A Rapid Psychrometric Procedure for Water Activity Measurement of Foods in the Intermediate Moisture Range1

1981 ◽  
Vol 44 (12) ◽  
pp. 892-895 ◽  
Author(s):  
H. H. WIEBE ◽  
R. N. KIDAMBI ◽  
G. H. RICHARDSON ◽  
C. A. ERNSTROM
Keyword(s):  
Water Activity ◽  
Milk Powder ◽  
Standard Errors ◽  
Activity Measurement ◽  
Milk Chocolate ◽  
Step Procedure ◽  
Coefficients Of Variation ◽  
Sample Chamber ◽  
Juice Concentrate ◽  
Luncheon Meat

Commercial vapor pressure thermocouple psychrometers (hygrometers) are now generally accepted for measuring water activity, aw (water potential) in plants and soils, and commercial instruments are available. We have adapted them for aw measurements in the 0.99 to 0.60 range using a two-step procedure. Water is first condensed on the thermocouple; then the sample is inserted in the thermocouple chamber and the psychrometric cooling of the wet thermocouple measured. The procedure is calibrated with a series of saturated salt slurries of known aw values. Typical aw values (with standard deviations) for a variety of foods were: Cheddar cheese, 0.95 ± 0.03; Parmesan cheese, 0.76 ± 0.03; milk powder, 0.75 ± 0.02; milk chocolate, 0.60 ± 0.04; luncheon meat, 0.96 ± 0.03; bread, 0.95 ± 0.03; dried raisins, 0.82 ± 0.02; corn syrup, 0.60 ± 0.02; and orange juice concentrate, 0.80 ± 0.03. The coefficients of variation ranged from 1.9 to 5.8%. When compared with published values obtained by other methods, these figures were within the standard errors of measurement. The thermocouple detector did not foul since it had only vapor contact with the sample. An economical sample chamber and instrument is described. Analysis time is 4 to 8 min. The procedure is accurate, convenient and rapid.

scholarly journals Propiedades físicas de naranja agria cocristalizada: efecto del pH, sólidos solubles y zumo adicionado

2017 ◽  
Vol 28 (2) ◽  
pp. 427
Author(s):  
Ricardo David Andrade Pizarro ◽  
Kevin Blanquicett Gónzalez ◽  
Rafael Rangel terraza
Keyword(s):  
Water Activity ◽  
Orange Juice ◽  
Solid Material ◽  
Soluble Solids ◽  
High Humidity ◽  
High Solubility ◽  
Bitter Orange ◽  
Moisture Contents ◽  
Particulate Solid ◽  
Juice Concentrate

The aim of this study was to evaluate the conditions of co-crystallization of bitter orange juice with sucrose on the physicochemical properties of the product. Bitter orange juice was obtained with a mechanical juicer and concentrated on a rotary evaporator. Sucrose syrup 70 oBrix was subjected to heating and stirring of 1000 rpm, until a white color (118 °C) was observed. Bitter orange juice was added to the syrup, and the mixture was subjected to constant stirring of 600 rpm, to observe the formation of a particulate solid material. The co-crystals were dried, grinded and sieved. A dry co-crystal was determined: moisture, bulk density, solubility, water activity and repose angle. High proportion of bitter orange juice added (20%) and low content of soluble solids (50 °Brix) produced co-crystals with low moisture content (2.59%), water activity (0.52) and solubility time (69.4 s). High pH (4.5) of bitter orange juice concentrate produced co-crystals with low moisture contents (1.96%). The co-crystals of bitter orange juice showed good reconstitution characteristics (high solubility); however, these had high humidity (2.5 to 4.5%) and water activity (0.508 to 0.798). 

Mitotic Index of Invasive Breast Carcinoma

2009 ◽  
Vol 133 (11) ◽  
pp. 1826-1833 ◽  
Author(s):  
John S. Meyer ◽  
Eric Cosatto ◽  
Hans Peter Graf
Keyword(s):  
Breast Carcinoma ◽  
Mitotic Index ◽  
Clinical Decision Making ◽  
Clinical Decision ◽  
Mitotic Cell ◽  
Standard Errors ◽  
Mitotic Figure ◽  
Binomial Probability ◽  
Breast Carcinomas ◽  
Coefficients Of Variation

