Browsing by Subject "ultrafiltration"

Apples are one of the most eaten and processed fruits in the world. For example, in apple juice production, proportion of the main side stream, apple pomace is 25–35%. It contains mainly carbohydrates and little bit of protein and fat, which makes it unsuitable for feed purposes. Nevertheless, carbohydrates are commonly extracted by water extraction for further purposes of use. Membrane separation is an interesting possibility to fractionate molecules of different sizes from aqueous solutions, for example with ultrafiltration (UF) lactose is separated from whey in dairy industry. Advantages of membrane separation include low energy consumption, low environmental impacts and no phase change. Main limitation for the use of membrane separation process is fouling of membranes, which means that there is a decrease in permeation as a function of time. Aims of the study were to 1) optimize parameters for the membrane separation method by using model solutions in order to get good yield from the process and to 2) separate carbohydrates from apple pomace using water extraction and membrane separation method. Model solutions were used for determining of UF functionality. Sucrose model solutions (SMS) had three different concentration 1, 6 and 11% and pectin-sucrose model solutions (PSMS) had the same concentrations with a pectin addition of 0.5%. These were used to optimize transmembrane pressure (TMP) and concentration for apple pomace extract runs. Apple pomace originated from mixed variety of Finnish apples. Apple pomace was stored in freezer until needed. It was first homogenized by a colloid mill, and carbohydrates were extracted with water extraction in three different apple pomace to water ratios (w/w) with constant extraction time and temperature (80 min/30 ˚C). Three parallel extractions and UF runs were performed for each of the ratios (1:30, 1:10, 1:2 double extraction). Based on the results of the UF runs of model solutions TMP of 4.5 bar was applied for these runs. Samples were taken from original feed solution (weighed solution without the water from the equipment), running solution (after 5 min relaxation time, includes the water from the equipment), permeate and retentate, and from these sugars were analysed with UPLC, dry matter was determined by freeze drying and flux and fouling were calculated. Lower concentration and higher pressure resulted in higher flux (L m-2 h-1) in UF. Presence of bigger compounds, such as pectins, slowed down the experiment and thus, flux. Apple pomace extract runs followed the same principal of higher concentration leading into slower process. The yield of water extraction from dry matter in apple pomace varied between 35 to 65%, the highest yield originated from the pomace to water ratio of 1:30 (w/w). Sugar analysis showed that the permeate from apple pomace extracts contained mostly fructose (average in all of the nine runs 57.4% ± 1.8), sucrose (21.8% ± 3.9) and a little bit of glucose (13.3% ± 1.2) and malic acid (7.4% ± 2.2). In summary, combination of efficient homogenization of raw material by a colloid mill, conventional water extraction and UF of water extract proved to be successful for carbohydrate extraction from apple pomace. Modelling concluded that lower concentration and/or higher pressure leads into higher flux in the process. The whole UF process is slower if there is pectin in the feed solution.