The Chemistry of Falafel - Lab Report Example

The Chemistry of Food The Chemistry of Falafel Introduction Falafels are a fried ball or patty of spiced chickpeas (garbanzo beans)that are often combined with wheat. However, variations in composition exist: chickpeas have in some cases been substituted with fava beans (Egypt). In Lebanon, they have consisted of both fava beans and chickpeas. It is not only the contents that have varied, but there has also been liberality in Shape and presentation. Placed inside a pocket or a roll of flat bread, are the most typical servings. Yogurt, fresh vegetable, salad, sesame seed, hot sauce, French fries (Israel), hummus or baba Ghan ush for dipping, and tomato sauce are added to compliment the dish. In general falafel can be considered one of Middle East’s famous cuisines. It is highly nutritious both in protein and vegetable (Gisslen & Smith 2010, Pg 697). Most foods are labeled as a prerequisite of the Nutrition Labelling and Education Act of 1990. For proper informative labelling, food must be analysed both for qualitative and quantitative parameters. Most products are thus found with a nutritional label specifying quantities of various minerals and nutrients. The total mineral content of food is often represented by the ash content (Nielsen 2010, pg. 103). Ashing is the first step in elemental analysis of a food sample and so is considered a proximate analysis in nutritional analyses. Fresh foods have been found to rarely have an ash content that is greater than 5%, fats and pure oils are found to have little or no ash. Sodium, iron and calcium content of food due to their contribution to hypertension, osteoporosis and anaemia are frequently labelled in food products (Nielsen 2010, pg. 191). Minerals such as salt have both functional and nutritional properties. Salt fortified with iodine is used to fight goitre. In addition it adds flavour, modifies ionic strength thereby affecting the solubilisation of proteins and other components of food while at the same time acts as a preservative. The moisture content of food plays a significant role in the determination of quality, resistance to deterioration and preservation. In addition, it can be used in the calculation of other constituents e.g. carbohydrate content. Total solids are the weight (dry weight) that remains after moisture analysis (Nielsen 2010, Pg 25). Lipids are compounds that are sparingly soluble in water but have variable solubility in organic solvents such as ethyl ether, petroleum ether, acetone, ethanol, methanol, and benzene (Coultate 2009, Pg 97). Triacylglycerols and phospholipids are considered to be important. Triacylglycerols are liquid (oils) at room temperature and are generally of plant origin. Their solid counterparts are from animals (fats). A process of extraction commonly determines food lipid content. However, the solvents affect the lipid content. Some methods that involve solvent extraction include Soxhlet, Goldfish, and Mojonnier. There also exists non-solvent wet extraction methods such as Babcock, Gerber, and instrumental methods infrared and X-ray absorption that are reliant on physical and chemical properties of lipids. The choice of method is dependent on available instruments, nature of the sample, and the purpose of analysis (Nielsen 2010, Pg 31). Proteins are also one of the most abundant cell components and with the exception of storage proteins are requiredfor cell function and structure (Nielsen 2010, pg 133). They are complex molecules comprising of hydrogen, carbon, oxygen, nitrogen and sulphur. There are twenty α amino acids linked by peptide bonds which are the building blocks of proteins. Nitrogen is the distinguishing factor in proteins and basic amino aicd rich proteins are found to have more nitrogen content. Proteins posses food functional properties; glutenin and gliadin in wheat flour are improtant for breadmaking, caesin in milk that facilitates coagulation and not forgetting egg albumen. Enzymes and enzyme inhibitorsare common for instance in meat tenderizing, and also pectinases and trypsin inhibitors in fruit ripening and legume seeds respectively. Many methods have been developed for the discussion of the protein content of foods. Of these, the Kjeldahl and nitrogen combustion (Dumas) method both of