Practical 1: Evaluation of Properties of Foods 1A) pHObjective:To determine the pH value of orange juice.Introduction:pH is a measure of the acidity or basicity of an aqueous solution. pH is an important aspect that is being inspected in food processing and food preservation. pH control method is one of the method used by food manufacturers to prevent growth of microorganisms in food that will eventually cause early food spoilage and food contamination. Most foodborne pathogens cannot grow below pH 4.4 (Montville, Matthews & Kneil, 2012). Most microorganisms grow best in the pH range of 6.5 to 7.5 (Ministry of Agriculture, Food and Rural Affairs of Ontario 2013). Hence, pH level of food ...view middle of the document...
The typical pH values of fruit juices must be less than 4.5 (Montville, Matthews & Kneil, 2012). The study of US Food and Drug Administration (U.S. Food and Drug Administration 2011) recorded that the pH range of orange juice varies within 3.30 to 4.19. Thus, the recorded average pH of 3.56 in the sample of orange juice which fall in the established range is accurate and comparable with the data. Results show that orange juice has the lowest pH value (3.56) while milk has the highest pH value (6.83). The pH of orange juice and apple juice denote that both the sample is acidic. In contrast, milk with pH 6.83 is just slightly acidic. Low pH is required in both fruit juices to prevent microbial growth and contaminations in the products. This is because most foodborne pathogen cannot grow in pH medium that is below pH 4.4 (Montville, Matthews & Kneil, 2012). On the other hand, milk with slightly acidic properties records a pH that is nearly neutral because it can behave as a buffer solution. Milk contains a large number of substances such as lactic acid, citric acid and phosphate acid which act as weak acid or weak base. The presence of salts such as lactates, citrates and phosphates in milk also contribute to its buffer characteristic. Thus, milk has a higher pH compared to apple juice and orange juice.Conclusion:The pH of orange juice is 3.56. Orange juice has the lowest pH value and is the most acidic compared to apple juice and milk.B) Refractometery (Brix and Refractive index)Objective:To determine the degree of Brix and refractive index of marmalade.Introduction:Brix is the sugar contents of an aqueous solution. Refractive index measures liquid concentration and density. It is also used to monitor changes in soluble solids concentration of a solution. Refractometer is the instrument that is used to measure degree of Brix and refractive index in a food sample. Both Brix and refractive index are incorporated in quality control of food industry. Brix and refractive index measurement are crucial especially in sugar rich products like fruit juices and drinks. These products contain various sugars like glucose, fructose and sucrose as well as water. Various acids such as citric acid, malic acid and polymer sugar will also affect the refractive index. Food manufacturers have to make sure consistency in performance of the products, from batch to batch and season to season to meet the quality targets of product. As a result, processing in sugar rich products like beverages is carried out in the correct manner using fruits of an optimum level of maturity. However, the quality, maturity and sweetness of fruits are impossibly similar for every seasons and batches. But, with Brix and refractive index scale, the concentration of soluble solids in fruits can be determined. This theory has been applied in the wine making...