Title:A: Non-enzymatic browning in food.B: Enzymatic browning in food.C: Protein Functionality.Introduction:A: The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat.
Like caramelization, it is a form of non-enzymatic browning. The reactive carbonyl group of the sugar interacts with the nucleophilic amino group of the amino acid, and interesting but poorly characterized odour and flavour molecules result. The brown pigments that form are called melanoidins. Unwanted brown colors and off- odors can develop during extended storage of foods as baked products, dried egg whites and instant mashed potatoes. The Maillard reaction known as nonenzymatic browning because enzymes are not part of the reaction and its can be viewed as a sequence of three chemical reactions such as condensation, rearrangement and polymerization.B: When foods like fruits and vegetables are cut or peeled, they release an enzyme from their cells, which is known as phenolase or polyphenol oxidase. This enzyme is highly reactive in the presence of oxygen.
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It catalyzes a biochemical reaction that converts the phenolic compounds present in foods to brown pigments known as melanins. This reaction is known as enzymatic oxidative browning, which renders food the typical black or brown tinge. These polyphenols are unstable and undergo oxidation when exposed to air through a series of biochemical reactions involving conversion of one substrate to a product.
The most common chemical reaction taking place is the catalysis of first step of biochemical reactions involving formation of quinones from phenolic compounds, and subsequent polymerization of quinones to insoluble polymers known as melanin. This compound called melanin is responsible for the browning of fruits and vegetables, especially apples which are rich in polyphenols and highly susceptible to enzymatic browning.C: Food protein functionality has classically been viewed from the perspective of how single molecules or protein ingredients function in solutions and form simple colloidal structures. Based on this approach, tests on protein solutions are used to produce values for solubility, thermal stability, gelation, emulsifying, foaming, fat binding and water binding to name a few. While this approach is beneficial in understanding the properties of specific proteins and ingredients, it is somewhat restricted in predicting performance in real foods where the complexities of ingredients and processing operations have a significant effect on the colloidal structures and therefore overall properties of the final food product. In addition, focusing on proteins as just biopolymers used to create food structures ignores the biological functions of proteins in the diet. These can be beneficial, as in providing amino acids for protein synthesis or bioactive peptides, or these can be detrimental, as in causing a food allergic response. This review will focus on integrating the colloidal/polymer and biological aspects of protein functionality.
This will be done using foams to illustrate colloidal/polymer aspects and bioactive peptides to demonstrate biological function.Objectives: A: To show the effects of non-enzymatic browning on different sugar mixtures.B: To show the effects of enzymatic browning on apples.C: The stability of Protein Foams – Measurement.Methods and Materials.A: As per lab manual. – NaOh/HCL was added. NaOH was added to rise the pH accordingly and HCL was added accordingly to lower the pH.
B: As per lab manualC: As per lab manual Results:A: Non-enzymatic browning in food. A of samples @ 60°C A of samples @ 40°C1 0.001 1 0.
0022 0.001 2 0.0693 0.095 3 0.8714 0.
000 4 0.0035 0.012 5 0.2206 0.005 6 0.0057 0.
001 7 0.001These absorbance results were read seven days after the solution were placed in the oven at 40°C and 60°C.B: Enzymatic browning in food.Undipped apple +++++ very severeDipped apple 1% citric acid +++ severe1% ascorbic acid ++ moderate1% EDTA + slight1% citric acid, 1% ascorbic acid + slightC: Protein Functionality. 10 min 20 min 30 min 40 min 50 min 60 min0.
38g cream of tarter 2ml 4ml 6.5ml 7.5ml 10ml 11.5ml12 drops of egg yolk 5ml 12.5ml 22.
5ml 30ml 37ml 44ml0.76g cream of tarter 8ml 20ml 23.5ml 27ml 30ml 35ml1.56g of salt 4ml 7ml 9.5ml 12ml 12.5ml 13.5ml30ml of water 5ml 8.
5ml 12.4ml 14.5ml 17.