which are based on the determination of nitrogen are most popular (Nielsen 2010, Pg 41). Dietary proteins provide essential aminoacids that are required for synthesis of body proteins and other tissue constituents (Coultate 2009, Pg 168). The human body, provided there are available carbohydrates and nitrogen can synthesize a vast majority of amino acids (non-essential acids), however, some amino acids that cannot be synthesized in the body must be supplied in the diet (essential amino acids). The provision and body requirements (demand) of amino acids should ideally balance. The aim of this experiment is to determine the moisture, fat, salt, protein and ash content that are relevant parameters for food quality Materials and Method 1.1. Method for determination of ash content Equipment: Blender, crucible, analytical balance, Bunsen burner in a fume cupboard, tripod, tongues, muffle furnace at 550oC, desiccator Procedure The falafel sample was homogenized to almost uniform size. An analytical balance was used accurately to weigh a crucible that had been previously ignited and cooled. The mass of the crucible was recorded in a table, and the crucible labeled appropriately. About 2g of the already homogenized falafel sample was weighed into the crucible and the mass of the crucible + sample recorded in the table. The food sample was then ignited over a Bunsen burner placed in a fume cupboard until all the food was completely burnt. The crucible was then transferred to the muffle furnace set at 550 o C for 3 hours. The crucible was then taken out and Cooled in the desiccator. The mass of the crucible plus ash’ was then weighed and recorded. The percentage ash content was then calculated (Nielsen 2010, Pg 103: Kershaw 2013, pg. 8) 1.2. Method for determination of salt content Chemicals: Potassium chromate (KCrO4) 5% solution (yellow to orange) (Mohr method) or Dichlorofluorescein (green to pink) (Fajan’s method), Silver nitrate (AgNO3) reagent, 0.1 M (0.1mole per litre), Or Diluted silver nitrate reagent, 0.01M (* If the sample has less than 1.0% sodium chloride, diluted silver nitrate solution should be used.), Distilled water Equipment: Conical Flask, Burette, and Stand Procedure The falafel sample was ashed according to ashing procedure above. The cooled (cooled in a desiccator) crucible plus ash was weighed on the analytical balance. The ash was washed from the crucible into a conical flask using distilled water ensuring all ash is transferred. 1ml of the indicator (potassium chromate reagent or dichlorofluorescein) was added to the flask using a disposable Pasteur pipette. The burrete was rinsed with Silver nitrate reagent before being filled with the same up to the mark. A 10-fold dilution of silver nitrate reagent was made by transferring 10ml of 0.1M reagent using a bulb pipette to a 100ml volumetric flask and diluting to the mark. The ash sample was titrated with silver nitrate until the first appearance of an orange colour – the sample changed from yellow through to sandy orange to deep orange or a browny orange when dilute silver nitrate solution is used. The volume of silver nitrate reagent was recorded from the burette and is the “titre”. The titration was done in triplicate (Kershaw 2013, pg. 15). 1.3. Determination of Moisture Content Equipment: Blender, Moisture tin, Analytical balance, Oven at 65oC Procedure The mass of falafel was Weighed and recorded. The samples were then homogenized. The moisture tin and lid were Weighed (had previously been dried in the oven and cooled in a desiccator) and Recorded as the ‘Mass of tin’. About 3 g of homogenized falafel sample was weighed into the tin and the mass recorded as (tin + sample) initial weight. The procedure was repeated for two more samples. The lids for each tin were placed under, and tins put in the oven at 65oC overnight. After the heating, the lids were replaced over the tins and the tins let to cool in the desiccator. The tins were then weighed until a constant mass was obtained. This weight was recorded as (tin + sample) final mass. The moisture content was then calculated (Nielsen 2010, Pg 81: Kershaw 2013, pg. 22). 