Approaches to Food Analysis

What is food analysis

The scientific investigation of the physical, biological and chemical attibutes and components of foods.

Physical attributes food analysis

Texture, rheology, mouthfeel, colour, structure etc.

Biological attributes food analysis

Microbiological state and the biological origin of the ingredients

Chemical attributes of food analysis 

Chemical composition of the food product, compounds derived through processing, macros/micros, allergens and contaminants. 

Why analyse foods 

Peace of mind to customers, retailers, manufacturers etc, providing transparent information pertaining to the safe composition/handling requirements of food products. 

Why do manufacturers constantly iterate products 

Reformulations for diet, cost, ingredient availability etc. 

Why is the way food impacts health essential

For improving diets and health worldwide - a very high proportion of global mortality is due to poor diets. 

FA relevance NPD

Uses physical, chemical and biological testing for the development of new products. 

FA relevance QC/QA

Will employ food analysis to confirm expected quality.

FA relevance Sensory

Often complemented by other methods of food analysis. 

FA relevance healthcare

Nutritionists and dietitians base their recommendations and assessments on the chemical composition of patients' diets.#

There is constant research into the effect of different components of food on our health and wellbeing, both positive and negative.

Food analysis conduction - food manufacturers 

Suppliers, goods in, pre/mid processing, final product.

Food analysis conduction - private analytical companies

Require suitable accreditiation e.g., UKAS to ISO17025:2005

Food analysis conduction - official food control laboratories

Chemical analysis (agricultural/public) or microbiological analysis (by a food examiner).

Essential food analysis

This analysis is necessary for legal nutritional information of products. Specific compositional data must be provided, assessed through analytical techniques or databases of similar products.

Voluntary/exploratory food analysis 

Not legally required.  

Typically conducted by manufacturers or researchers to enhance understanding of a product. 

 Used for product improvement, reformulations, or monitoring specific analytes. 

Assesses quality characteristics like colour, texture, and rheology. 

Proximate analysis

The umbrella term that covers most of the analyses of the groups of nutrients legally required for nutritional labelling.

Conducted on the crude extracts of foods and provides the total amounts of each of the nutrients.

These include proteins, fats, carbohydrates, moisture and ash.

Moisture determination

It is an important parameter for understanding properties such as texture, rheology, water activity and shelf life. It is also naturally highly variable, especially in plants.

Not required for labelling but knowing the water content is essential for the other methods. This allows conversion between fresh weight (weight/water) and dry weight (solids only) and enables subsequent calculations of other nutrients.

Protein determination

The primary methods for protein determination are the Kjeldahl and Dumas methods, both of which measure nitrogen content and convert it back to protein content.

Non-protein sources of nitrogen, like nucleotides and urea, can affect some analytical methods, why must their presence be considered.

The Kjeldahl method minimizes the impact of non-protein nitrogen such as urea, while the Dumas method provides total nitrogen measurement.

Difference between the Kjeldahl method and Dumas method 

The Kjeldahl method minimizes the impact of non-protein nitrogen, while the Dumas method provides total nitrogen measurement.

Nitrogen to protein

Kjeldahl and Dumas methods do not directly measure protein; instead, they detect nitrogen from the sample, which is then converted to total protein using conversion factors.

What is the standard nitrogen to protein conversion factor?

6.25 Some proteins with smaller amino acids or more nitrogen may require lower conversion factors.

Lipid determination methods

Continuous solvent extraction (Soxhlet)

Mixed solvent extraction 

Acid hydrolysis 

What do the main methodologies for the determination of fat content determine

Assess total fat for nutrition labelling

Gas chromatography for lipids

Gas chromatography can further analyse fat extracted by Soxhlet or similar gravimetric methods.

This can allow determination of the composition-specific fatty acids in the sample, e.g., saturated vs unsaturated.

What does gas chromatography do

Allows to take a complex mixture of similar chemical components, in this case a mixture of fatty acids, and separate and quantify each individual component.

What does gas chromatography measure

The proportion of each fatty acid in a fat extract can be accurately determined and, from this, the total saturated and unsaturated fat content. 

What is the issue with carbohydrates?

Carbohydrates are a diverse group of compounds, varying from simple monomers to large polymers. Some carbohydrates, known as dietary fiber, are indigestible for humans. In the original proximate analysis system, this distinction was less significant because ruminants can effectively digest complex carbohydrates.

AOAC/Prosky method for determining total dietary fibre (TDF) in foods.

Separates free sugars, starch, and NSP, then accounts for protein and ash to accurately measure the total dietary fibre content of a food.

Ash

Inorganic components of the sample are present once the organic material is destroyed.

Consists of minerals, metals and salt, accounting for a large proportion of the weight.

How to determine mineral content of food

Removal of organic compounds is done by combustion in a muffle furnace with the sample in a crucible.

Analysis by colourimetry, atomic absorption spectroscopy or flame photometry.