Study of sorption properties of selected fruit fibres and pomace – PART 2


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).


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.

Figure 2

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 100gAronia fibreApple fibreBlackcurrant fibre
Energy value111 kJ / 270 kcal1105 kJ / 268 kcal1084 kJ / 264 kcal
Fat – including saturated acids4,5 g 0,4 g3,2 g 0,6 g5,0 g 1,1 g
Carbohydrates -including sugars17,4 g 16,7 g24 g 13,7 g12 g 5,3 g
Fibre62 g60 g65,5 g
Protein9,0 g5,8 g10,5 g
Salt0 g0,001 g0 g
Table 3


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.

MaterialWater activity
Aronia fibre0,424
Apple fibre0,341
Blackcurrant fibre0,324
Aronia pomace0,321
Apple pomace0,327
Blackcurrant pomace0,364

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.