Coloranti naturali e colouring foodstuffs: sviluppo di metodi di controllo qualità in una prospettiva industriale

Colour is one of the most important aspects that consumers evaluate when purchasing a food. Due to the increasing interest of consumers toward more natural and sustainable foods even colouring additives, because of their E-number labelling, may be not well accepted. In this context, ingredients with colouring properties, the so-called colouring foodstuffs, are gaining interest. While colour additives are strictly ruled in EU with a defined composition (CAS numbers, control analytical methods and assay for minimum colouring matter content), for colouring foodstuffs all these definitions are still lacking and particularly a reference quality control method. The purpose of this thesis was to develop analytical methods, suitable for an industrial environment and in particular for a quality control laboratory, to characterize colour additives and colouring foodstuffs of interest for the confectionery industry. In particular, UV-visible spectrophotometric methods were developed starting from European legislative references (Reg. 231/2012) to analyse the most common colouring matters used in confectionery products - curcumin (E100), carminic acid/carmines (E120), chlorophyll [E140(i)], β-carotene (E160a), annatto (E160b), paprika (E160c) and betanin (E162) – and then applied on both colour additives and colouring foodstuffs. Since colouring foodstuffs are a mixture of extracts from different vegetable and fruit sources, their UV/Visible spectra are the result of characteristic transitions of several colouring matters and not as pure and defined as that of colour additives. Anyhow experimental results confirmed the effectiveness and reliability of the analytical strategy developed for colour additives on all the analysed colouring foodstuffs. This is due, in most cases, to the prevalence of a specific pigment responsible of the expressed colour. The most relevant difference between colouring foodstuffs and colour additives was indeed the colour intensity. In fact, to obtain comparable colour intensity, higher dosages are needed for extracts compared to colour additives. As a conclusion the developed spectrophotometric methods can be applied in an industrial quality control laboratory to check the conformity of an incoming batch as well as in an R&D lab to support product development by measuring the stability over time of colour in products and eventually adjusting the final dosage to reach the desired target.