SOLUTE MOBILITY IN RELATION TO WATER CONTENT AND WATER ACTIVITY

1981 ◽  
pp. 295-317 ◽  
Author(s):  
R.B. Duckworth
Keyword(s):  
Water Content ◽  
Water Activity

scholarly journals Penurunan mutu dan pendugaan umur simpan sup krim instan labu kuning diperkaya tempe untuk lansia dengan metode accelerated shelf life testing (ASLT)

2020 ◽  
Vol 8 (2) ◽  
pp. 134-142
Author(s):  
Salma Shafrina Aulia ◽  
Budi Setiawan ◽  
Tiurma Sinaga ◽  
Ahmad Sulaeman
Keyword(s):  
Lipid Oxidation ◽  
Shelf Life ◽  
Water Content ◽  
Water Activity ◽  
Critical Parameter ◽  
Storage Period ◽  
Life Testing ◽  
Quality Of Water ◽  
Long Time

Background: Instant pumpkin cream soup enriched with tempeh had fulfilled 10% Recommended Dietary Allowances (RDA) for elderly so that it can be used as an easy-to-serve snack, but decreasing quality of instant cream soup will be happened if the instant cream soup was stored for a long time. Objectives: This study aimed to analyze quality of water content, water activity and lipid oxidation in instant pumpkin cream soup during storage and estimated the shelf life of pumpkin cream soup enriched with tempeh.Method:  Quality storage was analyzed using of water content, water activity (aw) and lipid oxidation. Estimation of shelf life was analyzed using Arrhenius Accelerated Shelf Life Testing (ASLT) model.Results: The results showed that the water content, aw levels and lipid oxidation of instant pumpkin cream soup increased during the storage period. The critical parameter used in this study was lipid oxidation. Instant cream soup without the addition of tempeh can last 447 days  while the cream soup with the addition of tempeh has a shelf life of 433 days.Conclusion: Quality of instant pumpkin cream soup decreased during the storage period and it would be expired over a year.

Transient Water Transport in Nafion Membranes Under Activity Gradients

2010 ◽  
Author(s):  
T. Romero ◽  
W. Me´rida
Keyword(s):  
Water Content ◽  
Water Transport ◽  
Water Activity ◽  
Thickness Variation ◽  
Membrane Thickness ◽  
Membrane Interface ◽  
Rational Representation ◽  
Transport Measurements ◽  
Nafion Membranes ◽  
The Time Domain

Transient water transport experiments on Nafion of different thicknesses were carried out in the temperature range of 30 to 70 °C. These experiments report on water transport measurements under activity gradients in the time domain for liquid and vapour equilibrated Nafion membranes. Using a permeability test rig with a gated valve, the water crossover was measured as a function of time. The typical response is shown as a time dependent flux, and it shows the dynamic transport from an initially dry condition up to the final steady state. Contrarily to previous reports from dynamic water transport measurements, where the activity gradient across the membrane is absent; in this work, the membrane was subjected to an activity gradient acting as the driving force to transport water from an environment with higher water activity to an environment with lower water activity through the membrane’s structure. Measurements explored temperature and membrane thickness variation effect on the transient response. Results showed dependency on temperature and a slower water transport rate across the vapour-membrane interface than for the liquid-membrane interface. These measurements showed the transport dependency on water content at the beginning of the experiment when the membrane was in a close-to-dry condition suggesting a transport phenomenon transition due to a reached critical water content value. The new protocol for transient measurements proposed here will allow the characterization of water transport dependency on membrane water content with a more rational representation of the membrane-environment interface.

scholarly journals How NaCl and water content determine water activity during ripening of Gouda cheese, and the predicted effect on inhibition of Listeria monocytogenes

2016 ◽  
Vol 99 (7) ◽  
pp. 5192-5201 ◽  
Author(s):  
E. Wemmenhove ◽  
M.H.J. Wells-Bennik ◽  
A. Stara ◽  
A.C.M. van Hooijdonk ◽  
M.H. Zwietering
Keyword(s):  
Listeria Monocytogenes ◽  
Water Content ◽  
Water Activity ◽  
Gouda Cheese

scholarly journals Effects of Imprinting and Water Activity on Transesterification and Thermostability with Lipases in Ionic Liquid

