A COMPARATIVE STUDY OF THE NUTRITIONAL QUALITY OF FRESHLY EXTRACTED JUICES FROM ORGANIC VERSUS CONVENTIONAL ORANGE AND APPLE FRUITS

ABSTRACT

Freshly extracted juices obtained from organically and conventionally produced orange and apple fruits were assayed in terms of their nutritional quality. Parameters used in the assessment were total soluble sugars, ascorbic acid content, folic acid concentration, acidity, glucose, fructose, maltose and sucrose contents, as well as the concentrations of sodium, potassium, calcium, iron, zinc and copper. Total and individual sugars were detected using HPLC while brix concentrations were measured through a hand-held optical refractometer. Enzyme immunoassay method was used for vitamin analysis while both flame photometer and AAS were used for the minerals. It was observed from this study that the total soluble solids of juices obtained from conventionally grown fruits are slightly higher than their organic counterparts. However, apple juices revealed more percent soluble solids (12.8 - 13.56 oBrix) than juices obtained from orange (10.78 – 11.6 oBrix) and this was higher for apple juices from conventional sources. The highest soluble sugar concentration detected was sucrose (4.21 – 5.66 g/100 mL) and conventional apple juices had the highest amount. Maltose was not detected in all the analysed samples and this may be due to the absence of starch and the enzyme, amylase. Glucose concentrations were reportedly slightly higher (2.83 – 3.11 g/100 mL) in conventionally grown fruits than their organic counterparts (2.59 - 2.79 g/100 mL). Both organic and conventional orange fruit juices were observed to contain higher amounts of potassium, sodium, calcium, copper and zinc than their counterparts from apple. Concentrations of ascorbic acid were highest (480 mg/ L) in organic orange juice and the lowest was detected in conventional apple juice (190 mg/ L). For folic acid, organic apple juice had the lowest amount (61.29 µg/ L) while juice from conventionally grown oranges contained the highest mean amount (84.23 µg/ L). Generally, the variations observed in the nutritional quality and chemical characteristics of some freshly squeezed juices (which was mostly significant when comparing juice from different fruit species) may be due to differences in species, variety, farming system adopted, environmental, soil and climatic conditions, time of harvesting, length of storage, extraction technique, storage conditions, incidence of diseases and pests as well as origin of fruits. More research on other nutritional aspects such as amino acid profile, antioxidant activity, phenolic and organic acid composition may be necessary in order to provide more information for better comparison.