Page 1 of 15 Semester Two 2020 Exam Faculty of Science UNIT CODE: CHM2962 TITLE OF PAPER: Food Chemistry PRACTICE EXAM TEST DURATION: 130 minutes (10 minutes reading + 120 minutes writing) and additionally 20 minutes for uploading answers The Plagiarism-Collusion declaration below must be digitally signed and uploaded with your submission. Submit your answers through the Moodle drop-box as a single pdf file. If you encounter difficulties then; Primary Emergency upload: Single pdf file via email to chm2962.clayton-x@monash.edu Secondary Emergency upload: via phone: +61 429303937 Malaysia Campus student emergency upload: Single pdf file via email to siow.lee.fong@monash.edu You can either TYPE your answers in the spaces provided directly in this question booklet OR answer them by HAND on paper. If typing into the question booklet, additional space will be created in the word document if needed. Don’t worry about the pagination of the final document. SAVE OFTEN! Drawings of structures will need to be scanned/ photographed with your phone and then inserted at the correct position within the document. If handwriting your answers then each page must be legible and clearly labelled with your name and student ID. Question numbers must also be clearly labelled and page numbers noted at the bottom of the page. AUTHORISED MATERIALS OPEN BOOK YES CALCULATORS YES SPECIFICALLY PERMITTED ITEMS YES if yes, items permitted are: No restrictions Candidates must complete this section if you are typing your answers in this question booklet STUDENT ID AND/OR NAME: THIS PAPER IS MARKED OUT OF A TOTAL OF 120 MARKS Answer ALL 12 Questions. Declaration: I have read and understood the University’s Student Academic Integrity Policy and Procedures, and I have abided by the Monash University Policy on Plagiarism and Collusion when completing this exam. Signed: Date: By typing your name in the line above, this will be taken as your signature of approval for the declaration If you are handwriting your answers then you must write out the declaration and sign it on your first page. Page 2 of 15 1“` 18 P E R I O D I C T A B L E O F T H E E L E M E N T S 1 H Hydrogen 1.008 2 13 14 15 16 17 2 He Helium 4.003 3 Li Lithium 6.941 4 Be Beryllium 9.012 5 B Boron 10.81 6 C Carbon 12.01 7 N Nitrogen 14.01 8 O Oxygen 16.00 9 F Fluorine 19.00 10 Ne Neon 20.18 11 Na Sodium 22.99 12 Mg Magnesium 24.13 3 4 5 6 7 8 9 10 11 12 13 Al Aluminium 26.96 14 Si Silicon 28.09 15 P Phosphorus 30.97 16 S Sulfur 32.06 17 Cl Chlorine 35.45 18 Ar Argon 39.95 19 K Potassium 39.10 20 Ca Calcium 40.08 21 Sc Scandium 44.96 22 Ti Titanium 47.90 23 V Vanadium 50.94 24 Cr Chromium 52.00 25 Mn Manganese 54.94 26 Fe Iron 55.85 27 Co Cobalt 58.93 28 Ni Nickel 58.70 29 Cu Copper 63.55 30 Zn Zinc 65.38 31 Ga Gallium 69.72 32 Ge Germanium 72.59 33 As Arsenic 74.92 34 Se Selenium 78.96 35 Br Bromine 79.90 36 Kr Krypton 83.80 37 Rb Rubidium 85.47 38 Sr Strontium 87.62 39 Y Yttrium 88.91 40 Zr Zirconium 91.22 41 Nb Niobium 92.91 42 Mo Molybdenum 95.94 43 Tc Technetium (97) 44 Ru Ruthenium 101.1 45 Rh Rhodium 102.9 46 Pd Palladium 106.4 47 Ag Silver 107.9 48 Cd Cadmium 112.4 49 In Indium 114.8 50 Sn Tin 118.7 51 Sb Antimony 121.8 52 Te Tellurium 127.6 53 I Iodine 126.9 54 Xe Xenon 131.3 55 Cs Cesium 132.9 56 Ba Barium 137.3 571 La Lanthanium 138.9 72 Hf Hafnium 176.5 73 Ta Tantalum 180.9 74 W Tungsten 183.9 75 Re Rhenium 186.2 76 Os Osmium 190.2 77 Ir Iridium 192.2 78 Pt Platinum 195.1 79 Au Gold 197.0 80 Hg Mercury 200.6 81 Tl Thallium 204.4 82 Pb Lead 207.2 83 Bi Bismuth 209.0 84 Po Polonium (209) 85 At Astatine (210) 86 Rn Radon (222) 87 Fr Francium (223) 88 Ra Radium 226.0 892 Ac Actinium (227) 104 (261) 105 (262) 106 (263) 58 Ce Cerium 140.1 59 Pr Praeseodymium 140.9 60 Nd Neodymium 144.2 61 Pm Promethium (145) 62 Sm Samarium 150.4 63 Eu Europium 152.0 64 Gd Gadolinium 157.3 65 Tb Terbium 158.9 66 Dy Dysprosium 162.5 67 Ho Holmium 164.9 68 Er Erbium 167.3 69 Tm Thulium 168.9 70 Yb Ytterbium 173.0 71 Lu Lutecium 175.0 90 Th Thorium 232.0 91 Pa Protoactinium 231.0 92 U Uranium 238.0 93 Np Neptunium 237.0 94 Pu Plutonium (244) 95 Am Americium (243) 96 Cm Curium (247) 97 Bk Berkelium (247) 98 Cf Californium (251 99 Es Einsteinium (254) 100 Fm Fermium (257) 101 Md Mendelevium (258) 102 No Nobelium (255) 103 Lr Lawrencium (260) Page 3 of 15 Question 1 (1+1+1+1+1+1+1+1+1+1 = 10 marks) For answering Question 1, either circle your chosen answer and submit the pages, or write the corresponding number on your answer page and submit. a) Carvone is found in many essential oils. The form of carvone in spearmint