5ml 19.5ml50g sucrose(soft peak) 0ml 0ml 0ml 0ml 0ml 1ml30g water + 50g sucrose 0ml 0ml 1.5ml 1.5ml 1.5ml 1.5mlTreatment 1 0ml 2.
5ml 6ml 9.5ml 11.5ml 13mlTreatment 2 14ml 15ml 16ml 17ml 18ml 18mlTreatment 3 0ml 0ml 0ml 0m 0ml 0mlDiscussion: A: Non-enzymatic browning in food.This experiment is conducted mostly in pH 8 buffer rather than a more typical food pH (3-7) because non-enzymatic browning reaction undergo particularly in alkaline solution. The Hydrolyzed protein browned slower than an intact protein because most of the chain of protein break and the amount of amino acid less than its origin so that the protein can’t brown faster as intact protein. In the 3rd sample the absorbance is much higher than the rest of the samples. This sample browned the fastest due to the fact it was the only sample where no water was added, and water is a browning inhibitor.
It was also observed that the 4th sample has the lowest absorbance, this may be because there was more glucose and no glycine added to this sample which may cause browning to be prohibited. It was also evident that the samples browned faster at 40°C B: Enzymatic browning:In this experiment it was expected that the dipped samples were going to be much less brown that the undipped apple samples. This is due to the fact that the sample that have been dipped with acid which prohibits enzyme browning. The apples that were undipped were much browner as they has no browning inhibiting characteristics. This is evident in the results obtained above. The principal of this experiment is the level of browning can be severely reduced or even inhibited by the use of samples used in this experiment epically acid. Also the following will prevent enzymatic browning:– Reduce/prevent tissue damage–Reduce contact with air (e.
g., immerse)–Inhibit PPO–Include antioxidants–Heat inactivate PPOC: Protein functionality: In foam formation three stages are involved. First, the soluble globular proteins diffuse to the air/water interface, concentrate and reduce surface tension. Second, proteins unfold at the interface with orientation of polar moieties toward the water; as a result of unfolding, there is orientation of hydrophilic and hydrophobic groups at the aqueous and non-aqueous phases.
Third, polypeptides interact to form the film with possible partial denaturation and coagulation. Proteins rapidly adsorb at the interface and form a stabilizing film around bubbles which promote foam formation. The basic function of proteins in foams is to decrease interfacial tension, to increase viscous and elastic properties of the liquid phase and to form strong films. Protein foamability is correlated with its capacity to decrease surface tension at the air-liquid interface. Proteins possess the ability to absorb at the interface and reduce surface tension. Surface tension at the gas-liquid interface is affected by temperature; the higher the temperature, the lower the surface tension due to changes in protein conformation.
The surface tensions of soybean protein and egg albumin were low and close to hemoglobin, but the foaming power of hemoglobin was considerably higher. Casein had a higher surface tension than lysozyme, but the foaming power of casein was significantly higher than lysozyme. Surface tensions of the protein solutions changed with time. This can be seen from the results above. In the sample with 50g of sucrose is produced the least amount liquid at the bottom whereas the 12 drops of egg yolk sample produced the most amount of liquid as there was very little amount of foam produced.Conclusion:A: This experiment showed that food stuff can turn a brown colour without enzymes reacting and just by heat treatment of sugars and that water acts as a browning inhibitor ad different temperatures has an effect on the browning.
B: This experiment showed that acid acts as a strong browning inhibitor.C: Quality of protein foaming agents characterised by the volume of foam which can be formed during whipping and the stability of the foam once it has been formed.References: 1.Name of the author(s)2.Year published3.Title4.City published5.
Publisher1) ScienceStruck. (2018). Enzymatic Browning. online Available at: https://sciencestruck.com/enzymatic-browning.
2) E. Allen Foegeding.(December 2011, Pages 1853-1864). Food protein functionality: A comprehensive approach.
3) (2018). Enzymatic Browning of Apples. online Available at: https://studymoose.com/enzymatic-browning-of-apples-essay