINE

1950 ◽  
Vol 28a (4) ◽  
pp. 411-432
Author(s):  
H. F. Quinn
Keyword(s):  
Present Method ◽  
Flame Temperature ◽  
Visible Spectrum ◽  
Black Body ◽  
Small Region ◽  
Black Body Radiation ◽  
Appreciable Amount ◽  
Jet Engine ◽  
Pulse Jet

This paper describes a spectrophotometric method whereby instantaneous values of a variable flame temperature, in the particular case of nonluminous flames, may be determined and continuously recorded.This new technique, which depends upon the establishment of monochromatic black-body radiation conditions in the flame for a small region in the visible spectrum, involves the continuous measurement of radiation intensity in the above region, the intensity being, thereafter, correlated with the temperature of the flame.The problem of temperature measurement in the general case of nonluminous flames (flames which do not contain an appreciable amount of free carbon in the form of soot) is considered and a brief review of previous techniques employed for this purpose over the past 50 years is given. The basic theory and preliminary experimental justification of the present method are discussed.A description of the apparatus and the experimental arrangement used by the author in a specific application of the present method in the determination of the time variation of temperature in the exhaust flame of a pulse-jet engine is given. This includes details of a special type of spectrophotometer which employs a multiplier photocell as the radiation detecting and measuring element and, also, a "black-body" cavity constructed as a standard radiation source for the calibration of the former instrument. An original technique used to investigate the emissivity of flames colored by alkali metal vapors is described and its application to the present problem shown.Finally, the measurable temperature range of the present apparatus is considered together with the inherent limitations of the new method.

Online determination of coffee roast degree toward controlling acidity

2020 ◽  
Vol 28 (4) ◽  
pp. 175-185
Author(s):  
Nathan Yergenson ◽  
D Eric Aston
Keyword(s):  
Near Infrared ◽  
Color Space ◽  
Visible Spectrum ◽  
Titratable Acidity ◽  
Least Squares Regression ◽  
L Value ◽  
Linear Effects ◽  
The Common ◽  
Roasting Temperature

Three methods of measuring coffee roast degree were compared using titratable acidity as an indicator of roast-dependent flavor change. The first roast degree method was based on prediction of the cracks with online near infrared spectroscopy and partial least squares regression, the second was based on changes in online near infrared absorbance, and the third was the common L* value from the CIELAB color space in the visible spectrum. Roasting trials utilized arabica coffee from eight origins in an air roaster, and results demonstrated the superiority of an online near infrared sensor for real-time roast degree measurement. A second dataset with constant temperature roasts showed how acidity can be controlled by changing both the roasting temperature and roast degree, finding the linear effects of roast time and roast degree on acidity.

Sign in / Sign up

Export Citation Format

Share Document