Inga Klimczak

Książka z zakresu współczesnej technologii przetwórstwa surowców na produkty akceptowalne przez konsumentów. Poświęcona zagadnieniu enzymatycznego brązowienia mętnego soku jabłkowego, prezentuje badania na temat możliwości wykorzystania na przykład ekstraktów z roślin czy innych soków do przedłużania trwałości mętnych soków jabłkowych w aspekcie ich barwy. Badania te wpisują się w nurt dotyczący roli naturalnych przeciwutleniaczy jako inhibitorów brązowienia enzymatycznego.

Due to the considerable competition on fruit and vegetable preserves market, the quality of juices, and primarily their sensory characteristics have become, together with price, a fundamental factor influencing purchasing decisions of consumers. It is very important to ensure appropriate sensory quality of juices by maintaining the standard conditions of their storage, bearing in mind the long shelf life of juices – usually 12 months from the production date. The objective of the present study was to determine the influence of storage conditions on the sensory quality of orange juices marketed domestically under two popular brands. The sensory quality of the juices stored at 18oC for 12 months corresponded to the quality of these stored 2 months at 28oC. At 38oC, the juices were completely changed after 2 months and were unfit for drinking.

Plants represent a potential source of new compounds with high antioxidant activity as they produce significant amount of antioxidants to prevent the oxidative stress caused by photons and oxygen. These components not only have a positive health impact but also increase food stability. Finding natural products with potentially high content of antioxidants and antioxidant activity is desired. Therefore, the aim of our study was to investigate total phenolics content and antioxidant activity in three different plants depending on sample preparation and extraction methods. Fully ripened wild rose (Rosa canina), quince (Cydonia oblonga) and mahonia (Mahonia aquifolium) were collected in gardens in Poznań area. Ethanol in three different compositions with water was used to extract components from blended or pulped fruits. The concentration of total phenolic compounds in obtained extracts was measured by Folin-Ciocalteu procedure. Extraction with 80% ethanol, both form blended and pulped ...

Enzymatic browning is a major problem in the production of fresh cloudy apple juice and is caused by the activity of polyphenol oxidase (PPO). This phenomenon is the cause of shortening the shelf life of-juices and decreasing its nutritional value. The most commonly method used to inhibit browning reaction is the application of natural inhibitory agents. Therefore, the aim of our study was to evaluate the effect of pomegranate juice on the enzymatic browning of fresh, cloudy apple juice. Pomegranate fruit (Punica granatum L.) and their products have recently attracted much attention for its health benefits due to their antioxidative properties, which are highly correlated with their polyphenol content. Freshly prepared, cloudy apple juice was obtained from the local juice manufacture. Samples contained cloudy apple juice (unpasteurized) with the addition of pomegranate juice in amount of 25, 35 and 50%, were prepared in the laboratory. All juices were stored for 48 hours at 4°C. The...

Ultra performance liquid chromatography (UPLC) and high-performance liquid chromatography (HPLC) methods for determination of ascorbic acid (AA) and total AA (TAA) contents (as the sum of AA and dehydroascorbic acid (DHAA) after its reduction to AA) in fruit beverages and in pharmaceutical preparations were compared. Both methods are rapid: total time of analysis was 15 and 6 min for HPLC and UPLC methods, respectively. The methods were validated in terms of linearity, instrument precision, limits of detection (LOD) and quantification (LOQ), accuracy and recovery. Intra- and inter-day instrument precisions for fruit juices, expressed as RSD, were 2.2% and 2.4% for HPLC, respectively, and 1.7% and 1.9% for UPLC, respectively. For vitamin C tablets, inter- and intra-day precisions were 0.4% and 0.5%, respectively (HPLC), and 0.5% and 0.3%, respectively (UPLC). Both methods were sensitive: LOD was 0.049 μg/mL for HPLC and 0.024 μg/mL for UPLC while LOQs were 0.149 and 0.073 μg/mL for HPLC and UPLC, respectively. These methods could be useful in the routine qualitative and quantitative analysis of AA or TAA in pharmaceutical preparations or fruit beverages. However, UPLC method is more sensitive, faster and consumes less eluent.

The effect of time and temperature on the content of vitamin C, total polyphenols and individual phenolic compounds as well as on the antioxidant activity of two commercial orange juices was studied. The polyphenol content was determined using Folin–Ciocalteu and HPLC methods. The two methods, SPE versus direct injection following a simple treatment of samples, were compared to assess two