Autoclaves and retorts

Autoclave and retort are two names for pressure cooking vessels used in food manufacturing to sterilise canned food and in later versions by engineering firms to cure rubber tyres. The starting point was known as a steam digester, attributed to French scientist Denis Papin, in 1679.

The hazards of working with steam under pressure very quickly became apparent and Papin devised a safety valve to mitigate the risk of explosion, leading many to refer to it as the Papin digester. It was called a digester because it was generally used to apply heat and pressure to bones, leaving cooked bones soft and friable for bonemeal. Other processes were developed for this piece of equipment, from which Papin developed a prototype steam engine. This was subsequently developed into the static steam engines built by Thomas Newcomen.

Chevalier-Appert, a nephew of Nicolas, invented the first reliable pressure gauge for retorts and autoclaves in 1852. This was an essential accessory to prevent explosions and standardise the process. Early retorts comprised a steel vessel, with a metal basket to hold filled bottles or cans. Later versions were fitted with systems that allowed product to be rotated as it cooked, reducing the cooking time. To start a cooking cycle, the vessel is loaded and the door closed. Steam is brought into the cooking chamber and the contents cooked for the required time at the necessary temperature. Once cooked, the steam was turned off and the retort allowed to cool.

A cooking cycle can last for hours, not finishing until the centre of the load had been subjected to a predetermined temperature and for a set period of time. The result is overcooked product on the outside to be sure that the centre cooked properly. Later refinements include automated loading, a key advance to raising throughput.

The Shaka principle

The next milestone, in the late twentieth century, was reached by Richard Walden, a process engineer working for Carnaud-Metalbox. Convinced that it was time to make retorts more efficient, he devised what is now referred to as the Shaka retort, which shakes its load backwards and forwards, driven by a reciprocating actuator at speeds of more than 100 cycles per minute.

Richard Walden

It was clear from the outset that when the prototype reached a certain speed, the load underwent a quantum cooking effect, a “sonic boom” for food, so to speak. Depending on the consistency of the product, cooking time went down dramatically. Further details are available here:

Walden fixed the amplitude on the prototype at around 150mm and varied the speed or rpm on reciprocating arm. For any given product viscosity, Walden could identify a threshold at which a quantum heat transfer took place in the cooking vessel. Further increases in the rpm had no significant effect on cooking times.

John Emanuel signed up manufacturers

Shaka is an undisputed milestone achievement, but has yet to persuade mainstream food manufacturers to scale down their investments in energy-hungry retort lines. The technology has been licensed to two retort manufacturers, Steriflow in France and Allpax in the USA. Prototype, pilot and production models are all available. Although the Shaka units are smaller than their conventional counterparts, they can achieve the same throughput with multiple shorter cooking cycles.

A revolution in the making

The Appertisation of food launched a slew of events that led us to greet the dawn of industrialisation. In the early years of the French revolution, confiseur Nicolas Appert standardised a process that was doubtless known to many at that time. Appert’s single-minded work on heat treating sealed jars, bottles and metal canisters occupied him for years. He filled notebooks and diaries with his observations, recording in minute detail the empirical foundations of his research. Nicolas Appert was a member of the revolutionary Lombard section, radical protesters who took to the streets of Paris at moments of high tension in the French revolution.

A confiseur is a cook who prepares a range of savoury and sweet dishes that have been given long slow cooking until the food almost turns to mush. The standard equipment in a confiseur’s workshop of the time was a copper of boiling water and seasonal ingredients. Today, the word confiserie refers to boiled sugar confectionery, although it probably covered a wider range of foodstuffs in Appert’s day. Most of the confiseur’s stock lines were sealed with a layer of fat and had no shelf life to speak of.

However, Appert’s sealed bottles could be stored with increasing reliability. This “time travel for food”was a pivotal discovery for the future of urban life. As word spread of Appert’s achievements spread across the French capital, Appert was awarded a substantial sum in gold coins, on condition that he put his method into the public domain. A copy of Appert’s instructions reached Bordeaux wine merchant Pierre Durand, who promptly patented the idea in England. As an early trader in intellectual property, Durand struck a number of deals, including one with engineer Bryan Donkin in Bermondsey. The events that followed are covered elsewhere in this blog, in a short story.

