So what is a bitter, excepting an English top-fermented ale ? According to web encyclopedia Wik ipedia, it is: "A preparation of herbs and citrus dissolved in alcohol or glycerine with a bitter or bittersweet flavour. The brands, once numerous, were formerly manufactured as patent medicines, often served as digestifs. The few remaining varieties are principally used as aperitifs or as flavourings in cocktails."

There is also amaro, or amaro alle erbe, which is the Italian equivalent, described as an Italian herbal after-dinner digestif liqueur. The best known brands are Amaro Averna and Pernod Ricard's Amaro Ramazzotti.

Pernod Ricard itself describes bitters as: "Spirits flavoured with bitter plants. The infusion, maceration and blending processes are often very old. Bitters may be served as an aperitif or a digestif. They may also be used to make cocktails."

Bitters account for 4 per cent of Pernod's spirits business (by volume), so it is a significant category for the world's second largest drinks company. Its major brand apart from Ramazzotti, which sells well in Germany (number one imported spirit with sales approaching one million 9-litre cases, according to IWSR data), is Suze in France. It also owns Fernet Capri and Becherovka (Czech Republic).

Euromonitor International classifies bitters as a subcategory of liqueurs. In its most recent global overview, it says traditional local liqueurs "suffer from changing patterns of spirits consumption ". It  adds that urbanisation with "accelerated lifestyles and smaller households have disrupted habits such as consuming liqueurs as part of leisurely meal times ".

The traditional role of bitters as after-dinner digestifs has all but gone and their role as a pick-me-up/hangover cure ("hair of the dog "), is not politically correct in this age of concern over alcohol and health. The kiss of death is that younger drinkers regard the category as ­old-fashioned.

The major bitter brands are arguably Jägermeister, Angostura and Underberg. Campari is made from bitters but most would regard that as a mainstream spirit brand/aperitif. The other big brands, such as Fernet Branc (Italy), Gammel Dansk (Denmark), Kuemmerling (Germany), Araucano (Chile) and Unicum (Hungary) are, in the main, more regional or national , whereas the aforementioned have breached their national boundaries and - certainly in the case of Jägermeister and Angostura - positioned themselves as a bitter and a contemporary brand that can be mixed.

Angostura is one of the oldest contemporary mixers. Formulated around 1824 by a German doctor in Venezuela for stomach illnesses, it found its way to Trinidad and England where it was picked up by the British Royal Navy as a cure for sea sickness and gastric ailments but also, more importantly, for the officer class's pink gins. Ironically, Angostura was named after the Venezuelan town but contains no angostura bark.

Peychaud Bitters, the New Orleans-associated gentian-based bitter, is also associated with a particular drink - the cocktail sazerac.

This year Angostura, now owned by Trinid ad-based CL World Brands, which also owns Hine Cognac, Belvedere, Marie Brizard and Burn Stewart, launched its first new product in 200 years - Angostura Orange Bitters. Brand ambassador Mickael Perron says the company discovered in discussions with bartenders and mixologists that in the world of cocktails, "no single flavour has been as versatile as orange".

International brand manager Alison Getty, like so many, is adamant that Angostura is not in the traditional bitters sector. "We are not playing in the bitters sector," she says. "Angostura is for mixing in cocktails, non-alcoholic drinks and with food."

Within five years Jägermeister has gone from a one million case brand to three million in the US, overtaking its historical number one market, Germany.

Jack Blecker, Mast-Jägermeister 's international sales and marketing director, says: "We have been working for a long time all round the world on not being perceived as a bitters brand. we do not have a 'one-and-only marketing activities blueprint' for all our markets. We think and act locally."

The company focuses on young adults and has a programme of sponsored youth-orient ed events such as rock concerts. Jägermeister is strongly associated with the "bomb ritual" of shot drinking and the "flying hirsch", in which a Jägermeister miniature is dropped into a glass with an energy drink.

Blecker says: "In most of the markets around the world we are positioning Jägermeister as a shot brand. Consequently, our main competitors are local shot brands or international shots like Jack Daniels or Jose Cuervo."

Martin Bjelgaard, marketing director of V&S Distillers, which owns Danish bitter brand Gammel Dansk, acknowledges the success of Jägermeister in positioning itself as mixer and ice-cold shot.

He also sees Averna and Ramazotti as having been successful in making themselves appealing to younger adults.

Jägermeister and similar brands he defines as party brands, mixers and shots for younger drinkers, while Ramazotti, Averna and "Campari-type" bitters are aimed at more mature drinkers for use as an aperitif or digestif.

The classics are the "full bitters" such as Gammel Dansk (old Danish), Fernet Branca which he says are more traditional for mature consumers in a "relaxed, wind-down occasion". These bitters, he adds, are often used as a chaser to beer.

Nevertheless, he believes the sector has been stuck in a vacuum.

"The industry has an innovation problem within the category due to the very local origin of many bitters. Many brands have not changed profile or position in the past 30 to 40 years, leading to lost sales and shares.

"We at V&S Distillers have also been trapped in this innovation vacuum for a period, being a local Nordic player in the bitters category. But recently we have begun to realise the vast potential in the category and in our own brands," says Bjelgaard.

In January V&S introduced a new bitter, Malteser, into the German market and in August i t unveiled Gammel Dansk Asmund, named after master distiller and blender JK Asmund who invented the original brand. The ingredients are aged in 350-litre French Limousin oak casks used for Cognac. The taste is described as warm and rounded with notes of vanilla, coffee and cocoa beans.

Bjelgaard believes that, with the quest for new flavours, colours and sensations combined with lower alcoholic strengths, there is a place among modern drinkers for bitters.

The problem for bitters as a category is that the brands cannot speak with one voice like vodka or whisky. Gammel Dansk is a three million-litre brand and bitters is the second largest spirits category in Denmark with a 15 per cent share, but it is virtually unknown outside the country and certainly outside Scandinavia.

As Bjelgaard says, the local nature of bitters makes it "difficult". Euromonitor states: "The sector's development was constrained by the poor performance of traditional liqueurs in markets such as France and Italy in western Europe and Slovakia and Hungary in central/eastern Europe."

Michael Jordens, of Averna, which he describes as a "sweet bitter like Jägermeister", believes the happy hour/cocktail sector is still "quite an untapped opportunity for bitters". His brand and Pernod Ricard's Amaro Ramazzotti have done well in Germany primarily because of that country's love of the Italian/Mediterranean lifestyle. He also points out that sweeter bitters have a significant advantage with women who, generally speaking, have a sweeter tooth than men.

Of the major brands, Underberg has remained steadfastly traditional as a natural herbal digestif, best after a meal. It is available in more than 100 countries and claims to be number one in duty -free/travel retail. The leading brand in the herbal bitter sector, it still comes in the single shot 20ml bottle, but ask Underberg's Nicole Christen how bartenders should or could serve it and she says they should stick to the traditional way.

"Underberg should be drunk neat. All barmen or waiters should serve Underberg in the original, closed portion-sized bottle at the table. Open the bottle in front of the consumer and pour it in the Underberg tall glass - that is how to offer Underberg in a stylish way," she advises.

The bitters sector is so disparate that it is difficult, if not impossible, to generalise about. Certain brands have carved a niche or jumped on the shot and/or mixer/cocktail bandwagons. If there is a move away from clear, neutral spirits towards more exotic, demanding flavours then bitters with their authenticity, traditions, histories and medicinal claims should be well placed to exploit that trend.