Only need the discussion portion done. No word limit.
INTRODUCTION: What is nonenzymatic reaction? Types of it? What is Maillard reaction? How does it occur? The reaction that takes place? Occurs naturally? Can it be induced? Is it a desired process? No? ways to inhibit process? Nonenzymatic browning is a chemical reaction which occurs by several mechanisms that involve reactive sugars and amino compounds. It is found in food processing operations involving dehydration/concentration. The browning effect increases parallel to process pH and/or temperature – both of which yields the formation of complex “melanoidin” browning polymers. These may significantly impact on the colour, flavour and nutritive value of processed food product. The reaction of reducing sugars (e.g. glucose, fructose, lactose and maltose) with amino compounds (e.g. amines, amino acids, proteins) may result in browning also known as Maillard reaction. This reaction is not enzyme catalysed but is affected by various factors including temperature, concentration of reactants, pH, inhibitors and preservatives (Ajandouz and Puigserver, 1999). At increased temperatures, caramelisation occurs and subsequently pyrolysis (O'Brien and Morrissey, 1989). The various factors that influence the Maillard reaction (Ames, 1990) can be considered as food processing and storage variables. It includes the nature of the reactants (i.e. the composition of the raw materials), the temperature-time combination used during heating and storage, the pH and water activity of the food, the presence of oxygen and metals, and the presence of any reaction inhibitors, such as sulfur dioxide. The manipulation of these variables will affect the balance of the various chemical pathways that make up the Maillard reaction (Ames, 1998). Melanoidins are polymeric and coloured final product of Maillard reactions. They are responsible for physical properties such as colour and viscosity as well as organoleptic properties such as stabilising flavour substances present in cooked and processed foods (Reyes et al., 1982). These are a variety of pathways that form reactive intermediates that can yield volatile flavour components and brown melanoidins. The formation of these is desirable in some food items such as meat, bread and coffee. However, its occurrence during storage is undesirable and may lead to lower quality such as darkening of dehydrated fruits, eggs and vegetables. They have good binding properties towards low molecular weight substances in food matrix which may have an impact on food in terms of technology, nutrition and physiology. MATERIALS AND METHODS: A total of 9 pairs of test tubes were prepared according to Table 1. 2 pairs of tubes (A, B) contained 4mL invert sugar solution (50° Brix), 1mL distilled water (diH2O) and 1mL 50mM sodium phosphate pH 8.0. A pair of it was used as a blank solution (A) while the other was labelled as “No Glycine” solution (B). The blank tubes were set aside and incubated at room temperature. The remaining 7 pairs of tubes contained 4mL invert sugar solution (50° Brix) and 1mL 10% (w/v) glycine. Of the 7, 3 pairs (E, H, I) had the addition of 1mL 50mM sodium phosphate pH 8.0 while the remaining 4 pairs (C, D, F, G) had the addition of either 1mL 50mM sodium phosphate pH 6.0 or 7.0 or 1mL 50mM sodium carbonate pH 9.0 or 10.0. Of the 3 pairs that had the pH 8 solution added, a pair had an addition of 0.1g sodium metabisulfite (H) while another pair was incubated at 70°C (I). All tubes were covered with plastic lids and were incubated at 100°C except for the aforementioned. The tubes were incubated for 30 minutes, then cooled to room temperature in tap water. The tubes were then read for absorbance values on a spectrophotometer at 420nm using the blank solution to zero the machine. Table 1: Reagents added to each pair of test tubes. "Y" denotes that the reagent was added. Reagents A B C D E F G H I 4mL invert sugar solution (50° Brix) Y 1mL 10% (w/v) glycine Y 1mL distilled water (diH2O) Y 1mL 50mM sodium phosphate pH 6.0 Y 1mL 50mM sodium phosphate pH 7.0 Y 1mL 50mM sodium phosphate pH 8.0 Y Y Y 1mL 50mM sodium carbonate pH 9.0 Y 1mL 50mM sodium carbonate pH 10.0 Y 0.1g sodium metabisulfite Y RESULTS: The absorbance values for each pair was averaged out and the values were plotted in a graph against their corresponding factors. The effects of nonenzymatic browning were demonstrated using the model system presented. Figure 1 shows the effects that nonenzymatic browning has at different pH, temperature, with and without an amine group (glycine) as well as when an inhibitor (sodium metabisulfite) was added. (a) (b) Figure 1: Effects of nonenzymatic browning. (a) The effects of Maillard Reaction (mainly) at increasing pH values while being incubated at 100°C. (b) The effects of several factors on nonenzymatic browning while keeping a constant pH 8.0. DISCUSSION: REFERENCES: Food Science and Nutrition and the Maillard Reaction - Melanoidins [Online]. Available: http://www2.warwick.ac.uk/fac/med/research/biomedical/tem/mvhealth/proteindamage/food_nutrition/melanoidins/ [Accessed]. AJANDOUZ, E. H. & PUIGSERVER, A. 1999. Nonenzymatic browning reaction of essential amino acids: effect of pH on caramelization and Maillard reaction kinetics. J Agric Food Chem, 47, 1786-93. AMES, J. M. 1990. Control of the Maillard reaction in food systems. Trends in Food Science & Technology, 1, 150-154. AMES, J. M. 1998. Applications of the Maillard reaction in the food industry. Food Chemistry, 62, 431-439. O'BRIEN, J. & MORRISSEY, P. A. 