Inverse problem methodology for thermal-physical properties estimation of frozen green beans

Frozen green beans (Phaseolus vulgaris, L.) thermal conductivity (k) and heat capacity (Cp) were determined experimentally by a one dimensional finite difference (transient method) and differential scanning calorimetry, respectively. Thermal properties were also estimated by the inverse problem methodology (IPM). Heat capacity and thermal conductivity behaviour with temperature were modelled by the Schwartzberg equations and linear relationship, respectively below and above the melting point. These equations were used inside a finite element model (FEM) to simulate green beans phase transition under thawing conditions. The sequential simplex method was used to minimise the error vector of the FEM inverse problem, to estimate thermal capacity and thermal conductivity. The accuracy of thermal-physical properties estimated by the two methodologies was compared with data from literature. The thermo-physical properties estimated by the IPM converged for physically meaningful values. Important conclusions were obtained about errors in model predictions. Furthermore, the IPM thermal properties increased the accuracy of simulations, especially during phase transition

Haricots verts congelés : modélisation de la diminution de l’intensité de la couleur et de la teneur en chlorophylle

Colour changes and chlorophyll degradation of frozen green beans (Phaseolus vulgaris, L., variety bencanta) were studied during 250 days of storage at 7, 15 and 30 C. Chlorophyll a and b losses and colour Hunter a and b coordinates and total colour difference (TCDH) changes were successfully described by first order and reversible first order models, respectively. The temperature effect was described by the Arrhenius law. Disagreement between the colour co-ordinates and chlorophyll content was obtained. Therefore, chlorophyll content is not a good colour index of frozen green beans. The results emphasise that colour is a more important parameter to assess frozen green beans visual quality. # 2002 Elsevier Science Ltd and IIR. All rights reserved

Green beans (Phaseolus vulgaris, L.) quality loss upon thawing

Frozen green beans (Phaseolus vulgaris, L.) thawing is one of the operations that compromises significantly quality. The present research aims at studying the effects of thawing, at environmental and refrigeration temperatures, on the quality profile of a frozen green beans package. Quality losses were computationally evaluated, using a simulation system based on object-oriented technologies. Simulations show that sensory parameters, such as flavour and colour, are more sensitive to thawing at environmental temperatures, than nutritional parameters, such as vitamin C and starch contents. The study demonstrates that green beans quality retention is also influenced by packaging materials, with different degrees of thermal insulation, and environmental conditions, such as temperature and surface heat convection coefficients. Important conclusions are discussed on shelf-life limiting quality parameters during thawing and temperature abuses, as well as on thawing green vegetables to maximise their quality profile. Results emphasise that the principle of high-temperature–short-times is not directly applicable to frozen green beans thawing. Furthermore, simulations lead to the conclusion that overall quality profile is maximised by thawing under refrigeration temperatures

The effect of home storage conditions and packaging materials on the quality of frozen green beans

Home storage is the final step of the frozen foods distribution chain, and little is known on how it affects the products quality. The present research describes frozen green beans (Phaseolus vulgaris, L.) quality retention profile during the recommended ‘star marking’ system dates, at the storage temperatures of þ5,26, 212 and 218 8C (along 1, 4, 14 and 60 days, respectively). The quality profile was assessed by a simulation system. Simulations were set by a response surface methodology to access the effect of different packaging materials (thermal conductivities and thickness), surface heat transfer coefficient, and refrigerator dynamics (effect of refrigeration cycles at the different storage temperatures) on the average retentions of Ascorbic Acid, total vitamin C, colour and flavour. Green beans quality losses along frozen storage are significantly influenced by temperature, refrigerator dynamics and kinetic properties. Quality is also highly dependent on packaging materials thermal insulation (e.g. at temperatures above the melting point). Temperature cycles inside frozen chambers have a long term effect, and at the higher storage temperatures (e.g. T . 26 8C) are detrimental to frozen green beans quality after shorter periods

Novel pharmacological actions of Trequinsin Hydrochloride improve human sperm cell motility and function