leaves smells of spearmint and the form of carvone in caraway seeds smells of caraway. The reason for these different properties is: a) they are diastereomers and hence smell different. b) they are enantiomers that have different physical and chemical properties in an achiral environment c) they are constitutional isomers d) they are enantiomers that have different physical and chemical properties in a chiral environment. b) Which of the following is a polyunsaturated fatty acid: a. Sapienic acid b. Palmitic acid c. Linoleic acid d. Elaidic acid c) Which of the following is NOT an amino acid: a. aniline b. lysine c. glycine d. threonine d) Which of the following is NOT a micro-mineral a. Zinc b. Copper c. Iodine d. Bromine e) The initial gelatinization temperature of starch lies in the range 55–70°C. Which of the following techniques can be used to determine gelatinization temperature Circle all correct answers. I Brabender amylograph II Differential scanning calorimetry (DSC) III Viscometer IV Polarized microscope f) The units for molar absorptivity are: a) L/cm Mol b) cm Mol/L c) Mol/L cm d) Unitless g) Which of the following structures are: dioxin and, the closely-related poly-chlorinated biphenyl and dibenzofurans Page 4 of 15 a) II, IV b) II, III, IV c) I, IV d) III, IV h) Which of the following are a carbohydrate-derived functional ingredient I Taurine II Anthocyanin III Chitin IV Flavonones V Capsaicinoids a) V, IV b) II, I c) III, V d) III e) II, IV i) Identify 2 applications from the following where pectin is used to control the functional properties of foods: A. Thickening and gelation of fruit pulp B. Preventing starch retrogradation C. Water binding D. Stabilisation of emulsions in meat products E. Stabilisation of ice cream j) Apart from the textural transitions for food ingredients as the water activity increases, what are some additional effects of increasing aw a) The viscosity decreases. b) The rate of microbial regrowth and enzymatic reactions increase. c) The water content decreases as the aw increases d) The mobility of reactive species decreases as the aw increases. Page 5 of 15 Question 2 (4+3+3 = 10 marks) a) Give the generic names for 4 different classes of saccharides (ie, carbohydrates) and explain the basis of this classification. (4 marks) b) The following structures are the four stereoisomers of glucose. Assign D- and L- stereoisomers to each structure. (3 marks) c) Name 3 oligosaccharides present in legumes (e.g. peas, beans, soy-beans) and the number of sugars in each. (3 marks) Page 6 of 15 Question 3 (3+3+2+2 = 10 marks) a) Briefly describe three structural differences between oleic and arachidonic acids. (3 marks) b) Draw the following polyunsaturated fatty acid: cis,cis,cis-18:3 (n-6) (3 marks) c) Why are long chain fatty acids generally insoluble in water (2 marks) d) The most appropriate temperature range for frying food is in the range of 180 to 190°C. Give one detrimental effect when food is fried below 165°C and one detrimental effect when food is fried above 195°C. (2 marks) Page 7 of 15 Question 4 (2+4+2+2 = 10 marks) a) What is the important factor that determines how a polypeptide chain folds to form higher order structures of a protein, ie, secondary, tertiary and quaternary structures What is the ‘native’ structure of a protein and is this structure consistent for a given protein (2 marks) b) Protein denaturation can occur under various circumstances/conditions. What is necessary to disrupt (i) disulfide and (ii) salt/ionic bridges. (4 marks) c) State whether the following statement is TRUE or FALSE and explain your answer: “All proteins are enzymes” (2 marks) d) What is the function of kappa-casein proteins and colloidal calcium phosphates in the formation of casein micelle structures (2 marks) Page 8 of 15 Question 5 (2+1+2+3+1+1 = 10 marks) a) Name two vitamins that have anti-oxidant properties. Which one might be used in a margarine spread and why (2 marks) (1 marks) b) Write a brief summary of the synthetic pathway of stilbenes from phenylalanine focusing on the structural steps with respect to numbers of carbon atoms. Note that structures are not needed. (2 marks) c) What are flavonoids and what foods are they found in Name 3 sub-classes of flavonoids (3 marks) d) What is the chemical difference between chitin and chitosan and what is the chemical process to produce chitosan (1 mark) (1 mark) Page 9 of 15 Question 6 (4 + 2 + 1 + 3 = 10 marks) a) Below is shown the UV-visible absorbance spectrum of a common food dye. (i) What colour(s) of light is it absorbing (ii) What colour