New Fining Techniques Utilizing Adsorbent Resins
To date we have evaluated the qualitative abilities of three commercially available, organophilic adsorbent resins for the purpose of removing protein-complex precursors and colored compounds from grape juice. Data have been generated towards chemically characterizing the specific amounts of protein and other constituents removed, as well as characterizing what compounds (sugars, acids, etc.) have not been removed. Resin technology appears to be promising, as the treated juice did not retain the haze forming proteins as determined in the control sample by traditional heat stability analysis and “Coomassie blue” protein analysis. The protein results are similar to those from previous efforts in which we evaluated adsorbent resins for preliminary unstable protein removal from apple juice. Resin treated juices had measured NTU values of less than 1.0 compared to a value of over 20 NTU in the non-resin treated control juice subjected to the same heat treatment. Using the “Coomassie blue” chemical analysis for proteins, over 90% of the proteins detected by this method were removed. Phenolics levels have also been reduced in the processed juices by values of 33% or 85% depending upon which resin was used. At the same time that these constituents were being removed, other data indicate essentially no changes in original Brix or pH of the juice upon being subjected to resin treatment. In separate experiments, dark colored white grape juice samples were decolorized using the three resins. These experiments were run to 100 bed volume and the degree of decolorization was quantitatively measured as %Transmittance at 430 nm. After 100 bed volumes two resins significantly improved the transmittance of the dark colored white grape juice by 20 units of %Transmittance over the starting juice. The untreated juice in this experiment had significant color and measured only 42%T. Our pilot scale studies have been conducted using 2.54 cm (1″) x 183 cm (6′) columns so that the results better reflect what would occur during production scale operations. The columns are operated using pumped flow, again to mimic production conditions. A peristaltic pump connected to the inlet line is used for delivering all juice, conditioning, and regenerating solutions.