The development of Appertisation as a commercial process led to a scaling up of the cooking process. What started out as a hot water bath was reworked as an autoclave or retort. In 1852, one of Nicolas Appert’s nephews, Raymond Chevalier-Appert patented a key component for an retort — a manometer or pressure gauge.

Of Brexit and dogs’ dinners

For years the Common European Tariff has ensured that imports of third country pet food have been taxed heavily at the border. Duty of up to EUR 948/tonne is added to the invoice price of any dog food that might cross the EU border. The exact rate depends on the product’s composition. During the UK’s years as an EU member state, UK customs officials were ready and waiting to do their bit to ensure that third country pet food did not arrive unchallenged by officialdom. Needless to say, a duty regime as strong as this has successfully excluded products which faced duty out of all proportion to their price.

Click the image to download Schedule XIX, then go to file page 93, which is folio 87. (A folio is a printer’s name for the number on a page, the numbering of which may be dislocated by front matter, such as prefaces and other preliminary matter.)

That was then and this is now. We have been through Brexit, which remains a work in progress. As the world’s most recent third country, has the UK risen to the challenge and opened the gates to imports of third country pet foods? Have the punitive levels of duty been dismantled in the UK’s Schedule XIX? Guess.

The table shows the current duty rates for goods covered by customs code 2309 10 – Dog or cat food, put up for retail sale (highlighted in yellow). Click the image to download the complete document. Betweentimes, the tariffs have been redenominated in GBP at an exchange rate of around 85 pence to the Euro. Depending on the formulations, these products face duty up to GBP 805/tonne and are essentially unchanged. Given the stated aim of Brexit to boost trade with the rest of the world, it would have been simple to edit the twenty or so tariff lines, setting them to zero, job done.

The irony of the Brexit debacle is that it neither achieved any of its wild dreams, nor were any logical adjustments carried out to meet Brexit’s stated aim of trade liberalisation. The Common European Tariff (CET) was drafted as a blunt instrument to suggest that the cost of subsidised products under the Common Agricultural Policy (CAP) could be calculated with a degree of accuracy. The CAP has evolved since these agri-tariffs first saw the light of day, losing much of their relevance in the process.

But let us start at the beginning. At the risk of stating the obvious, the UK chose to become a third country, in the EU sense of the term, used to refer to non-members of the EU. The Common European Tariff is built on this “us and them” view of the world. This detailed document was structured for this purpose and no other. The UK has adopted it with a surprisingly low number of often symbolic modifications, leaving the original EU intent intact.

It comes as a bit of surprise to learn that such humble products as dogs’ dinners command such high levels of duty. Animal foods are a downstream activity that typically draw in by-products from the manufacture of more lucrative goods. Industrialised food production brings with it a higher degree of homogenisation in both ingredients and by-products. There is a business case for ensuring that all available downstream ingredients are incorporated in some sort of secondary product, even if it only serves to dodge the cost of waste disposal. Indeed, the tipping point between a positively-priced ingredient and the operational cost of managing indeterminate mush is a crude measure of technological sophistication. That said, it will be searched for more closely in company accounts than production lines.

Working with documents generally supposedly means keeping one’s hands clean. This is a moot point, which can be illustrated with a straightforward example: tariff item 0208 40 10 is whale meat, once a common ingredient in pet foods many years ago. Third country whale meat is taxed at 6.4% ad valorem. There is a case to be made for taxing it mercilessly, on environmental grounds. There is a procedural problem with this, however, since the World Trade Organization will only cut tariffs, but not raise them. Since the WTO decisions are based on consensus, any attempt to obstruct international trade in whale meat will be systematically be blocked by Japan, Iceland and the Faroes. There are similar problems, on a smaller scale, with a 6.4% ad valorem duty on tariff item 0208 90 70: frogs’ legs.

Canned goods coming a cropper?

