Humulus lupulus: From Field to Glass and Beyond

A special issue of Plants (ISSN 2223-7747).

Deadline for manuscript submissions: closed (2 April 2023) | Viewed by 10013

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Guest Editor
CREA Research Centre for Olive, Fruit and Citrus Crops, Via di Fioranello 52, 00134 Rome, Italy
Interests: natural products; bioactive food components; phytotherapy; antioxidants; natural products chemistry; green chemistry; biomaterials; circular economy
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Dear Colleagues,

Hops (Humulus lupulus L.), a perennial climbing herbaceous plant belonging to the Cannabaceae family, is an essential ingredient in beer production, where its female inflorescence (cone or strobile) is used. The plant is native to many temperate areas, including Europe, Asia and North America. Depending on the area of production and aromatic characteristics, different types of hops can be distinguished, differing in aroma and percentage of alpha-acids, a set of chemical compounds that define the bitterness imparted to beer. However, its therapeutic properties have been known since ancient times. The Ayurvedic pharmacopoeia recommends hops as a sedative, to treat headaches and in cases of indigestion. In traditional Chinese medicine, it is used to treat insomnia, restlessness, and lack of appetite. Germany has authorised hops as a standard medicinal tea and markets several sedative drugs containing hop extract. In Germany and the US, hop infusions, tinctures and dry extracts are used in sedative preparations for anxiety and agitation. Strobile and hop extract have been included in the US National Formulary for the formulation of sedative preparations for the treatment of anxiety symptoms. All these properties are due to the plethora of bioactive compounds that characterise hop cones. However, the mechanisms of action are not well understood, and human studies are still few.

The aim of this special issue is therefore to present up-to-date studies on various aspects of Humulus lupulus. Agronomic, physiological, biochemical, qualitative, and ethnobotanical aspects will be considered, as well as the various application aspects for brewing and botanical uses. Particular attention will be paid to studies concerning the extraction, formulation, and characterisation of hop extracts for various fields of use. Economic and social studies related to this fascinating plant will also be included.

Dr. Katya Carbone
Guest Editor

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Keywords

  • hops
  • Humulus lupulus
  • agronomic traits
  • yield and quality improvement
  • plant pathology
  • hop biochemistry
  • hops bioactive compounds
  • bioactive extracts
  • extract formulation
  • botanicals

Published Papers (4 papers)