Background and purposeAsthenozoospermia is a leading cause of male infertility, but the development of pharmaceuticals to improve sperm motility has been hindered by the lack of effective screening platforms and knowledge of suitable molecular targets. We have demonstrated that a high throughput screening (HTS) strategy in conjunction with established in vitro tests can identify and characterise the action of compounds that improve sperm motility. The study aimed to apply HTS to identify new compounds from a novel small molecule library that increase intracellular calcium, [Ca2+]I, promote human sperm cell motility and systemically determine the mechanism of action. Experimental approach A validated HTS fluorometric [Ca2+]i assay was used to screen an in-house library of compounds. Trequinsin hydrochloride (a phosphodiesterase 3 inhibitor) was selected for detailed molecular (plate reader assays, electrophysiology and cyclic nucleotide measurement) and functional (motility and acrosome reaction) testing in sperm from healthy volunteer donors and, where possible, patients.   Key resultsThe fluorometric analysis identified Trequinsin as an efficacious agonist of [Ca2+]i, although less potent than progesterone (P4). Functionally, Trequinsin significantly increased cell hyperactivation and penetration into viscous medium in all donor sperm samples and cell hyperactivation in 22/25 (88%) patient sperm samples. The Trequinsin-induced [Ca2+]i response was cross-desensitised consistently by prostaglandin E1 but not with P4. Whole-cell patch clamp electrophysiology confirmed that Trequinsin activates CatSper and partially inhibits potassium channel activity. Trequinsin also increases intracellular cGMP.   Conclusion and Implications Trequinsin exhibits a novel pharmacological profile in human sperm and may be a suitable lead compound for the development of new pharmaceuticals to improve patient sperm function and fertilisation potential

Variability in quality of white and green beans during in-pack sterilization

Non-uniformity in process quality was investigated during in-pack thermal sterilization of food products. This was accomplished through the combined application of the Monte Carlo procedure and a reliable mathematical method for process evaluation. Despite the large coefficients of variation found, the optimum quality process could be designed. The influence of the statistical variability of heating rate index on the retention of green beans color was studied and an optimum temperature range was found between 125 and 135 C. The variability in hardness of sterilized white beans, resulting from uncertainties of the combined effect of heating rate index and initial hardness of beans, was also evaluated by simulation. In this case, an optimum global temperature range between 120 and 135 C was found, independently of the rotation, F0 value and surface heat transfer coefficient assumed

Distribution of hepatitis C virus genotypes among blood donors from mid-west region of Brazil

In order to investigate the hepatitis C virus (HCV) genotypes in mid-west region of Brazil, 250 anti-HCV positive blood donors were studied. Among them, the anti-HCV serological status was confirmed in 205 (82%). HCV RNA was detected in 165 samples, which were genotyped. HCV types 1, 2 and 3 were found in 67.9%, 3% and 29.1% of the donors, respectively. In Goiás state, subtype 1a (50%) was the most prevalent, followed by subtypes 3a (30.9%) and 1b (16.7%). In Mato Grosso state, subtype 1a was also predominant (41%), followed by subtypes 1b (29.5%) and 3a (25%). In Mato Grosso do Sul state, subtypes 1a and 1b were detected equally (36.8%), followed by 3a (21.1%). Subtype 2b was rare (2.4%, 4.5% and 5.3%, respectively). In Distrito Federal, subtype 3a (39%) was more frequent than 1a (31.7%) and the remaining (29.3%) belonged to subtype 1b.Com objetivo de determinar os genótipos do vírus da hepatite C (HCV) circulantes na Região Centro-Oeste do Brasil, 250 doadores de sangue anti-HCV positivos foram estudados. Dentre eles, a positividade para anti-HCV foi confirmada em 205 (82%). O RNA-HCV foi detectado em 165 amostras, as quais foram genotipadas. Os tipos 1, 2 e 3 do HCV foram encontrados em 67,9%, 3% e 29,1% dos doadores, respectivamente. No Estado de Goiás, o subtipo 1a (50%) foi o mais prevalente, seguido pelos subtipos 3a (30,9%) e 1b (16,7%). No Estado de Mato Grosso, o subtipo 1a (41%) foi também predominante, seguido pelos subtipos 1b (29,5%) e 3a (25%). No Estado de Mato Grosso do Sul, os subtipos 1a e 1b foram igualmente detectados (36,8%), seguidos por 3a (21,1%). O subtipo 2b foi raro (2,4%, 4,5% e 5,3%, respectivamente). No Distrito Federal, o subtipo 3a (39%) foi mais freqüente que 1a (31,7%), sendo o restante (29,3%) identificado como subtipo 1b

Computational design of accelerated life testing applied to frozen green beans

Three different accelerated life tests (ALT) were designed by computer simulation to investigate their practical applicability to quantify kinetics of quality loss in frozen stored foods. Heat transfer and quality degradation inside a green bean were simulated, using a spectral finite element method (SFEM), to develop pseudo-experimental data. Temperature fluctuations inside a refrigerator were simulated, by a piecewise linear stochastic differential equation, and integrated into the SFEM program. Thereafter, the simulated data was treated by non-linear regression analysis to estimate the kinetic parameters. The different ALT tests were then compared in terms of precision and accuracy. This study shows that temperature fluctuations, inside a refrigerator, influence the accuracy of the kinetic estimates, and if the temperature spectrum is used to derive kinetic estimates, it is possible to apply accurately ALT methodologies to frozen foods