# Using Hydrofluorocarbon Extracts of Hop in a Pilot Scale Brewing Process
## 1 Introduction  
Hop (_Humulus lupulus_) is a plant usually used as a fundamental ingredient in the brewing industry. Infloresences of the female \(H\). _lupulus_ plant are rich in essential oils, resins, and polyphenic compounds, which exert a preserving action on the beer and are responsible for its typical flavors and aromas [1]. Moreover, in recent years, pharmaceutical applications of hops have been investigated due to their anti-inflammatory, antiseptic, antidiuretic, hypnotic, and stomachic properties [2]. Furthermore, its sedative effect has been exploited in food supplements for the treatment of sleep disorders [3]. As regards the application in the brewing field, resinous compounds, such as \(\alpha\)- and \(\beta\)-acids, give a bitter taste to beer and may protect the beer against lactic acid bacteria (genera of _Lactobacillus_ and _Pediococcus_) and contribute to the improvement of its foam stability [4]. Moreover, essential oils are responsible for the specific aroma, tannins play a part in the clarification of beer by precipitating proteins during boiling, and hop polyphenol compounds, which represent almost 4% of the total hop dry mass, have been identifiedas important bioactive compounds with strong antioxidant and preserving functions [5; 6]. During the boiling phase of a brewing process, \(\alpha\)-acids are isomerized into iso-\(\alpha\)-acids, (isohumulone, isocobumulone, and isoadhumulone), which play an active role in the antibacterial preservative action of hops, are more soluble in water, and are present in the finished beer in larger quantities than their non-isomerized precursors, providing its distinctive bitter flavor and aroma. \(\alpha\)-acids and \(\beta\)-acids are susceptible to oxygen and degrade rapidly during hop storage [7]. The effects of oxidized hops on the bitterness quality of beer are controversial; [PERSON] and [PERSON] [8] suggested that, although iso-\(\alpha\)-acids were confirmed to be more bitter than oxidized \(\alpha\)- and \(\beta\)-acids, the latter resulted to be bitter enough to have a potentially significant impact on beer bitterness. Several hop products are available for commercial use, such as hop powders or pellets, enriched hop powders or pellets, hop oils, hop extracts, and isomerized hop extracts [9]. Over the years, hop extracts have been used to replace hop powders or pellets in brewing, ensuring the following advantages: better bitterness control between different batches owing to their greater homogeneity, improved hop utilization due to the use of concentrated extracts, improved stability during the storage, which allows the preservation of excess production from one season to the next, and reduced transport and storage costs [10]. Hop extracts consist of a resinous fraction, responsible for the bitter taste of the beer and a volatile fraction that influences the aroma [11]. The resinous fraction represents 20% of the dried cones and is mainly formed by \(\alpha\)-acids (humulone and its congeners, such as cohumulone, adhumulone, prehumulone, and posthumulone) and \(\beta\)-acids (mainly lupulone and its congeners, such as colupulone, adlupulone, prelupulone and postlupulone). The volatile fraction is instead composed of terpen, such as mynce, \(\alpha\)-humulene, and \(\beta\)-caryophyllene, and its content in dried hops can vary from 0.1% to 2% [11]. Moreover, the use of pre-isomerized extracts, such as replacements for conventional hop extracts, guarantee reduced hopping costs without affecting the sensory characteristics of a beer, as confirmed by [PERSON] and [PERSON] [12]. These extracts allow brewers to significantly reduce boiling times, which results in the reduction of energy costs by maintaining flavor stability. Sometimes, they can be added to the worst after fermentation to adjust the bitterness of a finished beer. Steam distillation and organic solvent extraction are the most widespread extraction methods used for the recovery of oils from vegetable matrices.