do you expect a solution of this dye to appear (iii) On the diagram, above or drawn on paper, draw the UV-visible absorbance spectrum of patent blue V. (1 + 1 + 2 marks = 4 marks) b) Table salt (sodium chloride) contains magnesium silicate. Why is this added (2 marks) c) Why is monosodium glutamate added to food (1 mark) d) Capsaicin, structure below, is an active components of chili peppers. Explain why drinking milk helps to alleviate the burning sensation on the tongue that occurs when eating chillies, but water does not. O NH O OH (3 mark) Page 10 of 15 Question 7 (4 + 6 = 10 marks) a) As an analytical chemist you have been tasked with analysing for pesticide residue in a cereal product. Describe your initial screening method and then the quantitative method used to identify and determine the concentration of a known pesticide within the cereal sample. (4 marks) b) The following molecules are ‘functional’ additives to food products or are potential contaminants. Ethylenediaminetetraacetic acid (EDTA) Sulfur dioxide 1,1-(2,2,2- Trichloroethylidene)bis(4 -chlorobenzene) Malathion Sodium benzoate Pirimicarb i) Which ones are ‘functional’ additives ii) Which ones are potential contaminants iii) Butylated hydroxytoluene (BHT) is an anti-oxidant. Describe how it prevents the rancidification of food. iv) Name another food-compatible anti-oxidant that that preserves by its direct reaction with oxygen (1 + 1 + 2 + 1 = 6 marks) Page 11 of 15 Question 8 (2+1+2+3+2 = 10 marks) a) Give two functional roles of pectin in jelly beans. (2 marks) b）What is the functional role of carrageenan when used in low-fat margarine (1 mark) c) Explain why solid fats are usually opaque compared to liquid oil (2 marks) d) Give 3 factors that affect opacity of solid fats. (3 marks) e) Differentiate between foaming capacity and foaming stability. (2 marks) Page 12 of 15 Question 9 (2 + 2+ 2 + 4 = 10 marks) a) Briefly explain how can Zeta potential measurements be used to determine the stability of a colloidal system. (2 marks) b) Below is the structure of lecithin. On this structure circle AND label the following; (i) The glycerol backbone (ii) The unsaturated fatty acid chain (iii) The saturated fatty acid chain (iv) The two most polar groups (2 marks) c) Calculate the Laplace pressure ( P) is P = 2γ/R for the following; 15 μm radius oil droplet with interfacial tension of 10 mN/m (2 marks) d) Given the following information describe which food product you would add the following emulsifiers. Explain your reasons. i) Sodium lauryl sulfate, HLB ~40 ii) Sorbitan monostearate, HLB ~4.7 (4 marks) Page 13 of 15 Question 10 (1 + 4 = 10 marks) a) The Karl-Fisher titration method has been widely used to determine water content of food. Write the reaction and explain the principle of this method. (3 marks) b) Supercritical carbon dioxide is used to extract some food components. Briefly explain what supercritical carbon dioxide is and give an example of its use in the food industry. (3 marks) c) Give two ways in which the properties of bound water differ from those of free water. (2 marks) d) Is water activity the same as water content Briefly explain. (2 marks) Page 14 of 15 Question 11 (2+1+2+1+2+2 = 10 marks) a) Name 2 common preservatives that are allowed in fruit juices and their specific function (2 marks) b) What is the chemical class responsible for the red colour of wine and whose colour varies as a function of pH (1 mark) c) Which chemicals give rise to the colour in the following foods i) carrots ii) ripe tomatoes (2 marks) d) What is the function of the cobalt sulphate when used as an additive in beer (1 marks) e) What are two key types of flavours in beer and their origin (2 marks) f) What are the major defects in Irish Cream Liqueur that can occur during their on-shelf life (2 marks) Page 15 of 15 Question 12 (1+1+1+1+4+2 = 10 marks) a) What is the compound that is responsible for the red colour of meat (1 mark) b) The majority of soluble iron in meat is in myoglobin. List the other types of soluble iron in meat. (1 mark) c) Explain why the colour of fresh meat changes when it is cut and exposed to air (1 mark) d) During cooking meat changes colour again. Briefly explain the chemistry behind this colour change. (1 mark) e) In the bread-making process, the following steps occur. Write down the chemical changes that accompany each step: i) water is added to flour ii) the dough is kneaded iii) proofing iv) baking (4 marks) f) Explain the chemistry behind the development of the pleasant aromas, colour and texture of baked bread (2 marks) END OF PAPER
