Study of sorption properties of selected fruit fibres and pomace – PART 2
MATERIALS AND METHODOLOGY OF WORK
Characteristics of the research material
The research material was commercial fibre and fruit pomace from chokeberry, blackcurrant and apples in the form of powders obtained from GreenField Sp. z o.o. Sp. k. (Warsaw). The tested materials were uniformly finely divided in the range of 0-425 μm. Before examining the kinetics and isotherms of water vapor adsorption, the samples were dried at the temperature of 70 ° C for 24 hours with the use of a SUP-65W laboratory dryer (Wamed, Warsaw).
DISCUSSION OF THE RESULTS
General characteristics
Commercial fruit products in the form of fibres and pomace from aronia, blackcurrants and apples, the photo of which are shown in Figure 2, were tested. The color of fibres and pomace from the same fruit was similar, purple for aronia and blackcurrant, and light brown for apple products.
Table 3 shows the nutritional values of fibre from chokeberry, apples and blackcurrant. The tested materials differ in the content of some components, in particular the content of sugars and proteins.
| Nutritional values per 100g | Aronia fibre | Apple fibre | Blackcurrant fibre |
| Energy value | 111 kJ / 270 kcal | 1105 kJ / 268 kcal | 1084 kJ / 264 kcal |
| Fat – including saturated acids | 4,5 g 0,4 g | 3,2 g 0,6 g | 5,0 g 1,1 g |
| Carbohydrates -including sugars | 17,4 g 16,7 g | 24 g 13,7 g | 12 g 5,3 g |
| Fibre | 62 g | 60 g | 65,5 g |
| Protein | 9,0 g | 5,8 g | 10,5 g |
| Salt | 0 g | 0,001 g | 0 g |
WATER ACTIVITY
The water activity of the tested materials was measured to determine the initial general properties. The obtained results allowed for the conclusion that aronia fibre had the highest water activity, equal to 0.424.
| Material | Water activity |
| Aronia fibre | 0,424 |
| Apple fibre | 0,341 |
| Blackcurrant fibre | 0,324 |
| Aronia pomace | 0,321 |
| Apple pomace | 0,327 |
| Blackcurrant pomace | 0,364 |
The water activity of the pomace was similar to that of the fibres, while the water content of the pomace was significantly higher compared to the fibres. The water activity in each of the tested materials was below 0.6. It is the value of water activity below which microbial growth is impossible. This means that the pomace and fibre of selected fruits are microbiologically stable [Pałacha and Makarewicz 2011].
Master’s thesis written under the supervision of dr inż. Sabina Galus
Institute of Food Sciences
Department of Food Engineering and Production Organization
Warsaw University of Life Sciences, Poland, 2021
PART 3 under development…
Read PART 1.
