Katarzyna Rybak

The effect of pulsed electric field on drying kinetics, color, and microstructure of carrot

ABSTRACT The aim of the study was to investigate the impact of pulsed electric field (PEF) treatment on the convective drying kinetics of a carrot and color and microstructure changes of the dried product. Samples were treated by PEF with the specific energy input equal to 5.63, 8 and 80 kJ · kg−1. After PEF treatment, thermal conductivity and electrical conductivity were measured. Drying time of the PEF-treated samples was reduced up to 8.2% (Ws = 8 kJ · kg−1, 5 kV · cm−1; 10 pulses) in comparison to intact tissue. Statistical analysis showed that Midilli et al.’s model was considered to describe the kinetics of the process the most precisely. Pulsed electric field treatment increased the effective water diffusion coefficient up to 16.7%. Moreover, PEF treatment and drying caused the alteration of the sample color. After drying, the lightness and chroma were higher or unchanged in comparison to the intact tissue. The dried PEF-treated samples exhibited significantly higher redness (higher value of a* parameter) in comparison to the untreated dried samples. Moreover, the visual inspection of scanning electron microscope images revealed that PEF pretreatment performed at high electric field intensity (5 kV · cm−1, regardless of pulse number) provoked the material to form greater cavities during drying in comparison to the untreated material.

Effect of ultrasound treatment during osmotic dehydration on bioactive compounds of cranberries

HighlightsUS treatment has an impact on chemical properties of cranberries.The combination of traditional methods as cutting and blanching with US treatment was investigated.The impact of US treatment in different osmotic agent was studied.US treatment unchanged of slightly changed a bioactive compound.Traditional operation combined with US treatment caused degradation of bioactive compounds. ABSTRACT The aim of the study was to investigate the influence of ultrasound treatment applied in osmotic solution on bioactive compounds, such as vitamin C, polyphenols, anthocyanins and flavonoids content as well as antioxidant activity in cranberries (Vaccinium oxycoccus). Ultrasound treatment was performed at the frequency of 21 kHz for 30 and 60 min in two osmotic solutions ‐ 61.5% sucrose and 30% sucrose with an addition of 0.1% of steviol glycosides. Before the ultrasound treatment the material was subjected to cutting or blanching. The obtained results indicated that the influence of ultrasound waves on cranberries depends on a type of bioactive component. The ultrasound treated cranberries as well as the ones subjected to cutting or blanching enhanced by ultrasound were characterized mainly by a lower content of bioactive compounds.

Changes of Mechanical and Thermal Properties of Cranberries Subjected to Ultrasound Treatment

Abstract The aim of the study was to investigate the effect of ultrasound treatment in osmotic solution, carried out at different time and solutions, on mechanical and thermal properties of cranberries. Ultrasound treatment was applied for 30 and 60 min in liquid mediums such as 61.5 % sucrose solution and 30 % sucrose solution with 0.1 % steviol glycosides addition. Before the ultrasound treatment samples were subjected to traditional operations (cutting, blanching). The traditional operations and ultrasonic treatment of whole fruits did not influence or slightly influenced dry matter content and mechanical properties. The cutting had impact on thermal properties to the highest extent due to the exposition of fruits’ flesh. The combination of cutting and sonication decreased thermal conductivity which suggests that mass transfer was more pronounced. The sonication had greater influence when compared to only ultrasonic treatment. Combined both cutting and blanching with ultrasonic treatment led to greater changes in cranberries properties.

Postharvest Monitoring of Tomato Ripening Using the Dynamic Laser Speckle

The dynamic laser speckle (biospeckle) method was tested as a potential tool for the assessment and monitoring of the maturity stage of tomatoes. Two tomato cultivars—Admiro and Starbuck—were tested. The process of climacteric maturation of tomatoes was monitored during a shelf life storage experiment. The biospeckle phenomena were captured using 640 nm and 830 nm laser light wavelength, and analysed using two activity descriptors based on biospeckle pattern decorrelation—C4 and ε. The well-established optical parameters of tomatoes skin were used as a reference method (luminosity, a*/b*, chroma). Both methods were tested with respect to their prediction capabilities of the maturity and destructive indicators of tomatoes—firmness, chlorophyll and carotenoids content. The statistical significance of the tested relationships were investigated by means of linear regression models. The climacteric maturation of tomato fruit was associated with an increase in biospckle activity. Compared to the 830 nm laser wavelength the biospeckle activity measured at 640 nm enabled more accurate predictions of firmness, chlorophyll and carotenoids content. At 640 nm laser wavelength both activity descriptors (C4 and ε) provided similar results, while at 830 nm the ε showed slightly better performance. The linear regression models showed that biospeckle activity descriptors had a higher correlation with chlorophyll and carotenoids content than the a*/b* ratio and luminosity. The results for chroma were comparable with the results for both biospeckle activity indicators. The biospeckle method showed very good results in terms of maturation monitoring and the prediction of the maturity indices of tomatoes, proving the possibility of practical implementation of this method for the determination of the maturity stage of tomatoes.

Selected chemical composition changes in microwave-convective dried parsley leaves affected by ultrasound and steaming pre-treatments – An optimization approach

Parsley leaves contain a high amount of bioactive components (especially lutein), therefore it is crucial to select the most appropriate pre-treatment and drying conditions, in order to obtain high quality of dried leaves, which was the aim of this study. The optimization was done using response surface methodology (RSM) for the following factors: microwave power (100, 200, 300W), air temperature (20, 30, 40°C) and pre-treatment variant (ultrasound, steaming and dipping as a control). Total phenolic content (TPC), antioxidant activity, chlorophyll and lutein contents (using UPLC-PDA) were determined in dried leaves. The analysed responses were dependent on the applied drying parameters and the pre-treatment type. The possibility of ultrasound and steam treatment application was proven and the optimal processing conditions were selected.

Application of various types of coatings in food packaging materials: Sensorial assessment and health safety

Food safety is a crucial aspect, when designing food packaging. It is necessary to assess every layer of the material that could be interacting with food. There are various substances that could be used to produce coatings for the cardboard materials, safe for the application in the food packaging materials. By introducing additional layer to the packaging material, it is possible to enhance food safety, improve packaging and food quality, and extend food shelf-life. The aim of this work is to present the background of some applications of paper coatings based on proteins, polysaccharides, lipids and others. Moreover the food safety aspect of paper and cardboard was described.