1989. Nutritional and toxicological aspects of the Maillard browning reaction in foods. Crit Rev Food Sci Nutr, 28, 211-48. REYES, F. G. R., POOCHAROEN, B. & WROLSTAD, R. E. 1982. Maillard Browning Reaction of Sugar-Glycine Model Systems: Changes in Sugar Concentration, Color and Appearance. Journal of Food Science, 47, 1376-1377. Effects of Nonenzymatic Browning At 100°C6789100.131500000000000010.482500000000000040.840999999999999971.14950000000000021.6625000000000001No Glycine80.34899999999999998Sodium Metabisulfite81.4500000000000001E-2At 70°C80.20750000000000002pH Value Absorbance @ 420nm Factors Affecting Nonezymatic Browning @ pH 8.0 At 100°CNo GlycineSodium MetabisulfiteAt 70°C0.840999999999999970.348999999999999981.4500000000000001E-20.20750000000000002 Absorabance @ 420nm INTRODUCTION: PRAC 4: What are lipids? Types of lipids? Those that are found in food or used in food? Cooking oil derivatives? Like where they come from? Main source: plant or animal? Why is there difference? What is saponification value? Acid value? Density of oil? What do they represent? How to determine these values? What are the expected values? What is “reverse pipetting? Why used in density determination? Official AOAC methods for SV & AV. Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells. It includes fats, oils, waxes, certain vitamins, hormones and most of the non-protein membrane of cells. Lipids mainly have hydrocarbons in their composition and are highly reduced forms of carbon. When metabolised, lipids are oxidised to release large amounts of energy, making it useful to living organism. Fats and oils are composed of triacylglycerol or triglycerides. Complete hydrolysis of triacylglycerol yields three fatty acids (FA) and a glycerol molecule. FA are long chain carboxylic acids, which may or may not contain carbon-carbon double bonds. Oleic acid is the most abundant FA in nature. There are four types of FA: saturated, monounsaturated, polyunsaturated and trans. Saturated FA and trans fat are associated with an increased risk of coronary heart disease, while monounsaturated FA (MUFA) and polyunsaturated FA (PUFA) are associated with a decreased risk of heart disease (Wahrburg, 2004). Therefore, it is important to measure the fat content of food products to provide the necessary information for the customer and allow them to make decisions accordingly. In addition, Food Standards Australia New Zealand (FSANZ) regulates the amount of fats and saturated fats in a product to be displayed in the nutritional panel (FSANZ, 2015). Fats and oils are widely used in the world, coming from both animal and plant sources. There are different types of oil such as vegetable oil, extra virgin olive oil, peanut oil and rice bran oil. The different types of fats include butter, lard and margarine. When some food (i.e. oil and fat) is exposed to heat or moisture, they begin a process called lipolysis; which breakdowns lipids into glycerol and FA via hydrolysis of triglycerides (Lass et al., 2011). These FA are the ones responsible for unpleasant odours and flavours in some food, also known as rancidity. Therefore, it is important to measure the percentage of free fatty acids (FFA) to determine the quality of the product. FFA is used to determine of the oil or fat is rancid enough to be discarded by using the level of percentage FFA (%FFA) as oleic acid. The %FFA can be determined by titrating base potassium hydroxide (KOH) against sample. This combination will result in the neutralisation of carboxylic acids groups in the solution. The amount of FFA in the solution is proportional to the amount of base required to neutralise the solution, and this is indicated by a change of colour using phenolphthalein. Another quality test of oil based products is the saponification value (SV). Saponification is the process of breaking down or degrading a neutral fat into glycerol and FA by treatment of the fat with an alkali. The saponification is defined as the amount of alkali necessary to saponify a given quantity of fat or oil. It is expressed as mg of KOH required to saponify 1g of the sample. The SV is an index of the mean molecular weight of the triacylglycerol in the sample. The smaller the SV, the longer the average FA chain length. The calculated SV is determined from the fatty acid composition. METHODS AND MATERIALS: Part A: Saponification Value Approximately 2g of different types of cooking oil was weighed into individual 250mL round-bottom flask containing a few boiling chips. An aliquot (25mL) of 0.5M alcoholic potassium hydroxide (KOH) solution was added to the flask. The solution was boiled under reflux for 40 minutes, then cooled and 1mL of 1% phenolphthalein indicator was added. A blank was set up in a 250mL conical flask containing 25mL of 0.5M alcoholic KOH solution and 1mL of 1% phenolphthalein indicator. Both the sample and blank were titrated against 0.5M hydrochloric acid (HCl) until colourless. Part B: Determination of Oil Density A beaker was placed on an analytical balance and tared. Aliquots (200µL, 500µL and 1000µL) of peanut oil was pipetted using “reverse pipetting” technique and the weight of oil was recorded. For each aliquot, a minimum of 4 readings was obtained, taring the analytical balance between each reading. A calibration curve was plotted using the oil weight against the pipetted volume to obtain the density of oil. Part C: Acid Value Approximately 6g of different types of cooking oil was weighed into individual 250mL conical flask. In a second 250mL conical