Food Chemistry Practical Works 2023 PDF

Química e Estrutura dos Alimentos CRONOGRAM: Practical classes Presentation of the practical works TP1. Study of the alteration of proteins. A - Determin...

Química e Estrutura dos Alimentos CRONOGRAM: Practical classes Presentation of the practical works TP1. Study of the alteration of proteins. A - Determination of total basic volatile Nitrogen. B – cadaverin test TP2. Determination of total Nitrogen by Kjeldahl method. TP3. Foaming properties of proteins TP4. Fruit-based product analysis by refractometry TP5. Red-beet gelly based Evaluation test Rui Morais QEA 1 1 Cronograma/ Schedule Class Bioengineering+CNut B 26/0 03/ 10/ 17/ 19/09 24/10 23/11 9 10 10 10 Group TP4- Present. TP1 TP2 TP3 ---- test 1 5 Group TP4- Present. TP2 ---- TP1 TP3 test 2 5 Group TP4- Present. TP3 ---- TP1 TP2 test 3 5 Group Present. TP4-5 TP1 TP2 ---- TP3 test 4 Group TP4- Present. TP1 TP2 TP3 ---- test 5 5 Group TP4- Present. TP2 ---- TP3 TP1 test 6 5 Class A Nutritional Sciences 28/0 04/ 12/ 26/ 19/09 18/10 23/11 9 10 10 10 Group Present. TP1 TP2 TP3 TP4-5 ---- test 1 Group TP4- Present. TP2 ---- TP1 TP3 test 2 5 Group TP4- Present. TP3 ---- TP1 TP2 test 3 5 Group Present. TP4-5 TP1 TP2 ---- TP3 test 4 Group TP4- Present. TP1 TP2 TP3 ---- test 5 5 Group TP4- Present. TP2 ---- TP3 TP1 test 6 5 Rui Morais QEA 2 2 1 Química e Estrutura dos Alimentos TP 1: Study of the alteration of proteins. A - Determination of total basic volatile nitrogen. B – cadaverin test Fundament: Proteic Volatile amines(TMA, Nitrogen Volatile N Total DMA) Nitrogen: Ammonia Non-Proteins Urea Nitrogen Non-volatile N Creatinine q The freshness / degradation protein product (fish, meat) = fn content in: TBV-N, TMA. TBV-N↑ ou TMA ↑ : Deterioration degree↑ Rui Morais QEA 3 3 1. How is the TBV-N formed? q A.A. Ammonia q TMA-O TMA (non-volatile) (volatile) (Typical deteriorated odor) TBV-N combines measurement: - TMA (produced by bacterial action: Marine and intestinal flora) - DMA (produced by autolytic enzymes during freezing) - Ammonia (produced by deamination of AA and nucleotide catabolites) - Other volatile nitrogen compounds associated with the deterioration. 2. Test for CADAVERINE. How is it formed? LYSINE (A.A.) CADAVERINE (amine) - Descarboxylation reaction : > of microbial species associated with putrefaction. - Constitutes an additional assessment criterion of the state of putrefaction. Rui Morais QEA 4 4 2 Química e Estrutura dos Alimentos 1. Procedure: Sample + H2O Triturar 3 drops of silicone (anti-foam) K4[Fe(CN)6]: R. de Berthelot K4[Fe(CN)6] Zn(CH3COO)2: Avoid R. with Zn(CH3COO)2 metallic cations Phenolftalein (rosa-colorless) Li2CO3 Distilation Glass bids TBV-N. displaced H3BO3 by Li2CO3 (weak base) Tashiro Indicator (green-violet) Exp.: NH3: Titration with H2SO4 H2SO4 0.1M 2. Cadaverine test: + Ninhydrine (decarboxylation) + HEAT Extraction of the amines CHCl3 Notice the colour Rui Morais QEA 5 5 Calculation: Recolha do NH3 em frasco com H3BO3 Titulação em H2SO4 ü % TVB-N (mg NH3 /100 g amostra) Where: n(NH3) = 2x n(H2SO4) = V mL(H2SO4)x10-3 [H2SO4] M(NH3) = 17.0304 g/mol M(NH3) g = number moles NH3 x MM (NH3) X mg (NH3) is present in Y g sample Z mg (NH3) /100g product [H2SO4] = 0.1 moL/L (confirm the exact value) Rui Morais QEA 6 6 3 Química e Estrutura dos Alimentos TP 2: Determination of total nitrogen by Kjeldahl method Fundamental: Proteic Nitrogen Total Nitrogen: Non-proteic Nitrogen(NPN) Determination of Protein composition relating to the composition of organic N: % Protein = % Nitrogen x CONSTANT CONSTANT = fn (A.A. composition of the sample proteins): Constant: Source: 6.38 Milk and derivatives 6.25 Corn 5.95 Rice 5.70 Wheat 5.40 Pea flour Sample: Powder milk. q LIMITATION OF THE METHOD: qDetermines not only N protein but the total N, proteins, free AA, biogenic amines, purines, amides, alkaloids, etc. Rui Morais QEA 7 7 Procedure: Sample + H2SO4 + Catalist (Se) + CALOR Digestion Catalises the reduction of organic to NH4+ Distilation Add water + H2O + Phenolftalein (pink-colourless) Alkalinization (neutralise H2SO4) + NaOH (excess; displace NH4+) Distilation H3BO3 NH3 displaced Tashiro Indicator (green-violet) Recover of NH3 with boric acid H3BO3 Titrition with HCl HCl 0.1M Rui Morais QEA 8 8 4 Química e Estrutura dos Alimentos Calculations: Recover of NH3 in flask with H3BO3 Titration with HCl ü % Nitrogen: [HCl] = 0.1 moL/L (confirm the exact value) Where: n(NH3) = n(N) = n(HCl) = VHCl x 10-3 MHCl M(N) = 14.0067 