2021 ◽  
Vol 35 (1) ◽  
pp. 57-63
Author(s):  
M. Matsumoto ◽  
K. Nakao ◽  
Y. Tahara
Keyword(s):  
Ionic Liquid ◽  
Water Content ◽  
Benzyl Alcohol ◽  
Vinyl Acetate ◽  
Water Activity ◽  
Maximum Rate ◽  
The Other ◽  
Organic Media ◽  
Catalytic Activities ◽  
Michaelis Constants

The effect of bio-imprinting and water activity on catalytic activities and the thermostability of lipases was investigated for transesterification using vinyl acetate and benzyl alcohol as substrates in ionic liquid, [Cnmim][PF6] (n=4,6,8), and benzene. The catalytic activities were enhanced by imprinting in benzene and [C4mim][PF6], and the relations between the transesterification activities and the water activity in both solvents were approximately bell shaped. The reactivity of the transesterification in benzene was higher than that in [C4<br /> mim][PF6]. The effects of water activity and imprinting on the kinetic parameters in [C4mim][PF6] were examined. Without controlling the water content, the values of Km,VA and Km,BA (Michaelis constants of vinyl acetate and benzyl alcohol, respectively) decreased, and the values of Vm (maximum rate) increased by imprinting. On the other hand, by controlling the water content in the organic media, the values of Vm, Km,VA, and Km,BA increased by imprinting. The activities of lipase in ionic liquid are more strongly affected by water activity and imprinting than those in benzene. We observed effects of water activity on thermostability but none from imprinting.

Fermentation Problem in Spanish North-Coast Honey

1995 ◽  
Vol 58 (5) ◽  
pp. 515-518 ◽  
Author(s):  
SUSANA SANZ ◽  
GLORIA GRADILLAS ◽  
FUENCISLA JIMENO ◽  
CONSUELO PEREZ ◽  
TERESA JUAN
Keyword(s):  
Water Content ◽  
Water Activity ◽  
Microbiological Quality ◽  
Free Water ◽  
High Water ◽  
North Coast ◽  
High Water Content ◽  
Free Water Content ◽  
Cantabrian Coast ◽  
Mold And Yeast

Twenty-one samples from the Cantabrian coast were analyzed to establish their microbiological quality and fermentation tendency. In a food with a very low free-water content like honey, microbiological growth is only possible when there is an increase in water activity. Since most of the samples studied were not extensively granulated, the risk of fermentation is mostly due to high water content. Among our samples, only two had a water content below 17.1% (no risk of fermentation), whereas the high water activity of the rest of the samples indicates the possibility of microbial growth. In fact, four of the samples analyzed showed a moisture content over the Spanish maximum legal limit, which means a high risk of fermentation. The absence of Enterobacteriaceae, coliforms, and Escherichia coli in our samples indicates an appropriate cleanliness during extractions and handling of honey. No Salmonella or Shigella were found. The relationship between water activity and mold and yeast counts found for the honeys analyzed allowed us to divide our samples in two groups: honeys with a high or a low risk of fermentation. Changes observed during storage of the samples confirmed this classification.

scholarly journals Isotherms and isostatic heat of foam-mat dried yellow mombin pulp

2018 ◽  
Vol 22 (6) ◽  
pp. 436-441
Author(s):  
Maisa D. Cavalcante ◽  
Geovana R. Plácido ◽  
Daniel E. C. de Oliveira ◽  
Bheatriz S. M. de Freitas ◽  
Caroline Cagnin ◽  
...  
Keyword(s):  
Water Content ◽  
Water Activity ◽  
Nutritional Value ◽  
Isosteric Heat ◽  
Agricultural Products ◽  
Equilibrium Water Content ◽  
Desorption Isotherms ◽  
Forced Air ◽  
Semi Solid ◽  
Content Range

