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High hydrostatic pressure (HHP) technology, as a promising alternative of thermal-treatment and chemical preservatives, can be used to produce minimally processed foods. It has the advantage of affecting only non-covalent bonds of macromolecules in foods, and thus preserves nutritional components, taste, and flavour exceptionally well. However, HHP also influences enzymatic reactions of food. Although some of these changes are often beneficial, monitoring the potential effects of high pressure treatments — especially in the field of product and technology development — is essential. The aim of this study was to point out some parameters of high hydrostatic pressure technique (pressure, temperature, build-up time, holding time, number of cycles) that can substantially impact the sensory properties of treated products.

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Applying antagonistic yeasts is one of the recent possibilities for controlling postharvest disease caused by blue mould (Penicillium expansum). In this work, antagonistic activity of several Kl. lactisstrains was tested against two strains of P. expansum. Three strains of Kl. lactiswere compared to three biocontrol yeasts: Metschnikowia pulcherrima, Sporobolomyces roseusand Pichia anomala. The investigations were carried out at 25 °C, 15 °C and 5 °C, applying different yeast cell densities and culture media. Statistical analysis showed no significant differences among the three Kl. lactisstrains. The inhibitory effect of the tested yeasts was different according to the applied mould strain temperature, culture medium and cell density. Application of antagonistic yeasts combined with reduced temperature enhanced the inhibitory effect. Direct relationship was observed between increasing cell density and the biocontrol efficiency of Kl. lactis. According to this work, Kl. lactisis a possible biocontrol agent.

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Acta Alimentaria
Authors:
A. Taczman-Brückner
,
Cs. Mohácsi-Farkas
,
Cs. Balla
, and
G. Kiskó

Numerous yeasts are reported as being effective in controlling plant pathogenic moulds. By selecting new biocontrol agents, knowledge about the mode of action of mould inhibition is important. In our study, mode of action of Kluyveromyces lactis - successfully applied against Penicillium expansum in former studies - was investigated. According to the results, volatile compounds are supposed to play a role in restriction of mould growth. Antibiotic substances and killer toxins produced by the tested Kl. lactis strain were not detected.

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Water content of dry sausages may decrease due to improper ripening and storage as well. As a consequence, an outer crust appears on the surface of the products. The aim of the industry is either to eliminate the presence of outer crust, or decrease its occurrence. The thickness of outer crust can be estimated by non-destructive ultrasound technique. As the propagation time and attenuation of ultrasonic waves vary in the materials with different water content, the thickness of outer crust and the normal texture, respectively, can be estimated on the basis of these characteristics. The propagation and attenuation values are typical for the given layers. Thus, by measuring total attenuation and total width of the product, the thickness of outer crust can be calculated by means of the velocity and attenuation coefficients of ultrasonic waves. Results of this non-destructive measurement may support the proper adjustment of ripening and storage parameters such as temperature and humidity.

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1-Methylcyclopropene (1-MCP) is the active component of the SmartFresh Quality System. By the application of the 1-MCP compound, quality of the harvested pears can be preserved longer during the normal cold storage. In our work, the effectiveness of the SmartFresh Quality System was investigated on ‘Bosc Kobak’ pears (Pyruscommunis L.) harvested at different times. The rheological changes and storage losses were measured. The effectiveness of 1-MCP depends on many variables, but our results show that the optimal harvest date and the condition of the harvested fruit are the most influential factors.

