Comparative Proximate Analysis Of Food Condiment

Introduction

Proximate analysis is a method used in food chemistry for the quantitative determination of composition of different macronutrients present in food materials (Hart, F. L., & Fisher, H. J. 2012). It can be used to provide a very broad classification of food components, to give comparison between foods based on nutritive value as well as to ensure that products made by food- manufacturing companies meet legal requirements and safety standards and also for quality control. One of the greatest merits of proximate analysis is that it is easy and thus cheap to carry out. Some of its disadvantages are that it is not always selective; ammonia is determined as protein and that it cannot be used to directly to determine carbohydrate content (James, C. S. (Ed.), 2013). 

This analysis that was developed in 1860 by Henneberg and Stohmann in Germany. It began with the quest for nutritional analysis during that period and since then it has been continuously developed, modified and improved. It includes determinations of six components that include moisture, protein, fat (ether extract), crude fibre and ash in food (Atasie et.al, 2009). The other materials present in the food sample apart from the ones listed above are all covered by Nitrogen-free extract (NFE). NSE is however not measured by proximate analysis but is calculated by subtracting from moisture, protein, fat, fibre and ash from 100 (Ramzan et.al, 2011).  Thus, NFE represents a rough estimate of all soluble carbohydrate (i.e., sugar and starch).

Whole milk powder is obtained by removal of water and fat from whole milk (liquid). There is usually a small percentage of water and fats left in the whole milk powder. Usually, the whole milk powder contains 26%-40% fat, 3%-5% moisture,   about 35%-40% lactose, 4%-6% ash, and 25%-28% protein (Whetstine et.al, 2007).

The aim of this experiment is to learn and understand the methods employed in determination of the moisture, protein, crude fat and ash content of the whole; to experimentally determine the percentage compositions of such constituents in foodstuffs as well as to learn the principles of determination involved in such methods.

Principle for Determination

Determination of Moisture and Total Solids

The content of food moisture can be determined by a number of methods which vary in their accuracy, cost, speed, sensitivity, specificity, ease of operation, etc. The choice of a method depends on: the kind food being analyzed and its nature (whether easily oxidized or decomposed), accuracy required, availability and cost of equipment, relative amount of moisture in the food product and rapidity of determination. Some of the methods involved include air-oven method, microwave analyser, freeze-drying, Karl-Fisher method, vacuum-oven drying, distillation etc. However, this determination has limitations such as degradation of unsaturated fats and loss of other volatiles (Odebunmi et.al, 2010).

Determination of Ash

Ash in a food product is termed as the inorganic residue that remains after organic matter is totally burned. It measures of the total amount of minerals in food. Ash contents in fresh foods barely above 5%, although some processed foods can have ash contents as high as 12%, e.g., dried beef. Some of the methods used in determination here are dry ashing, wet ashing, microwave ashing, sample preparation etc.

Determination of Nitrogen and Crude Protein

The most common method employed here is Kjeldahl method also called crude protein determination which involves determination of the total amount of reduced nitrogen present in products of protein. It was devised by Johan Kjeldahl who found out that all protein contains almost the same amount of nitrogen (16%). Therefore, we can determine crude protein by analyzing nitrogen content, which is easier, and calculate crudeby multiplying  protein by a factor of 6.25. Other methods include enhanced Dumas method, titration method and other methods that use UV-visible spectroscopy.

Determination of Crude Fat

Foodstuffs have soluble fats in them. Methods used to measure crude fat are either gravimetric like Soxhlet and Mojonnier methods while others are volumetric such as Gerber and Babcock methods. The method used in determination of crude fats is depended on the fat’s insolubility in aqueous systems after it is released from the emulsified state or partition of the fat between an organic solvent and aqueous solution.

Determination of Crude fibre and Carbohydrates

Carbohydrate that is contained in the food has two fractions, the crude fibre (CF) and the nitrogen-free extract (NFE). To determine crude fibre, residual food from ether extracts is subjected to a reaction of acid and concentrated alkali under a high temperature. The reaction produces an organic residue that is called crude fibre. To determine the nitrogen-free extract, you take sum of the moisture content, ash, crude protein, ether extract and crude fibre (expressed in g/kg) is subtracted from 1000. The nitrogen-free extractives fraction is a heterogeneous mixture of all those components not determined in the other fractions.

References

Hart, F. L., & Fisher, H. J. (2012). Modern food analysis. Springer Science & Business Media. Atasie, V. N., Akinhanmi, T. F., & Ojiodu, C. C. (2009). Proximate analysis and physico-chemical properties of groundnut (Arachis hypogaea L.). Pakistan Journal of Nutrition, 8(2), 194-197.

James, C. S. (Ed.). (2013). Analytical chemistry of foods. Springer Science & Business Media.

Odebunmi, E. O., Oluwaniyi, O. O., & Bashiru, M. O. (2010). Comparative proximate analysis of some food condiments. J. App. Sci. Res, 6(3), 272-274.

Ramzan, N., Ashraf, A., Naveed, S., & Malik, A. (2011). Simulation of hybrid biomass gasification using Aspen plus: A comparative performance analysis for food, municipal solid and poultry waste. Biomass and Bioenergy, 35(9), 3962-3969.

Whetstine, M. E. C., & Drake, M. (2007). The flavor and flavor stability of skim and whole milk powders.