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Research

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14 pages, 941 KiB  
Article
From Hop to Beer: Influence of Different Organic Foliar Fertilisation Treatments on Hop Oil Profile and Derived Beers’ Flavour
by Margherita Rodolfi, Antonio Valentoni, Luca Pretti, Manuela Sanna, Simone Guidotti, Ilaria Marchioni and Tommaso Ganino
Plants 2023, 12(9), 1861; https://doi.org/10.3390/plants12091861 - 30 Apr 2023
Viewed by 1473
Abstract
Foliar fertilisation is known to influence the physiological response of Humulus lupulus (hop plants), but its effect on the flavour profile of beer still has to be investigated. By comparing the effects of four fertilisation treatments, this study aims at determining whether different [...] Read more.
Foliar fertilisation is known to influence the physiological response of Humulus lupulus (hop plants), but its effect on the flavour profile of beer still has to be investigated. By comparing the effects of four fertilisation treatments, this study aims at determining whether different foliar fertilisation treatments have a significant impact on hop plants’ aromatic quality and that of the beer produced. Hop cones harvested from each experimental treatment were brewed to obtain five single dry-hopped beers, which were subsequently analysed. Gas chromatography–mass spectrometry (GC-MS) and electronic nose (Cyranose 320) analyses were performed on the hop cones, while headspace solid-phase microextraction–gas chromatography–mass spectrometry HS-SPME-GC-MS, electronic nose and sensory analyses were carried out on the beers produced. The analyses not only allowed for a differentiation between the hops from the four fertilisation treatments and the control but also enabled a differentiation between the beers produced for their identification. Sensory evaluation revealed consumer preferences regarding the dry-hopped beers analysed, evidencing their distinctive features, including significant differences in both aroma and flavour. Full article
(This article belongs to the Special Issue Humulus lupulus: From Field to Glass and Beyond)
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15 pages, 3053 KiB  
Article
Relationship between Total Antioxidant Capacity, Cannabinoids and Terpenoids in Hops and Cannabis
by Philip Wiredu Addo, Zohreh Poudineh, Michelle Shearer, Nichole Taylor, Sarah MacPherson, Vijaya Raghavan, Valérie Orsat and Mark Lefsrud
Plants 2023, 12(6), 1225; https://doi.org/10.3390/plants12061225 - 08 Mar 2023
Cited by 1 | Viewed by 2274
Abstract
Efficient determination of antioxidant activity in medicinal plants may provide added value to extracts. The effects of postharvest pre-freezing and drying [microwave-assisted hot air (MAHD) and freeze drying] on hops and cannabis were evaluated to determine the relationship between antioxidant activity and secondary [...] Read more.
Efficient determination of antioxidant activity in medicinal plants may provide added value to extracts. The effects of postharvest pre-freezing and drying [microwave-assisted hot air (MAHD) and freeze drying] on hops and cannabis were evaluated to determine the relationship between antioxidant activity and secondary metabolites. The 2,2-diphenyl-1-picrylhydrazine (DPPH) reduction and ferric reducing ability of power (FRAP) assays were assessed for suitability in estimating the antioxidant activity of extracted hops and cannabis inflorescences and correlation with cannabinoid and terpene content. Antioxidant activity in extracts obtained from fresh, undried samples amounted to 3.6 Trolox equivalent antioxidant activity (TEAC) (M) dry matter−1 and 2.32 FRAP (M) dry matter−1 for hops, in addition to 2.29 TEAC (M) dry matter−1 and 0.25 FRAP (M) dry matter−1 for cannabis. Pre-freezing significantly increased antioxidant values by 13% (DPPH) and 29.9% (FRAP) for hops, and by 7.7% (DPPH) and 19.4% (FRAP) for cannabis. ANOVA analyses showed a significant (p < 0.05) increase in total THC (24.2) and THCA (27.2) concentrations (g 100 g dry matter−1) in pre-frozen, undried samples compared to fresh, undried samples. Freeze-drying and MAHD significantly (p < 0.05) reduced antioxidant activity in hops by 79% and 80.2% [DPPH], respectively and 70.1% and 70.4% [FRAP], respectively, when compared to antioxidant activity in extracts obtained from pre-frozen, undried hops. DPPH assay showed that both freeze-drying and MAHD significantly (p < 0.05) reduced the antioxidant activity of cannabis by 60.5% compared to the pre-frozen samples although, there was no significant (p < 0.05) reduction in the antioxidant activity using the FRAP method. Greater THC content was measured in MAHD-samples when compared to fresh, undried (64.7%) and pre-frozen, undried (57%), likely because of decarboxylation. Both drying systems showed a significant loss in total terpene concentration, yet freeze-drying has a higher metabolite retention compared to MAHD. These results may prove useful for future experiments investigating antioxidant activity and added value to cannabis and hops. Full article
(This article belongs to the Special Issue Humulus lupulus: From Field to Glass and Beyond)
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16 pages, 1859 KiB  
Article
The Stability of Hop (Humulus lupulus L.) Resins during Long-Period Storage
by Ksenija Rutnik, Miha Ocvirk and Iztok Jože Košir
Plants 2023, 12(4), 936; https://doi.org/10.3390/plants12040936 - 18 Feb 2023
Cited by 4 | Viewed by 1864
Abstract
The stability of alpha-acids, beta-acids and hop storage index (HSI) values under different conditions (aerobic/anaerobic, 4 °C/room temperature) was studied in a two-year trial. Six different varieties (Celeia, Aurora, Bobek, Styrian Gold, Savinjski Golding and Styrian Wolf) were used in the form of [...] Read more.
The stability of alpha-acids, beta-acids and hop storage index (HSI) values under different conditions (aerobic/anaerobic, 4 °C/room temperature) was studied in a two-year trial. Six different varieties (Celeia, Aurora, Bobek, Styrian Gold, Savinjski Golding and Styrian Wolf) were used in the form of cones and pellets. Alpha- and beta-acids were determined by HPLC and HSI by spectrophotometry. Anaerobic conditions at 4 °C were best for alpha-acids, beta-acids and HSI values; however, 10–35% of the alpha-acids were still lost after two years. The decline was greater (63–99%) under aerobic conditions and at room temperature. Alpha-/beta-acid ratios increased in hop cones and decreased in hop pellets, whereas HSI values increased in all storage conditions. Overall, the performance was better for pellets than for hop cones. Storage conditions, storage form and hop variety had significant effects on the stability of hop resins. Full article
(This article belongs to the Special Issue Humulus lupulus: From Field to Glass and Beyond)
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Review

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29 pages, 3586 KiB  
Review
An Updated Review of the Genus Humulus: A Valuable Source of Bioactive Compounds for Health and Disease Prevention
by Katya Carbone and Fabio Gervasi
Plants 2022, 11(24), 3434; https://doi.org/10.3390/plants11243434 - 08 Dec 2022
Cited by 14 | Viewed by 3691
Abstract
The medicinal potential of hop (Humulus lupulus L.) is widely cited in ancient literature and is also allowed in several official pharmacopoeias for the treatment of a variety of ailments, mainly related to anxiety states. This is due to the plethora of [...] Read more.
The medicinal potential of hop (Humulus lupulus L.) is widely cited in ancient literature and is also allowed in several official pharmacopoeias for the treatment of a variety of ailments, mainly related to anxiety states. This is due to the plethora of phytoconstituents (e.g., bitter acids, polyphenols, prenyl flavonoids) present in the female inflorescences, commonly known as cones or strobili, endowed with anti-inflammatory, antioxidant, antimicrobial, and phytoestrogen activities. Hop has recently attracted the interest of the scientific community due to the presence of xanthohumol, whose strong anti-cancer activity against various types of cancer cells has been well documented, and for the presence of 8-prenyl naringenin, the most potent known phytoestrogen. Studies in the literature have also shown that hop compounds can hinder numerous signalling pathways, including ERK1/2 phosphorylation, regulation of AP-1 activity, PI3K-Akt, and nuclear factor NF-κB, which are the main targets of the antiproliferative action of bitter acids and prenylflavonoids. In light of these considerations, the aim of this review was to provide an up-to-date overview of the main biologically active compounds found in hops, as well as their in vitro and in vivo applications for human health and disease prevention. To this end, a quantitative literature analysis approach was used, using VOSviewer software to extract and process Scopus bibliometric data. In addition, data on the pharmacokinetics of bioactive hop compounds and clinical studies in the literature were analysed. To make the information more complete, studies on the beneficial properties of the other two species belonging to the genus Humulus, H. japonicus and H. yunnanensis, were also reviewed for the first time. Full article
(This article belongs to the Special Issue Humulus lupulus: From Field to Glass and Beyond)
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