ABSTRACT

Three Fruits, orange (Citrus sinensisa), pawpaw (Carica papaya) and tomato (Lycopercium esculentum) were obtained, cleaned, washed, cored (or deseeded) and separately crushed into pulp. A hundred ml of pulp were then treated with alum at 0.25g, 0.5g, ig; enzyme extract (pectinase) at 5 ml, l0ml and 15 ml or electric current at 220V for 5, 10, and 15 mm. respectively. Two hundred ml of the three pulps were in another instance electrically heated at 9V DC or ohmic heated at IIOV ac using Copper/Aluminum (CU/AL) or Copper/Copper (CU/CU) as electrodes for 5, 10 and 15 mm. respectively. Five hundred ml of each of the fruits pulp were also separately treated with sugar, alum and NaCI at concentration of 0.5, 1.0, 1.5 and 2.Og respectively, kept for 20 mm, and then ohmic heated at 11 OV for 10 mm. Another 500 ml of each pulp were ohmic heated for 10 mm at various voltages of 60, 80, 90, 100 and 11 OV. After each treatment, juices were pressed out from the puips under a constant pressure through a muslin cloth on a Buckner funnel. The juices obtained were measured for yield, soluble solid, viscosity, pH, color and ascorbic acid. The temperature distribution in the ohmic apparatus was monitored. Tomato juice samples were inoculated with Listeria monocytogen, E.coil Salmonella spp. and Clostridium weichi, then ohmic heated for 5, 10, 15 and 20 mm. at 70 or 100°C, and the pathogen destruction monitored. The result indicated increase in yield with the use of enzyme, alum and electric current at 220V, where enzyme gave the highest yield and electric current the least. The use of different electrodes at voltages of 9V and 110V significantly (P<0.05) increased yields: The 1IOV CU/AL treated samples gave the highest yield but 1.IOV CU/AL samples showed a better juice quality (Colour, Vitamin C. pH). The addition of alum, sugar and NaCI further improved yield and enhanced stability of ascorbic acid (AA) and colour of the juices. The linear regression conducted showed that . for every voltage increase tomato juice increased by 1.18 ml, orange - 0.5 ml and papaya —0.76 ml; tomato increased by 90 ml, while orange increased by 46 ml with 25 NaCI per 500 ml of pulps but papaya increased by 14.7 ml at o.5 g NaCI and  decreased as concentration of NaCI increased. The addition of sugar improved rn papaya yield by 52 ml, while alum by 42 ml at 2g / 500 ml of pulp. The viscosity of the juices increased as the solid matter increased with orange the most viscous. Temperature, heating time, voltage, electrode type and additive type affected the AA retention. For every 1.0g. of additive, orange retained 5.7% AA, tomato 10.12%, while papaya retained 4.27%. However, for every minute of heating, degradation was 4.5% for orange, 5.2% tomato, and 56% for papaya; for each voltage increase, orange decreased it's AA by 0.36%, tomato 0.41% and papaya 1 .3%. The pH of the juices varied per treatment but increased with ohñiic heating. It was also found, during microbial analysis, that ohmic heating was highly effective in pasteurization and even sterilization at longer heating time of 20 mm. This work proved that ohmic heating, electrode type, addition of additive, increased juice yield, aided, retention of (AA) in juices and further destroyed pathogens of commercial importance.