We have been used to seeing cheap canned foods on supermarket shelves all the year round for decades. With southern Europe just one of the many regions suffering record temperatures and drought around the world, it is timely to look at the possible impact on food products that we have relied on for centuries. It is necessary to distinguish canned foods that have an underlying seasonality, in other words, a point in the season at which the given food is plentiful.

Foods such as canned peeled plum tomatoes, canned salmon, or canned green beans, are packed during the peak cropping weeks of the season. Dedicated canning and cooking lines operate 24/7, with a scaled up version of a process that Nicolas Appert would recognise instantly. In the case of wild salmon, the canneries are located next to the rivers and are stocked up with empty cans ahead of the season. When the salmon return to spawn, fishing crews join the serried ranks of predators that are attracted by thousands of fish in breeding condition.

The standard cooking unit on such lines are a large tank of water, similar to a swimming pool, but kept at a rolling boil for the duration of the pack, which can last weeks. As the fish are caught and brought to a salmon cannery, they are prepared and the cans are filled before cooking. The duration of the cooking time is regulated by a crawler belt that covers the floor of the cooker. Small 100 gram cans are shifted through the cooker during the day at relatively rapid speeds, since they need less cooking than larger cans.

In the case of peeled plum tomato canneries, can sizes go up to 3kg. Lorryloads of raw tomatoes are delivered during the day, some of which will be kept for the night shift. When they clock in, they start filling 3kg cans while the crawler belt is slowed down to its slowest setting. By the time the day shift returns, there will be large stacks of packed and cooked 3kg cans. There will also be a steady stream of lorries laden with tomatoes for the day shift as the belt at the bottom of the cooking tank returns to its daytime setting.

This kind of production line depends on high volume intakes during a clearly-delimited number of weeks (salmon canneries generally pack more than one kind of salmon). It is vulnerable to seasonal variations and crop failures. A bit like us, really. There is an important distinction to make for peeled plum tomatoes, which is that these are mainly grown and packed in Italy. Unlike chopped tomatoes or tomato paste or passata, the cannery can only pack intact tomatoes. These are an industrial variety that are not useful for any other product.

Footnote on the protagonists in Time Travel for Food

Leadership is something we all respond to and it takes many forms.

Take a figure from history, such as Napoleon Bonaparte. A product of the ruling elite of his day, Napoleon underwent officer training and was undaunted by meeting calls to define the working structure of a post revolutionary state from scratch. The Codes Civils (sometimes referred to as the Napoleonic Codes) were an object lesson in structuring the edifice of a state at the start of a post-royal era ( Bonaparte had the outward signs of a civic visionary and expected to lead from the front.

Employing a completely different set of skills, Nicolas Appert perfected the system of sealing food into bottles or cans and cooking it so thoroughly that the product would keep indefinitely. Sometimes referred to eponymously as Appertisation, the process has been used with very few changes, for more than two hundred years. Appert predated fellow Frenchman Louis Pasteur by just over 60 years and would not have predicted the link between heat treatment and killing pathogens that Pasteur would make in years to come.(

There are grounds to suppose that the Appertisation process was known to food producers, but not widely practiced in the 1790s. In place of a theoretical explanation for the incontrovertable success of the process, Appert constantly ran tests on batches of food, using bottles and stoppers of all sorts of material: ceramic, glass and metal. As the years progressed, his confidence in the process grew, as he learnt what cooking times different foods needed in a water jacket of boiling water. Nicolas Appert had been raised by an inn keeper working in Chalons-sur-Saone and was a competent chef. His entire working life was focussed on feeding people and by the 1790s Appert was working as a confiseur in a Paris suburb.

A confiseur is someone who cooks off food, usually with boiling water, to make range of “confits” or foods almost cooked to a mush. Confiserie refers to boiled sugar confectionery, while confits are table-ready dishes which can be sweet or savoury and typically capped off with a layer of fat. The aim is to cook off seasonal gluts, although meat-based confits had short shelf lives, since the melted grease did not offer any real protection to the dish. This was the reason for Appert’s interest in sealing his wide-necked bottles, in a bid to extend shelf life. Appert successfully got reliable results, which is why Appertisation is referred to as “Time Travel For Food” on this website.