1.4. Determination of fat content of food by sohxlet extraction Chemicals: Soxhlet solvent (Petroleum ether 40 O – 60 O) Equipment: Blender, Sohxlet thimbles (33mm * 94mm paper extraction thimbles), Soxhlet hot extraction beaker (Care! These are very expensive), Sohxlet apparatus: Buchi Extraction Unit E-812/E-812, Oven 50-70 O C Procedure A Hot Extraction Beaker (HEB) was weighed on the analytical balance and the weight recorded. The falafel sample was homogenized in the blender. 10g of the homogenized falafel was weighed using a weighing boat. The weighed falafel sample was put in an extraction thimble and the thimble placed in the HEB. The thimble was placed in a suspension ring, and 40ml of petroleum ether (40oC/60oC) added to the HEB. Extraction took about 1.5h inclusive of a cool down period. The samples were then put in an oven to drive off the last of the solvent (petroleum ether). The samples were weighed and recorded. (Nielsen 2010, Pg. 113: Kershaw 2013, pg. 38). 1.5. Determination of the protein content of food Materials Food sample, Nitrogen free weighing boat, Catalyst tablets, Anti-bump beads concentrated sulphuric acid (in the fume cupboard), Sodium hydroxide 30%, Boric acid 2%, Indicator, Sulphuric acid 0.1M Equipment Blender, Digestion tube, Buchi Speed Digester K-439, digestion apparatus in a fume cupboard, Buchi KjelMaster K-375 distillation, and titration apparatus. Materials Food sample, Nitrogen free weighing boat, Catalyst tablets, Anti-bump beads, Concentrated sulphuric acid (in the fume cupboard), Sodium hydroxide 30%, Boric acid 2%, Indicator, Sulphuric acid 0.1M Equipment Blender, Digestion tube, Buchi Speed Digester K-439, digestion apparatus in fume Cupboard, Buchi KjelMaster K-375 distillation and titration apparatus Digestion The Buchi Speed Digester K-439 was placed in a fume cupboard. Mark a digestion tube with your initials. 0.2g of the falafel sample was weighed into the nitrogen free weighing boat. The boat and its contents were placed in the digestion tube. 2 catalyst tablets and 2 glass beads were then added into the tube. The digestion tube was placed in the rack. 20ml of concentrated sulphuric acid (H2SO4) was added into the tube and the tubes connected to the Buchi digestion apparatus in the fume cupboard. The tubes were heated in the Buchi digestion apparatus for 120 minutes until the contents became clear, and heating continued for an additional 15 minutes. The rack of tubes was removed and left to cool in the fume cupboard. Distillation and Titration The Buchi KjelMaster K-375 distillation and titration apparatus was used for this section. The cooled digestion tube was installed in the Buchi distillation and titration unit. Sodium hydroxide (NaOH, 30% solution) was introduced into the digestion tube to distil the nitrogen into a receiving vessel containing boric acid. The nitrogen from the digest distils as ammonia NH3, using steam, and dissolves as ammonium ions, NH4+, in the boric acid. The distillate automatically titrated with the 0.1M sulphuric acid to neutralize the ammonium ions. The titre: the milliliters of 0.1M sulphuric acid required to neutralize the ammonium was recorded. The distillate can also be titrated manually with 0.1M sulphuric acid in a burette and the endpoint determined using a handheld pH meter (Nielsen 2010, Pg. 131: Kershaw 2013, pg. 44). RESULTS AND DISCUSSION Table 1 Ash content of falafel mass of the crucible (g) mass of crucible + ash (g) sample mass (g) Ash content % 13.1276 15.0538 1.9262 1.0000 9.7011 11.1234 1.4223 0.0012 12.0646 14.1466 2.0820 0.1213 Mean     1.8102 0.3742 STDEV     0.3448 0.5453 (Final mass – Crucible mass)/ Sample mass × 100 = % ash w/w Note “% ash” means exactly the same as “g/100g”. The mean value for ash in ........................ = ......0.3742................... g/100g The standard deviation for this value =............0.5453...............g/100g Table 2 Salt content of falafel Ash weight (Sample mass) (g) titre (ml) salt content % 100g 13.1726 50.0000 0.0222 9.7327 31.0000 0.0186 12.1157 48.0000 0.0232 Mean     0.0213 x 100 = Concentration of sodium chloride in sample (g/100 g) The mean value for salt in ........................ = ......0.0213.................. g/100g The standard deviation for this value =............0.0024...............g/100g Table 3 Moisture content of falafel mass of tin (g) mass of tin + sample initial (g) tin +sample final (g) sample mass (g) moisture content % 23.9527 26.9878 25.6252 1.6725 81.4676 23.9205 26.8978 25.5449 1.6244 83.2861 23.8610 26.7775 25.4696 1.6086 81.3067 Mean 23.9114 26.8877 25.5466 1.6352 82.0170 STDEV 0.0465 0.1055 0.0778 0.0333 1.0993 × 100 = Moisture content g/100g The mean value for moisture in ........................ = ......82.02.................. g/100g The standard deviation for this value =............1.1...............g/100g Table 4 fat content of falafel original sample weight (g) cup weight + fat (g) Empty cup Weight (g) cup + fat weight -empty cup (g) Fat content % 3.0900 163.1237 162.5481 0.5756 18.63 3.0307 163.6495 163.1842 0.4653 15.35 3.1462 162.8862 162.4015 0.4847 15.41 Mean 3.0890 163.2198 162.7113 0.5085 16.46 STDEV 0.0578 0.3906 0.4161 0.0589 1.8757 X 100 = grams of fat per 100 g sample Table 5 Protein content of falafel mass of sample (g) titre (ml) N % protein % 1.0803 7.0530 0.9140 5.8315 1.0451 6.5104 0.8721 5.5641 1.0533 5.1699 0.6872 4.3841 mean 1.0596 6.2444 0.8244 5.2599 STDEV 0.0184 0.9693 0.1207 0.7702 (Titre x 0.0028 x100)/ Mass of sample = N % (percentage of nitrogen in the food, by mass) (Titre x 0.0028 x 100 x factor)/ Mass of sample = Protein % (percentage of protein in the food, by mass) The mean value for protein in ........................ = ......5.26.................. g/100g The standard deviation for this value =............0.77...............g/100g Table 6 Comparison of Nutrition Table from farafel in the experiment and Mccance and Widdowsons Falafel (per 100g) Mccance and Widdowsons (g) Sainsbury falafel (per 100g) Ash Content 0.3742 Salt Content 0.0213 0.7 1.38 Moisture Content 82.02 59 Fat content 16.46 11.2 18.1 protein 5.26 6.4 7.7 Discussion From food analysis experiment, the ash, moisture, salt, fat and protein content of falafel was determined. The average Ash content was found to be at 0.3742g/100mg. From these, the salt content was determined to be 0.0213g/100mg. The moisture content was found to be 82.02 ± 1.1 g/100g. The fat content was found to be 16.46 ±1.88g/100g and the protein content was found to be 5.26 ± 0.77g/100g. When compared to the Mccance and Widdowsons Farafel content (salt 0.7g, Fat 11.2g, moisture 59g, and Protein 6.4g ) it is observed that the contents of the falafel sample is in agreement with reported values except for salt which seems to be much lower. The likely cause for disparity/error in the salt content could be due to preparation method of the falafel. In the terms of the experiment it could be due to incomplete transfer of ash from the crucible into the conical flask. The extraction process (Soxhlet) are also likely cause for error in the analysis process due to incomplete extraction when analysing fat. Errors could arise due to handling of instruments. Sainsbury falafel according to the product label contains per 100g; 18.4g Fat, 7.7g Protein, and 1.38g salt. It is still observed that the experimental salt content is still much lower as compared to product label. However, the fat and protein content are in close agreement. The amount of ash and moisture is not provided. Conclusion The composition of falafel has been successfully determined and found to coincide to values reported by Mccance and Widdowson CoFID and also Sainsbury Falafel nutrition label. It is observed that the salt content for both Mccance and Widdowson and the experiment falafel are lower than that reported by Sainsbury product label. Falafel is a versatile food in terms of composition and presentation. With the ever increasing interest to meet dietary requirements, a knowledge of composition of foods is essential and product labels are an informative tool. At a glance the consumer is made aware of their intake. It is also rich in dietary proteins. Its origin can only be traced into the Middle East but no exclusive claim can be made. REFERENCES COULTATE, T. P. (2009). Food: the chemistry of its components. Cambridge, Royal Society of Chemistry. NIELSEN, S. S. (2010). Food analysis. New York, Springer. GISSLEN, W., & SMITH, J. G. (2010). Professional cooking. Hoboken, N.J., Wiley. Food Standards Agency, (2002) McCance and Widdowsons The Composition of Foods 6th summary edition. (ed Roe M.A. Finglas P.M., & Church S.M.) Cambridge: Royal Society of Chemistry. KERSHAW, J. (2013). The Chemistry of Food 324Z0033. Manchester metropolitan university Read More