Abstract
This study investigated the use of conventional and innovative extraction methods to produce food-grade hop extracts with high antioxidant capacity and content in bioactive compounds. Conventional extractions (CONV) were performed under dynamic maceration at 25 and 60 °C; innovative extractions were performed using two ultrasound systems, a laboratory bath (US) and a high-power ultrasound bath (HPUS), and a high-pressure industrial process. For CONV, US, and HPUS extractions the effect of the extraction time was also tested. Experimental results showed that extraction method, temperature, and time affect to a different extent the phenolic profile and have a significant effect (p < 0.05) on the total phenolic content, total flavonoid content, antiradical capacity (ABTS), chlorophyll α, and total carotenoids content. Overall, US and CONV 60 °C extractions showed the highest extraction efficiency for almost all the investigated compounds, however, the extraction method and time to be used strongly depends on the target compounds to extract.
Highlights
In food productions, the use of plant extracts represents a strategy of growing interest to replace the use of chemical and synthetic additives or ingredients with functional properties and technological functionalities and to satisfy the demand of the stakeholders and consumers for innovative, high quality, healthy, clean labels, and sustainable food products
This study investigated the use of conventional and innovative extraction methods to produce food-grade hop extracts with high antioxidant capacity and content in bioactive compounds
The increase of Total phenolic content (TPC) and Total flavonoid content (TFC) with the increase of the extraction temperature is in accordance with the results presented by other authors on different plant matrices [31,35] and attributed to various factors, including (I) the breakdown and release of free phenols otherwise covalently bound with plant cell insoluble polymers, (II) increased phenolic solubility, (III) the increase of mass transfer rate; and of the extraction rate, and (IV) the reduction of solvent viscosity and surface tension [35,36,37]
Summary
The use of plant extracts represents a strategy of growing interest to replace the use of chemical and synthetic additives or ingredients with functional properties and technological functionalities and to satisfy the demand of the stakeholders and consumers for innovative, high quality, healthy, clean labels, and sustainable food products. Plant extracts could be used to fortify food products with polyphenols [3], whose consumption has been inversely associated with the risk of developing diseases linked to oxidative stress [4]. In this frame, the female inflorescence of hops (Humulus lupulus L.), known worldwide for its use in brewing production, represent a rich source of antioxidants and other compounds with biological activity. The multiplicity of beneficial effects exerted by hops are attributed to the high content of bioactive compounds and, in particular, to three main groups of secondary metabolites i.e., resins, essential oils, and polyphenols [7], whose presence and concentration depends on variety, harvest time and year of production [5,8]
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