Citrus Juice Lab Report

The freshly squeezed citrus juices of Lemon,lime and orange were analysed through titration over the period of 2 weeks. Initially the lime juice was found to be slightly more acidic than the other juices followed by lemon juice and then orange juice since it is known that usually lime is more acidic than lemon and orange. It was hypothesised that the acidity of each juice will increase or decrease after the period of two weeks depending upon the sugar content of that citrus fruit that the juice is extracted from. The acidity of the juice with the highest sugar level will gradually increase over the period of time since sugar contribute to the the fermentation of the citrus juice to lactic acid. The hypothesis was shown to be correct;however

Lactic acid have more growth requirements than then normal bacteria since it was evolved in nutrient-rich environments. Lactic acid bacteria have diverse mechanisms for creating the energy needed to support and sustain biological activities. The availability of organic acid in the fruit can be important in allowing growth and metabolism. As lactic acid bacteria have the ability to produce large amount of acids, they often inhibit the development of other bacteria in juices and are able to cause their own autolysis. Excessive clarification and pre treatment of the fruit during the process of sending the fruit to the market which removes many of the natural yeasts and flora. The chemical compsition of juice also affect the rate of fermentation. Fruits generally tend to contain sufficient substrate (soluble sugars)that allow for the yeast and bacteria to fermented , so it can be said that because the fruits used did not show a very high increase in acidity it did not provide a sufficient substrate for the lactic acid bacteria that is present on the fruit to be used for fermentation.Temperature has an impact on the growth and activity of different strains of yeast. At temperatures of

Despite straining the lemon juice before titration, small amounts of pulp would have affected the titrations, because pulps was in some cases blocking the pipette when the juice is transformed from volumetric to conical flask. For future investigation, instead of straining the lemon juice, it could have been filtered to remove all pulp and thus increase the accuracy of the result vi. One possible improvement could have been to add an extra part to the investigation, involving the formation of a calcium citrate precipitate from the citric acid in the lemon juice (using limewater of a known molarity), which could be extracted and weighed: vii. This would allow the determination of the percentage of citric acid in the lemon juice specifically, rather than the total acidity. The results of this could have been compared to those of the titration, and the contribution of citric acid to the overall initial acidity could have been determined. viii. The experiment could have been performed over one a longer period of time day (rather than 14 days), which would have greatly reduced any loss of water from the sodium hydroxide solution, which may have improved results slightly. ix. citric acid increases the acidity of foods and makes it harder for bacteria to