g/mol M (N) g = number moles N (g) x MM (N) (g) X g (N) is present in Y g sample Z g (N) /100g product ü % Protein: Conversion factor for milk: 6.38 or 5.40 % Protein = % Nitrogen x 6.38 or 5.40 Rui Morais QEA 9 9 TP 3: FOUMING PROPERTIES OF PROTEINS Fundamental: Determination of the capacity and foaming stability of food protein solutions. Foam = Dispersion of a gas in a liquid or semi-solid. Proteins are located in the gas-liquid interface of the foam: Interfacial tension↓ : vCOALESCENCE ↓ Proteins: Emulsifing properties. Emultion ≠ Foam. q Foaming capacity= fn (pH, pI, [ ], T, Agitation, Matrix, …) q Stability of a foam= fn (Viscosity ↑, Interfacial tension↓, Proteic film – elasticity and resistency ↑, …) q Ex: Soufflés, Merengues, Ice cream, cakes, beer foam, etc Rui Morais QEA 10 10 5 Química e Estrutura dos Alimentos Rui Morais QEA 11 11 Schematic representation of a foam Ø: Vt = Total dispersion volume Vr = Vol. of the residual liquid Vi = Initial Vol. of protein solution Ve = Foam Volume = (Vt – Vr) Calculation: ü Foaming capacity of Proteins: ü Foam stability t ½ = Time at which the Ve = HALF of its initial value ln Ve = fn (t) Commenting on the results obtained referring to the influence of pH and concentration. Rui Morais QEA 12 12 6 Química e Estrutura dos Alimentos Procedure: Factors to consider: v pH v [Proteíns] v Type of agitation v Matrix: Sodium caseinate & Egg Sample Agitation Or Volume Weighing measurement White (Sodium caseinate) (Egg) White + yellow fn (time) Rui Morais QEA 13 13 7 6 5 0, 25% - p H6 0, 25% - p H 9 4 Ln Ve 0, 5% - pH 6 0, 5% - pH 9 3 Line ar (0 ,25% - pH6) Line ar (0 ,25% - pH 9) 2 Line ar (0 ,5% - p H 6) 1 Line ar (0 ,5% - p H 9) 0 0 10 20 30 40 50 Tempo (min.) Ln Ve/2=a t1/2+b Rui Morais QEA 14 14 7 Química e Estrutura dos Alimentos TP 4: Analysis of food products derived from fruits by refractometry Principle: q Determination of the Saccharides content in quince jam. q Refractive index: Useful for confirmation the Identity and Purity Certification/Proofing of food products. q Refractive index = fn (Temperature (T), Wave-lenght (λ), Concentration (C), Chemical nature, …) q ºBRIX = Primary unit of measurement for dissolved solids in the food industry. q BRIX Scale: Corresponds to the % (w/w) Saccharose concentration in a solution: Exp.: 10 ºBRIX = 10 gsucrose/100 gsolution Rui Morais QEA 15 15 Example of a Refratometer: Sample cover Measuring prism Reading in a Refratometer: Place a small drop of the sample on the measuring prism Close the sample cover plate immediately Point the refratometer toward a window or any light source A distinct line can be seen on the instrument scale: (Temperature is automatically compensated!) Rui Morais QEA 16 16 8 Química e Estrutura dos Alimentos Tared beaker Procedure: Extraction of Sample + H2O Sugars Trituration Warming-up: Re-fill H2O: boiling Cool down: room temperature Weigh: m (Solution) (Aliquot) Filter: ºBRIX α Sugar (solution) 1. % Saccharose measurement: Rui Morais QEA 17 Calculations: ü % Saccharose 1 ºBRIX = 1g total dissolved solids (t.d.s.)/100g sample Sample: t.d.s. ≈ Saccharose. THEREFORE: Saccharose weight in 100g SOLUTION: X ºBrix ---------------- 100g Solution m (t.d.s.) (?) ---------- m (Solution) C12H22O11 Saccharose weight in 100g SAMPLE: m (t.d.s.) --------------- m (Sample) % t.d.s. --------------- 100g Sample That is: ü % Moisture Rui Morais QEA 18 9 Química e Estrutura dos Alimentos Procedure: 2. Determination of % Moisture: Tared watch glass : Sample (x3) Weigh: Dry in a oven: 130ºC Repeat until constant weight Excicator Weigh: Rui Morais QEA 19 TP 5: Red-Beet gelly making Principle: q This experiment demonstrates the importance of pectin in jelly making. It also shows how the amount of sugar used affects the jelly. Experiment Jelly Consistency Treatment 1 Regular (Control) formula Treatment 2 Low sugar Treatment 3 High sugar Treatment 4 Low pectin Rui Morais QEA 20 20 10 Química e Estrutura dos Alimentos TP 5: DEVELOPMENT OF BEET-BASED JELLIES Objective : qThis experience demonstrates the importance of pectin in the production of jams. It also shows how the amount of sugar used affects jam production. Rui Morais QEA 21 21 TP 5: TP 5: DEVELOPMENT OF BEET-BASED JELLIES Evaluation: Experiences Type of jelly Consistence Experience 1 Normal (Controle) formulation Experience 2 Low sugar Experience 3 High sugar Experience 4 Low pectin Rui Morais QEA 22 22 11 Química e Estrutura dos Alimentos Pectins gellification model Rui Morais QEA 23 23 12