Presentation on theme: "Lee R. Madsen II, Research Associate † /Doctoral Student ‡ † LSU AgCenter, ‡ LSU Dept. of Chemistry Funded in part by: the Louisiana Board of Regents,"— Presentation transcript:
Lee R. Madsen II, Research Associate † /Doctoral Student ‡ † LSU AgCenter, ‡ LSU Dept. of Chemistry Funded in part by: the Louisiana Board of Regents, the American Sugarcane League and Cargill, N.A.
Left, syrup diluted to 32%bx Right, decolorized syrup diluted to 32%bx A, without Iron; B, with Iron Things Were not looking good…
Left, Caffeic acid with varying amounts of iron added Right, Caffeic acid and glutamine with varying amounts of iron Amino Acids React with Phenolics in the Presence of Iron 77 g/mL
Eureka! Why was this leading to an increase in color? The complexes formed are highly colored and polymerization via Fe is relatively slow. Result? Highly colored molecules that are too small to ppt. Maybe the free NH 2 groups on the protein in the raw juice might react with Fe complexed phenolics, causing the adducts to precipitate (ppt). When tested on Raw juice, we saw rapid ppt. with a concomitant removal of color.
The Goods: Left, Mixed Juice clarified normally Right, DC juice, treated with 400 mg/kg ds Fe 3+ and then hot-limed normally
How we are doing this: The raw juice is treated with Fe at ambient temperature (20-30°C). Cationic flocculant increases the settling rate significantly, but is not required if this is run hotter*. The first stage is settled and decanted then is subject to hot-liming with anionic flocculant (5 ppm max.) * Greater density gradient, but is limited by iron dosage, discussed later.
Fe g/g: 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 1000 Iron in Juice: There is a threshold on iron concentration where flocculation/ decolorization is most efficient. Raw juice, settling, top. Raw juice, decanted, bottom.
The Fine Print The method works well and can eliminate in excess of 70% of the colored materials expressed from cane. Higher temperatures lead to run-away color formation. The upper temp. is dictated by the amount of iron applied. It appears to be reliable only with good juice. Juice that is badly deteriorated (microbially) is made worse. Why?
How Does This Work? The hypothesis: The phenolic materials are oxidized by iron/O 2 and couple to free NH 2 groups on the protein. These protein:phenolic adducts can precipitate. In order to help verify this, the system was “reverse-engineered” from raw sugar “melts”.
How Does This Work? Using BSA and Fe it was found that CFA can be made to precipitate quantitatively from water. In solutions of raw sugar, the behavior is not straight-forward. It was found that acetate, applied as AcONa/AcOH(1M) is required for flocculation
mg/kg protein in juice* Total Acidic Phenolics ave. 250 mg/kg in juice* ~7000 mg/kg monocarboxylic acids in juice* *Van der Poel, P.W., Schiweck, H. and Schwartz, T. Sugar Technology: Beet and Cane Sugar Manufacture. (1998). ISBN X. pp
Take Home Messages: For color ppt. to occur there must be a certain amount of 1) protein, 2) phenolic material, 3) iron and 4) organic acid. Fortunately, the optimized values are close to what is normally found in juice— Unless… the juice is bad; this leads to a drop in pH and along with it, the ppt of protein. Eliminating this component likely explains why the method failed with deteriorated juice.
Thank you For Playing! Funded in part by: the Louisiana Board of Regents, the American Sugarcane League and Cargill, N.A.