Justino Burgos

The effects of manothermosonication on tomato pectic enzymes and tomato paste rheological properties

The effect of manothermosonication (MTS), the simultaneous application of heat and high energy ultrasound waves under moderate pressure, on tomato juice rheology and on tomato pectinmethylesterase (PME) and polygalacturonase (PG) activity in tomato juice was examined. Tomato juice was subjected to MTS treatments (20 kHz, 2 kg pressure, 117 μm amplitude and 70 °C), or to control thermal treatments (TT), for 1 min. Flow curves, yield stress and apparent viscosity were measured on both kind of samples. Apparent viscosity of MTS samples were 1.6-fold higher than that of TT samples. Yield stress values were also 2.2-fold higher in MTS than in TT samples. Flow curve values were fitted to the power law equation; MTS samples showed about 1.9-fold higher consistency values and lower flow indexes, n=0.190 vs. n=0.126, than TT samples. MTS samples retained about 20% more serum than TT samples after centrifugation. TT inactivated about 38% of the initial PME activity whereas PME activity was undetectable in MTS-treated tomato juice. TT left PG unaffected whereas MTS treatments inactivated 62% of total PG activity. These results suggest, that MTS could be an useful technology to obtain high viscosity and consistency tomato juice.

Inactivation of proteases and lipases by ultrasound

The inactivation of phospholipase A2, α-chymotrypsin, trypsin and porcine pancreatic lipase by heat and manothermosonication (MTS), and the simultaneous application of heat and ultrasound under moderate pressure, has been studied in different treatment media. MTS sensitivity varied strongly for the different enzymes. Whereas phospholipase A2 was almost insensitive to MTS treatments, α-chymotrypsin and porcine lipase MTS inactivation was much faster than heat inactivation. Trypsin heat inactivation was very different at low than at high temperatures. At low temperatures, it did not follow first order kinetics, contrary to what happened at high temperatures. MTS accelerated trypsin inactivation only at low temperatures. MTS changed also the inactivation order of trypsin (at low temperatures), α-chymotrypsin and porcine lipase; whereas heat inactivation of these enzymes did not follow first order kinetics, MTS inactivation fitted this well.

Use of modified atmospheres to prolong the postharvest life of Burlat cherries at two different degrees of ripeness

The effects of degree of ripeness and packaging atmosphere on the quality of the very early season cherry (Prunus avium) cultivar ‘Burlat’ have been studied. Cherries were classified into two groups depending on their stage of ripening, taking colour as a maturity index (red and purple). After rapid chilling, cherries were sealed in 50 µm low-density polyethylene (LDPE) bags in four different atmosphere compositions. Packages were stored at 2 °C and cherries were analysed weekly until they were deemed to be commercially unacceptable (after 4 weeks for red cherries and 3 weeks for purple cherries). Changes in atmosphere composition, skin colour, pigment content, titratable acidity, soluble solids, firmness and sensory quality were monitored. Acceptability was higher for the less mature group of cherries. Colour shifted in both groups, initially from red to blue/red and later on back to red. Titratable acidity decreased at the end of the experimental period for all samples. Firmness increased at first, but towards the end of the experiment it was similar to the initial value. The gas composition of the four modified atmosphere conditions approached a final equilibrium consisting of 9–12% CO2 and 1–3% O2. For long-distance transportation of Burlat cherries the following procedure is recommended: harvest at the red colour stage, package in air using LDPE bags and maintain the temperature at 2 °C. Under these conditions, red Burlat cherries can be kept in an excellent commercial state for 3 weeks. © 2000 Society of Chemical Industry

Free radical production by manothermosonication

Abstract The use of manothermosonication (MTS), a combined treatment of heat and ultrasound (20 kHz frequency) under moderate pressure, has been recently proposed as an alternative to conventional heat treatment of liquid foods. The efficiency of MTS has been proved on several enzymes of interest in food industry. One of the MTS enzyme inactivation mechanisms proposed is the interaction of free radicals produced by water sonolysis with some amino acid residues. In this paper we examine the rate of free radical production of the MTS system under different conditions of temperature, pressure and ultrasound amplitude using the terephtalate dosimeter. The ultrasound amplitude was varied between 20 and 145 μm at two different temperatures and pressures ( 70 ° C 200 kPa and 130 ° C 500 kPa ). In both cases, free radical production rate increases linearly with increasing ultrasound amplitude. The pressure effects on free radical production was studied under two different conditions at 117 μm: 70 °C and 130 °C. At 70 °C an increase of hydrostatic pressure results in an increase in free radical production rate, whereas increasing hydrostatic pressure at 130 °C had a negligible effect on free radical production rate. Temperature effects were studied between 30 and 140 °C at 117 μm ultrasound amplitude. Results show that increasing temperature results in a decrease in hydroxyl radical rate production.

Manothermosonication of heat-resistant lipase and protease from Pseudomonas fluorescens: effect of pH and sonication parameters.

The effect of different parameters (pH, ultrasonic amplitude and pressure) on the resistance to heat and manothermosonication (MTS) treatments of heat resistant lipase and protease produced by Pseudomonas fluorescens B52 and NCDO 2085, respectively, were studied. Lipase B52 thermoresistance decreases with an increase of pH. However, inactivation by MTS seems to be pH independent. There were only slight increases in the MTS efficiency when increasing pressure at UHT temperatures and the effect of amplitude was different depending on treatment temperature. Protease NCDO 2085, which was very resistant to MTS at 30 degrees C. was very sensitive to MTS at 76 degrees C. Increases in applied pressure had no effect on MTS efficiency at 140 degrees C and its inactivation by MTS was almost temperature independent between 76-109 degrees C. Data obtained are compared with previous published data and inactivation mechanisms are discussed.

Temperature dependence of lipoxygenase heat inactivation; evaluation with linearly increasing temperature profiles

ZusammenfassungEine nicht isotherme kinetische Methode zur Bewertung der Temperaturabhängigkeit der Hitzeinaktivierung von Enzymen wurde aus theoretischen Grundlagen entwickelt. Mittels eines nicht linearen Regressions-Computerprogrammes und Enzymaktivitätbestimmungen entlang linear steigender Temperaturprofile wurden z-Werte von Lipoxygenase in einzelnen Versuchen bestimmt. Auf diese Weise werden Zeit, Kosten und Laborarbeit erspart. Die so bestimmten z-Werte waren von der Erhitzungsgeschwindigkeit leicht abhängig; z-Werte von 4,11 °C bis 4,66 °C wurden bei Erhitzungsgeschwindigkeiten von 2,56 °C/Minute bzw. 1,48 °C/Minute bestimmt.AbstractA non-isothermal kinetic method for evaluating the temperature dependence of enzyme heat inactivation has been developed from theoretical considerations. By using a non-linear regression software programme and enzyme activity data obtained along linearly increasing temperature profiles, z values of lipoxygenase were obtained in single experiments, substantially reducing time, cost, and labour. The z values so obtained were slightly dependent on heating rate, varying from 4.11° C at a rate of heating of 2.56° C/min to 4.66° C at a heating rate of 1.48° C/min.

MINIMAL METHODS OF PROCESSING | Manothermosonication

This article is a revision of the previous edition article by Justino Burgos, volume 2, pp 1462–1469,