Abstract Context.—Mitotic figure counts are related to breast cancer behavior but have not been sufficiently reproducible to be accepted for clinical decision-making. Objective.—To improve reproducibility and accuracy of the mitotic count. Design.—Mitotic index (MI) was defined as the mitotic cell count per 10 high-power fields (HPFs), an area 0.183 mm2. Two to 6 replicate sets of 10 HPFs were counted from 328 invasive breast carcinomas. Standard errors and coefficients of variation for mean MI were compared with expected results predicted by the binomial distribution. Results.—The boundaries for MI that separated the data into equal thirds (tertials) were 1.14 and 5.33. Standard errors and coefficients of variation for MI followed distributions predicted by binomial probability. Mean coefficient of variation was 147% for the low tertial, 72% for the midtertial, and 34.6% for the upper tertial. Conclusions.—Standard errors for MI based on a single count of 10 HPFs are too broad and coefficients of variation too large to be acceptable for clinical use. This is explained as a binomial probability effect, possibly with a contribution from tumor heterogeneity. Errors can be reduced in proportion to the square root of the number of sets of 10 HPFs counted. Tertial cutoffs of MI of the Nottingham system currently used in breast carcinoma grading are too high to be applicable to the population we studied. We recommend validation of cutoffs before they are applied to a particular population of breast carcinomas. Counting 5 sets of 10 HPFs is necessary to accurately rank carcinomas with low MIs.

WATER ADSORPTION IN CEREAL FOODS AND WATER ACTIVITY MEASUREMENT

1980 ◽  
pp. 97-119 ◽  
Author(s):  
Jean-Louis Multon ◽  
Hervé Bizot ◽  
Bernadette Savet
Keyword(s):  
Water Activity ◽  
Water Adsorption ◽  
Activity Measurement

scholarly journals A Continuous Protein Methyltransferase (G9a) Assay for Enzyme Activity Measurement and Inhibitor Screening

2009 ◽  
Vol 14 (9) ◽  
pp. 1129-1133 ◽  
Author(s):  
Arunkumar Dhayalan ◽  
Emilia Dimitrova ◽  
Philipp Rathert ◽  
Albert Jeltsch
Keyword(s):  
Scintillation Counting ◽  
Standard Errors ◽  
Activity Measurement ◽  
Protein Methylation ◽  
Substrate Protein ◽  
Zinc Finger Motifs ◽  
Methylation Assay ◽  
Lysine Methyltransferase ◽  
Protein Methyltransferase ◽  
Nonhistone Substrate

The authors describe a continuous protein methylation assay using the G9a protein lysine methyltransferase and its substrate protein WIZ (widely interspaced zinc finger motifs). The assay is based on the coupling of the biotinylated substrate protein to streptavidin-coated FlashPlates and the transfer of radioactive methyl groups from the S-adenosyl-L-methionine to the substrate. The reaction progress is monitored continuously by proximity scintillation counting. The assay is very accurate, convenient, well suited for automation, and highly reproducible with standard errors in the range of 5%. Because of few pipetting steps and continuous data readout, it is ideal for high-throughput applications such as screening of inhibitors, testing many enzyme variants, or analyzing differences in methylation rates of different substrates under various conditions. By using this new assay, the IC 50 of AdoHcy and the G9a inhibitor BIX-01294 were determined for methylation of the G9a nonhistone substrate WIZ. ( Journal of Biomolecular Screening 2009:1129-1133)

Maillard reaction kinetics in milk powder: Effect of water activity at mild temperatures

2010 ◽  
Vol 20 (1) ◽  
pp. 40-45 ◽  
Author(s):  
A.S. Pereyra Gonzales ◽  
G.B. Naranjo ◽  
G.E. Leiva ◽  
L.S. Malec
Keyword(s):  
Reaction Kinetics ◽  
Water Activity ◽  
Maillard Reaction ◽  
Milk Powder ◽  
Effect Of Water

Effect of Osmotic Pre-treatment and Temperature Storage Conditions on Water Activity and Colour of Dried Apple

2018 ◽  
Vol 14 (2) ◽  
Author(s):  
Joanna Cichowska ◽  
Hanna Kowalska
Keyword(s):  
Water Activity ◽  
Freeze Drying ◽  
Sucrose Solution ◽  
Osmotic Dehydration ◽  
Storage Conditions ◽  
Juice Concentrate ◽  
Colour Changes ◽  
Higher Temperature ◽  
Pre Treatment ◽  
Chokeberry Juice

AbstractThe cylinders of apples cv.Braeburnwere subjected to osmotic dehydration in a sucrose solution with the addition of chokeberry juice concentrate. After osmotic pre-treatment the pieces of apples were dried by two methods: freeze-drying and air-drying. The storage results of dried apples at temperature 25–45 °C for 7 and 12 months were satisfactory. Mass changes were very minor. During storage dried apples obtained by both methods exhibited microbiological stability even after 7 and 12 months of storage, due to the fact that the water activity did not exceed the value of 0.4. Under the influence of the technological processes application, as well as storage conditions, appearance changes in the samples occurred. Higher temperature of storage had an increase impact in colour changes of control samples (without osmotic pre-treatment) and also osmotically dehydrated into sucrose solution, mainly in the case of samples which had dried using freeze-drying. Previously immersed in chokeberry juice concentrate, dried apples had colour changes comes from colour of solution.

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