Appert plied his trade as a confiseur and wholesale grocery from a workshop in rue des Lombards. He was a member of the militant Section des Lombards, who mobilised at moments of crisis during the revolution in Paris. An active Jacobin, Nicolas and his wife Elisabeth supported the revolutionary cause in practical ways, such as holding planning meetings in the workshop.

As readers will learn in the short history of Nicolas Appert, the confiseur was pulled into the Jacobin Terreur, saved only by the fact that Robespierre was executed 36 hours before Appert was due to go to the scaffold. The Appert household survive the latter years of the revolution: Nicolas is awarded an “encouragement” of 12,000 gold coins by Napoleon. This comes with a requirement to publish a manual to Appertisation at his own expense. Appert remained politically active during his life and was elected mayor of Ivry-sur-Seine.

Appert also makes a trip to England in 1814, at the height of the Napoleonic wars. The reason for the trip was for after-sales support for an English engineer who had licenced the process for commercial exploitation. The technology transfer had been overseen by Pierre Durand, a Bordeaux wine merchant turned intellectual property agent. Durand’s leadership style was simply blunt and overbearing. He met his match, however, in Bryan Donkin, his English client.

A highly regarded engineer, Donkin had undertaken  work for the Fourdrinier brothers, Henri and Seely, to make their purchase of a design for a papermaking machine work in a paper mill environment. As his French clients faced bankruptcy and Donkin still had a workshop to keep in production, there was a pause in proceedings during which Donkin tried to stake a claim on what is known today as the Fourdrinier papermaking machine. Resourceful as ever, Donkin contrived to settle the name of the machine on the brothers, but retained control over the crucial detail that allowed him to  sell working papermaking machines in his own name. Since he installed almost 200 machines across Europe, one can suppose that he was commercially successful. It should be added that Donkin also patented the dip pen and a number of nib designs, which generated far greater sales than could be earned from selling a papermaking machine. This management style is close to opportunistic, but shows a high level of resourceful thinking. Bryan Donkin’s grandson, called Bryan after his grandfather, developed and patented the Donkin gas valve, which is more widely known than Donkin senior’s achievements.

Packing them in

An unmistakeable sign of the impending holiday season turned up this morning in the form of an email from Thierry Jourdan, boss of the family-run cannery La Quiberonnaise in Britanny. Founded in 1921 by Thierry’s grandfather, the fish canning business packs sardines and mackerel landed by local inshore boats as well as taking in yellowfin tuna to pack a range of cans in domestic sizes.

Such canneries were a common sight in seaside towns during the first half of the twentieth century. Today, there are still a number of survivors in what used to be a crowded market. As the fleets dispersed and catches waned, the importance of the tourist trade was recognised by canneries along the French coast. The 1930s saw the establishment of paid summer holidays for French workers: it was the salvation of resourceful canners.

They greeted holidaymakers with open arms and tasteful souvenirs. Local artists are still engaged to create designs for annual editions of elaborately decorated cans of fish, with the promise of a fresh series the next year. Themes range from gently humorous picture postcard subjects to classical offerings that are as likely to end up in an art gallery as a kitchen. Canned fish as an art form has some unexpectedly well-known devotees. Food critic Jean-Luc Petitrenaud always takes a decorated can of sardines for his host whenever he is invited to dinner.

Investigating hydrogen

For the past eighty years scientists have been rolling up their sleeves at the Glensaugh research farm and finding robust answers to the problems facing the agricultural sector. Perched on the east coast of Scotland not far from Aberdeen, the site is set to become a carbon neutral farming environment once its building programme comes on stream, pencilled in for 2025.

BBC journalist Nancy Nicolson visited Glensaugh for an edition of On Your Farm, which aired on April 30 and is still available on BBC Sounds. Water is the key to the project, using an industrial scale electrolyser to generate hydrogen that will power tractors and heavy machinery. This will in turn be powered by an array of green energy sources, such as turbines and solar panels.

