Abstract:
Carrot juice has high nutritional and medicinal value, it helps disorders such as night blindness, acidosis, acne, they have high concentration of beta carotene (provitamin A) as well as vitamins B1 and C, Potassium and calcium. Fresh carrot juice has perishable nature and very limited shelf life. Quality deterioration of fresh carrot juice was investigated at different temperatures (15°C, 25°C and 37°C) using different pretreatment methods. The extracted carrot juice samples were divided into four, sample A was not treated (it also serves as the control) sample B was pasteurized, at 60oC for 5 minutes, sodium benzoate and sodium metabisulphite preservatives were added to sample C and sample D was pasteurized, sodium benzoate and sodium metabisulphite preservatives were also added to it. The total viable bacteria count and the total mould and yeast increased significantly during storage at 37oC, there was more microbial growth during storage at 37oC compared to other temperatures (15oC, 25oC) and low microbial growth during storage at 15oC. The brix level, total carotenoids, ascorbic acid, titratable acidity, specific gravity decreased significantly during storage, the viscosity and pH also increased during storage. The brix level decreased when temperature was increased. The samples with preservatives (NaC7H5O2 +Na2S2O5) were able to retain their brix levels compared to other samples without preservatives. The concentration of total carotenoids and ascorbic acid decreased significantly when the temperature was increased. The specific gravity decreased with increased temperature. It was observed that there was a significant increase in viscosity when the carrot juice is stored at 15oC and a less significant increase when the carrot juice is stored at 37oC, the viscosity reduces when the rotor speed (rpm) is increased. It was observed that carrot juices are pseudoplastic in nature during storage because the flow curve has a slope decreasing with increasing rate of shear.
The optimum storage period for carrot juice is eight (8) days at 15oC when it is pasteurized and preservatives (NaC7H5O2 +Na2S2O5) were added.