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In this study, pressed apricot (Prunus armeniaca L.) juice was concentrated using complex membrane technology with different module combinations: UF-RO-OD, UF-RO-MD, UF-NF-OD and UF-NF-MD. In case of the best combination a cross-flow polyethylene ultrafiltration membrane (UF) was applied for clarification, after which preconcentration was done using reverse osmosis (RO) with a polyamide membrane, and the final concentration was completed by osmotic distillation (OD) using a polypropylene module. The UF-RO-OD procedure resulted in a final concentrate with a 65-70 °Brix dry solid content and an excellent quality juice with high polyphenol content and high antioxidant capacity.Nanofiltration (NF) and membrane distillation (MD) were not proper economic solutions.The influence of certain operation parameters was examined experimentally. Temperatures of UF and RO were: 25, 30, and 35 °C, and of OD 25 °C. Recycle flow rates were: UF: 1, 1.5, and 2 m3 h−1; RO: 200, 400, and 600 l h−1; OD: 20, 30 and 40 l h−1. The flow rates in the module were expressed by the Reynolds number, as well. Based on preliminary experiments, the transmembrane pressures of UF and RO filtration were 4 bar and 50 bar, respectively. Each experimental run was performed three times. The following optimal operation parameters provided the lowest total cost: UF: 35 °C, 2 m3 h−1, 4 bar; RO: 35 °C, 600 l h−1, 50 bar; OD: 20, 30 and 40 l h−1; temperature 25 °C.In addition, experiments were performed for apricot juice concentration by evaporation, which technique is widely applied in the industry using vacuum and low temperature.For description the UF filtration, a dynamic model and regression by SPSS 14.0 statistics software were applied.

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The aim of the present study was to examine the infuence of hydrolyzed, nanofltered concentrate of the ultrafltered permeate (HNF concentrate) of acid whey on the quality characteristics of milk-based ice cream. Thermophysical properties were determined by differential scanning calorimeter, consistency was measured by oscillatory rheometer, and sensorial quality was evaluated by scoring method. It was concluded that the acid whey did not increase the melting of the product, and reduced the freezing point. Cryoscopic temperature, onset point, and glass transition temperature (Tg) gradually decreased as the quantity and proportion of acid whey increased in the ice-cream. Rheological results indicated that using HNF, acid whey produced more creamy and smooth ice-cream. However, because of its characteristic taste, maximum 20% of milk could be replaced by HNF acid whey in milk-based ice-creams.

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The aim of the study was to select the most suitable freezing and thawing method for preserving the quality of pasta flata type Parenica cheese comparing different methods: slow, shock (circulated air) and cryogenic freezing and thawing at room temperature and in a refrigerator, respectively. To observe the effects of these methods on some cheese properties weight, pH, and dry-matter content were measured, stringiness was examined, and compression test were performed for texture analysis. Thermophysical properties were determined by DSC: unfreezable water content, onset point of melting, and latent heat. Sensory analyses were also carried out by profle analysis. Results of objective and subjective measurements showed similar trends: characteristics of cheese samples frozen in circulated air and thawed in refrigerator resembled the most to the control sample.

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The fat content (fat distribution) of the pork and beef raw material is one of their most important quality characteristics. Image processing methods were applied to provide with quantitative parameters related to these properties. Different hardware tools were tested to select the appropriate imaging alternative. Statistical analysis of the RGB data was performed in order to find appropriate classification function for segmentation. Discriminant analysis of the RGB data of selected image regions (fat-meat-background) resulted in a good segmentation of the fat regions. Classification function was applied on the RGB images of the samples, to identify and measure the regions in question. The fat-meat ratio and textural parameters (entropy, contrast, etc.) were determined. Comparison of the image parameters with the sensory evaluation results showed an encouraging correlation.

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Acta Alimentaria
Authors:
L. Darnay
,
A. Dankovics
,
B. Molnár
,
L. Friedrich
,
Gy. Kenesei
, and
Cs. Balla

Several scientific papers suggest that microbial transglutaminase (mTG) is capable of reducing the salt content of cured and/or heat-treated meat products (ham, frankfurters, meat ball). These scientific results are not widely known in Hungary, and as a result of this, only little experience was gathered in our meat industry. According to this lack of knowledge, our aim was to lower the curing salt to a still microbiological safe level using mTG by frankfurters, one of the most well-known heat treated meat products in Hungary. The observed technofunctional properties suggest to use mTG enzyme preparation at 0.5% concentration. This enzyme dosage can reduce the average 1.8% salt content to 1.6% and it also may contribute to extended shelf life of popular frankfurters. Our sensorial analysis revealed that the panellists have not found a loss in quality between 1.4% and 1.6% salt.

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