ABSTRACT Yellow mombin has high nutritional value but is very perishable. Foam mat drying is a method that has been widely used to preserve liquid and semi-solid powdered foods. In this context, the aim of this study was to determine desorption isotherms and isosteric heat of yellow mombin (Spondias mombin L.) foam for different conditions of temperature and water activity. Powdered yellow mombin pulp was obtained by drying in forced-air oven regulated to 60 ° C. The indirect static method was used to determine the isotherms and isosteric heat, whereas water activity (aw) was determined using the Hygropalm-HP23AW-A analyzer. A B.O.D. incubator, set at 10, 20, 30 and 40 °C, was used to control the temperature, and the water activity for each temperature was between 0.220 and 0.832. The experimental data were fitted to mathematical models frequently used to represent the hygroscopicity of agricultural products, and the best model was the Modified Halsey. Integral isosteric heat of desorption of yellow mombin powder, within the water content range of 17.22 to 57.58 (% d.b.), ranged from 3198.56 to 2598.38 kJ kg-1. It was concluded that the equilibrium water content of yellow mombin pulp powder increased with the increment in water activity; desorption isotherms obtained for yellow mombin pulp powder showed sigmoid form and, with the reduction of water content, the isosteric heat increases.

scholarly journals Physico-chemical indicators and identification of selected Slovak honeys based on colour measurement

2012 ◽  
Vol 81 (1) ◽  
pp. 57-61 ◽  
Author(s):  
Jana Kasperová ◽  
Jozef Nagy ◽  
Peter Popelka ◽  
Zuzana Dičáková ◽  
Alena Nagyová ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Chemical Analysis ◽  
Water Content ◽  
Water Activity ◽  
Colour Measurement ◽  
Free Acidity ◽  
Mean Values ◽  
Chemical Indicators ◽  
Council Directive ◽  
Physico Chemical

The aim of study was to characterize 52 samples of Slovak honeys of six types (multifloral, acacia, rape, honeydew, forest and mixed). Physico-chemical analysis of honey included the water content, free acidity, pH, water activity, electrical conductivity, and hydroxymethylfurfural (HMF) content. In addition, the colour of honeys was measured using spectrophotometer and Commission Internationale de I`Eclairage method (CIE L*a*b*); four types of honey were used for identification: multifloral, acacia, rape, and honeydew. Mean values of physico-chemical indicators were as follows: water content 16–21%, acidity 6–42 mekv·kg-1, pH 3.68–5.15, water activity 0.505–0.667, electrical conductivity 0.155–1.585 mS·cm-1 and HMF content 0.17–78.5 mg·kg-1. The highest HMF content was found in forest honey with one sample above the limit established by Council Directive 2001/110/EC. The colour of Slovak honeys analysed in this study was very variable and ranged from pale yellow to dark brown. Differences of physico-chemical indicators and colour of honey samples were found to be significant (P < 0.05). The CIE L*a*b* methods can be used for identification of selected honey samples. This is the first similar study on Slovak honey.

scholarly journals Stability of cactus-pear powder during storage

2016 ◽  
Vol 20 (2) ◽  
pp. 169-173
Author(s):  
Plúvia O. Galdino ◽  
Rossana M. F. de Figueirêdo ◽  
Alexandre J. de M. Queiroz ◽  
Pablícia O. Galdino ◽  
Tâmila K. da S. Fernandes
Keyword(s):  
Water Content ◽  
Water Activity ◽  
Reducing Sugars ◽  
Titratable Acidity ◽  
High Water ◽  
Soluble Solids ◽  
High Water Content ◽  
Cactus Pear ◽  
Total Titratable Acidity ◽  
The Stability

ABSTRACT The stability of cactus-pear powder, obtained by the process of spray drying for 40 days, was evaluated under controlled conditions of relative air humidity (83%) and temperature (25 and 40 °C). The whole pulp was characterized with regard to its physico-chemical parameters: pH, total titratable acidity, soluble solids, water content, total solids, ashes, reducing sugars, total sugars, non-reducing sugars, luminosity, redness, yellowness and water activity. The stored samples in powder were evaluated every 10 days for water content, water activity, total titratable acidity and color (luminosity, redness and yellowness). The whole pulp was slightly acidic and perishable, due to the high water content. During storage, the packages did not prevent water absorption, thus increasing water content and, consequently, water activity. Yellowness oscillated along the storage time, but the predominance of the yellow color was not affected.

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