Abstract
Increasing consumer demand for natural flavours and fragrances has driven up prices and increased pressure on natural resources. A shift in consumer preference towards more sustainable and economical sources of these natural additives and away from synthetic production has encouraged research into alternative supplies of these valuable compounds. Solid-state fermentation processes support the natural production of secondary metabolites, which represents most flavour and aroma compounds, while agro-industrial by-products are a low-value waste stream with a high potential for adding value. Accordingly, four filamentous fungi species with a history of use in the production of fermented foods and food additives were tested to ferment nine different agro-industrial by-products. Hundreds of volatile compounds were produced and identified using headspace (HS) solid-phase microextraction (SPME) coupled to gas chromatography–mass spectrometry (GC–MS). Four compounds of interest, phenylacetaldehyde, methyl benzoate, 1-octen-3-ol, and phenylethyl alcohol, were extracted and quantified. Preliminary yields were encouraging compared to traditional sources. This, combined with the low-cost substrates and the high-value natural flavours and aromas produced, presents a compelling case for further optimisation of the process.
Highlights
A high consumer demand for natural flavour and aroma compounds has increased the pressure on traditional, natural sources of many natural additives [1]
All substrates were >90% surface covered by mycelia 10 days post-inoculation with the exception of five fermentations: Aspergillus niger on red grape marc; Penicillium camenberti on olive cake and red grape marc; and Pycnorporus cinnabarinus, on spent brewer’s grain, and red grape marc
Over 50 metabolites of interest were identified across the fermented substrates, mostly molecules associated with flavours and aromas
Summary
A high consumer demand for natural flavour and aroma compounds has increased the pressure on traditional, natural sources of many natural additives [1]. Natural flavours and fragrances are traditionally sourced from herbs, spices, plants, and animals—usually in the form of essences, extracts, and oils. Commercial demand for such products often outstrips global supply and prices can be volatile. Microorganisms have been used to produce and enhance flavours in food and beverage products for centuries, for example, cheese, wine, and chocolate [2,3]. There has been a resurgence of using fermentation to produce consumer goods [4]. Various fungi and yeasts have been investigated for their potential to produce aroma compounds, including Rhizopus spp., Trichoderma spp., Ceratocystis spp., Saccharomyces spp. Hanseniaspora spp. [5,6,7,8,9,10,11,12]
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