WORLD PULP&PAPER 63 We can significantly decrease the degradation of both fresh and recycled starch by inhibiting the action of amylase enzyme. We can significantly decrease the degradation of both fresh and recycled starch by inhibiting the action of amylase enzyme. By optimising the retention program with a dedicated polymer, the non-degraded recycled starch can be retained into fibres giving the extra strength and increasing the grammage with same fibre usage.   METHODS Pulp Preparation European testliner board was used as the raw material. This testliner contained about 5% surface size starch (enzymatically degraded native corn starch). Testliner board was cut to 2cm x 2cm squares. Dilution water was made from tap water by adjusting Ca2+ concentration to 520mg/l by CaCl2 and by adjusting conductivity to 4 mS/cm with NaCl. 2.7 l of dilution water and heated to 85°C. The pieces of testliner were soaked for 5 minutes in dilution water at 2% concentration before disintegration. Slurry was disintegrated in a Britt jar disintegrator with 30,000 rotations. Pulp was diluted to 1% by adding dilution water. DDA Test DDA (dynamic drainage analyser from Akribi Kemi Konsulter in Sweden) was used to measure retention and drainage. 500ml of pulp was used for each test point. Polyaluminium chloride (PAC, PAX-XL63) or Alum and pulp were added to a 500ml breaker with 100 rpm magnetic stirring for 10 minutes before drainage. Pulp was poured to DDA 30s before drainage and the DDA stirrer was adjusted Table 1. Chemical additions in DDA test for OCC furnish. Table 2. Chemical additions in DDA test for OCC + Kraft furnish. to 1000 rpm. Silica (FennoSil 422) and polymers were added before drainage and stirring was stopped 2 seconds before drainage. Vacuum was 300mBar for 30 seconds after drainage started. Wire opening was 0.25 mm. Drainage time was recorded and filtrate turbidity was measured immediately. Sheet from the wire was dried in a Lorenz & Wettre hot plate dryer to abs dry for retention calculation. The times of chemical additions in the DDA tests added to 8.5ml of water. 0.5ml of iodine reagent, with a consistency of 7.5 g/l KI + 5 g/l I2, was added and the absorbance value was measured at 610nm by a Hach Lange DR 900 spectrophotometer, 1 minute after iodine solution was added. Zeroing of the spectrophotometer was done with the sample before iodine addition. C x film 07311 non-ionic degraded starch was used as the reference to correctly calibrate the starch content. A blank test for HCl-iodine solution absorbance was made to subtract the baseline absorbance from the result. Starch retention was calculated as: (pulp starch - filtrate starch) / pulp starch x 100%. Hand Sheet Test 1 Thick stock consisting of 50% OCC and 50% kraft pulp was diluted to 1% consistency with clear filtrate and wire water in a 50:50 ratio. Both the process waters and the thick stock were from the same liner machine. The hand sheet machine was filled with conductivity and Calcium-adjusted water. The level of conductivity and Calcium was the same as in the clear filtrate. Basis weight in the Rapid Kötchen sheet former was 120 g/m2. Hand Sheet Test 2 Thick stock was diluted to 1% with conductivity and Calcium adjusted water. The level of conductivity was 4 mS/cm and Calcium was 520 mg/l Ca2+. The hand sheet machine was filled with conductivity and Calcium adjusted water. Circulation water hand sheets were made. 5 initial sheets were discarded in each test point. Basis weight in the Rapid Kötchen sheet former was 120 g/m2. Time,s Addition -600 PAC, (10 kg/t comm.) -15 Silica, (3 kg/t comm.) -10 Novel amphoteric polymer -10 Conventional CPAM 0 Drainage Time,s Addition -600 Alum (8kg/t) -40 Cationic starch (4 kg/t) -40 Surface size starch (40 kg/t) -30 Novel amphoteric polymer -20 Conventional CPAM -10 Bentonite (3,5 kg/t) 0 Drainage are shown in tables 1 and 2. Cationic starch used with OCC + Kraft furnish was Meribond 155. Surface size starch was C x film 07312, nonionic dextrinated starch. Determination of Soluble Starch from DDA Filtrate 25ml of filtrate was added into 10ml of 10%-w HCl. The Mixture was stirred for 10 minutes with a magnetic stirrer and filtrated by gravitation in a funnel containing black ribbon filter paper. 1ml of filtrated mixture was