A headline figure for the project is four million pounds: this is explained in part by the additional cost of being early adopters of technology that is still in development. This project will cast a light on the current operational energy needs of a one thousand hectare estate. Investment on this scale in one agricultural location is based on the assumption that the rest of the national economy will still be functioning in the future, in a recognisable form. We are still a long way from converting urban centres into sustainable economic entities.

Listen to Nancy Nicolson here:

Scale of sugar’s cornerstone role

Modern sugar farming is potentially as bad for the planet as the food ingredient is for us. Take for example British Sugar, which buys in 8 million tonnes of sugar beet a  year and turns them into 1.2 million tonnes of sugar.

Ever since 1996, British Sugar has been developing a profitable business from a sugar beet by-product, namely the soil adhering to sugar beet arriving at the factory gate. British Sugar’s product range is marketed under the TOPSOIL brand and is sold by the lorryload to golf clubs, housing developments, parks and gardens.

pic: British Sugar

Some 3,000 farmers across the east of the UK are literally giving away their futures with every trailer load of muddy sugar beet. Nobody at British Sugar has any particular reason to worry. But the fact remains that the farmers concerned are losing 200,000 tonnes of soil a year from their core business — about 66 tonnes each per year as an average. If British Sugar was experiencing a comparable threat to its core business, it would probably respond differently.

British Sugar is the UK arm of the much larger AB Sugar group, which employs 35,000 staff at 27 locations around the world, including a Chinese sugar beet joint venture. The AB Sugar parent company is Associated British Foods, which supplies food manufacturers and retailers with an extensive range of ingredients and finished food products. ABF is the second largest processor of sugar and baker’s yeast in the world, as well as having a significant presence  in emulsifiers and stabilisers. Once a significant food retailer, its retail arm is now limited to the fashion chain Primark. This deliberate choice of non-food, avoids cannibalising the core food businesses.

Created with The GIMP

The roots of ABF go back to 1935, when Canadian Garfield Weston founded Food Investments ltd, which just weeks later became Allied Bakeries. It grew steadily through the war years and by 1956 had bought up 10 regional and national bakeries, selling 20 million biscuits a day in addition to bread.

In 2022, group profits were GBP 1.4 billion on a group revenue of GBP 17 billion. Now owned by Wittington Investments, ABF dominates the UK food sector with leading positions in key food ingredients and processes.

A good read

William Sitwell’s book Eggs or Anarchy tells of the logistical struggle to feed the UK during the second world war. Its quality lies in the author’s insight into the interplay of power, politics and military muscle. Verging on understatement, Sitwell’s account of a gargantuan effort to achieve the almost impossible.

Among the illustrations that appear is a map of the world showing the sea routes taken by different wartime food imports, listing the distance travelled by each  commodity. The map once hung in the Minister of Food’s office and carried a stern warning about not wasting food that had travelled so far and was part of the war effort.

A seasoned business man, Frederick Marquis was elevated to the House of Lords, taking the title Lord Woolton. He was appointed food minister by Neville Chamberlain. Retained by Winston Churchill, Woolton worked tirelessly to overcome the ever steeper challenges that he faced in office. His lack of experience in political life was both a hindrance and a blessing in disguise, giving him the freedom to pursue policy targets without compromising political goodwill.

Woolton demonstrates the complexity of real world logistics and how political considerations can deflect attention from operational necessities.

Piece of cake

The opening of the Paris – Cherbourg railway in 1846 gave a decisive boost to the development of a group of cake and biscuit factories in Caen. With easy access to Paris Saint Lazare, the rest of the French network was available for the onward shipping of perishable goods  in a timely manner. From Cherbourg, orders could be forwarded to the Channel Islands and ports such as Weymouth on the south coast of England.

By the end of the 19th century, the scene had been set for biscuit maker Lucien Jeannette to buy out his two partners and develop the multi-site business.  The company did not adopt the  Jeannette name until 1927.

Its branding was  founded on the quality  of its regional ingredients, namely Isigny butter and Normandy eggs. Many years later, in the 1960s, the use of cheaper ingredients wreaked havoc with the brand’s standing at the time and was remedied by restoring the original premium line-up.

Operating today with two dozen staff, the firm now sells online from