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Progress in Agricultural Engineering Sciences
Authors:
Dávid Nagy
,
Viktória Zsom-Muha
,
Csaba Németh
, and
József Felföldi

Abstract

The aim of this study was to determine the effect of ultrasound treatment on foaming properties of egg white. The samples were sonicated at 20/40 kHz and 180/300 W equipment power (3.7/6.9 W absorbed power) for 30, 45 and 60 minutes. Foam capacity had been increased by 25% due to sonication at 40 kHz and 6.9 W absorbed power for 60 minutes. This phenomenon may be caused by the homogenization effect of ultrasound and protein exposure of hydrophobic groups that improve the adsorption of protein onto the air/water interfacial molecules. It is found that frequency and duration of the treatment have no significant impact on the changes in foam capacity, only the absorbed power. On the other hand, foam stability had been decreased during the ultrasonic treatment. We can assume that sonication decreases the potential difference between the dispersed particles and the dispersion medium and this may be the cause of the collapse of the foam structure due to ultrasound treatment. In this case frequency, treatment time, and the absorbed power had a significant effect on the stability.

Open access
Progress in Agricultural Engineering Sciences
Authors:
Katalin Badak-Kerti
,
Viktória Zsom-Muha
,
Tamás Zsom
,
Dávid Nagy
, and
József Felföldi

Abstract

In the experiments, the sound generated during the breaking of chocolate samples was examined. The fracture was performed by a precision penetrometer, the breaking sound was recorded. Texture index (TI) was calculated from the resulting signal. First the change of the resulting TI was monitored as a function of the samples' temperature. The sample groups of the same dark chocolate with different temperatures were completely separated from each other with statistical tool (LDA, linear discriminant analyses), but no trend was found to describe the change. Secondly, based on the TI, we could identify and classify the chocolate samples in the appropriate groups (based on cocoa content from 40 to 85%). According to linear discriminant analyses chocolates with different cocoa content were completely separated and showed a certain pattern. Based on the obtained results, it can be stated that the cocoa content of chocolate can be determined on the basis of TI obtained by acoustic method.

Open access
Progress in Agricultural Engineering Sciences
Authors:
Tamás Zsom
,
Viktória Zsom-Muha
,
Lien Phuong Le Nguyen
,
Dávid Nagy
,
Géza Hitka
,
Petra Polgári
, and
László Baranyai

Abstract

Application of cold storage temperatures below optimum induces a high risk and threat of chilling injury (CI) in the case of sensitive commodities. Sweet pepper belongs to this group of vegetables, so our main objective was to investigate and monitor the effect of non-optimal temperatures (2.5 and 5 °C) induced stress (chilling injury) on kápia type sweet pepper (Capsicum annuum L.) during its postharvest storage by nondestructive quality measuring methods. Fresh, semi-matured (reddish-green colored) samples of ‘Kapitány F1’ cultivar were stored at 2.5, 5 and 10 °C for 7 d followed by 7 d shelf-life. Nondestructive texture measurements were carried out by a purpose built tabletop acoustic stiffness device. Surface color and chlorophyll content related quality indices were evaluated by a chroma meter, a DA-meter® and a chlorophyll fluorescence imaging system. High resolution digital pictures were captured and analyzed for possible CI defects by means of surface color values (normalized RGB, hue and saturation). According to our results, the evaluated quality indices (DA-index®, acoustic stiffness coefficient, surface color parameters; F0, Fm, Fv and Fv/Fm chlorophyll fluorescence parameters) clearly represented the temperature dependent quality changes during low temperature storage, subsequently followed by ambient shelf-life. Samples stored under and at 5 °C showed the chilling temperature stressed symptoms of delayed and partly retarded postharvest ripening, even under simulated shelf-life conditions, but without the onset and manifestation of the characteristic visible symptoms of chilling injury. This may raise doubts and suggest possible future research areas regarding the role of non-optimal cold storage temperatures induced stress, the effect of chilling injury contributing factors and consequences.

Open access