1) Tausta ja tavoitteet
In this research work the focus was on developing technologies for the avoidance of food waste in the processing of blackcurrant berries from two aspects. Firstly, membrane technologies including ultrafiltration and reverse osmosis was implemented in the juice concentrate production with the aim to carry out the concentration at mild processing conditions since the valuable compounds of the blackcurrants are heat and processing sensitive.
Secondly, in the blackcurrant pressing process, the press-cake stays behind as a by-product of processing. The current practice in small and medium scale companies is to utilize this by-product as a fertilizer or animal feed. However, the press-cake that contains the peels, the pomace and the seeds of the blackcurrants can be valorized to extract anthocyanins and pectins in the microwave-assisted process.
The juices are first depectinized using commericial enzyme preparation with the aim to enhance the filtration efficiency that is measured through the permeate flux. An optimal enzyme concentration is determined which increases the permeate flux during the ultrafiltration. Since the valuable compounds are processing sensitive, the amount of anthocyanins and flavonols are measured in the filtration process. The major role of ultrafiltration is to clarify the blackcurrant juice, and therefore to increase the efficiency of the concentration process in reverse osmosis.
In the extraction of anthocyanins from blackcurrant press-cake a special attention is given to the effect of the different process variables for the final concentration of anhocyanins in the extracts. Such process parameters were the amount of solvent used, the pH of the solvent, specific microwave power and the time of the extraction. The implementation of response surface methodology in the experiments makes it possible to determine the optimal processing parameters for the maximum recovery of anthocyanins.
The doctoral dissertation will be a compendium of a summary article and 4 published articles. The summary article will contain the theoretical background of the research, a comprehensive review of the related literature, and the outline of the scientific contribution of the doctoral research.
List of published peer-reviewed journal articles:
Article 1:Pap N, Mahosenaho M, Pongrácz E, Mikkonen H, Jaakkola M, Virtanen V, Myllykoski L, Horváth-Hovorka ZS, Hodúr C, Vatai Gy and Keiski RL (2012). Effect of ultrafiltration on anthocyanin and flavonol content of black currant juice (Ribes nigrum L.). Food and Bioprocess Technology 5 (3): 921-928.
Article 2:Pap N, Kertész Sz, Pongrácz E, Myllykoski L, Keiski RL, Vatai Gy, László Zs, Beszédes S and Hodúr C (2009). Concentration of blackcurrant juice by reverse osmosis. Desalination, 241(1-3): 256-264.
Article 3:Pap N, Pongrácz E, Jaakkola M, Tolonen T, Virtanen V, Turkki A, Horváth-Hovorka ZS, Vatai GY and Keiski RL. (2010). The effect of pre-treatment on the anthocyanin and flavonol content of black currant juice (Ribes nigrum L.) in concentration by reverse osmosis. Journal of Food engineering 98 (4): 429-436.
Article 4:Pap N, Beszédes S, Pongrácz E, Myllykoski L, Gábor M, Gyimes E, Hodúr C and Keiski RL (2013). Microwave-Assisted Extraction of Anthocyanins from Black Currant Marc. Food and Bioprocess Technology 6 (10): 2666-2674.
4) Vaikuttavuus ja käytäntöön vienti
This research work reported on the complete utilization of blackcurrant berries for juice concentrate production, and to obtain anthocyanins as a co-product. The study investigated how the different pre-treatment methods, e.g. clarification and enzymatic treatment can increase the efficiency of the concentration process. The concentration process was carried out in a pilot scale, therefore its scale-it up can be easily carried out to the needs of small and medium size companies.
This research also indicated that the utilization of the by-products by the proper technology could benefit the companies with more valuable final products then feed or fertilizer, in products that have high anthocyanin content, and can be obtained using novel extraction technologies rather than conventional extraction methods. Therefore, the processing of the by-product may also have a positive effect on the economy of the berry processing companies, since the processing results in products that have higher economical value as the feed or fertilizer.
University of Oulu, Marjarannikko Oy, Fitomark 94 Ltd., Hungary