Nils Norén, David Arnold / August 2009
Science meets art on the new frontiers of freezing. Futurists David Arnold and Nils Norén, leaders of the kitchen and mixology vanguard, chart the icy terrain.
We have been conditioned to think that fresh is best, but that isn't always the case. Best is best, and sometimes, best is frozen. We're long past the days when freezing was reserved for second quality products intended only for value-oriented customers. A new group of products can claim high-quality because they are frozen, not in spite of it. We'll look at fish, foie gras, and a few more.
Sushi- or sashimi-grade fish has the highest consumer quality perception. Few consumers know that, with the exception of tuna, all fish sold to be consumed as sushi or sashimi in this country must be frozen prior to serving, per Food and Drug Administration regulations. Although freezing doesn't kill bacteria, it does kill parasites. There are no standard criteria for sushi-grade except freezing.
Unless you have access to day boat fish, most of the fish you consume "fresh" is actually fairly old. Modern freezing techniques allow fish to be frozen rapidly on the boat, halting deterioration and producing a product better than would be possible without freezing--especially true for deep water fish difficult to obtain from day boats.
The highest quality frozen fish is super frozen, a process typically reserved for expensive fish like tuna. Regular freezing at –18°C (0°F) leaves some liquid water in the fish (we'll learn more about this later). Super freezing uses temperatures around –60°C (– 76°F) so that all the water in the fish is frozen. At this temperature, called the eutectic point, all enzymatic and internal oxidative changes grind to a complete halt. The fish is essentially in suspended animation. Because the freezing is accomplished very quickly, the ice crystals are extremely small, making drip-loss low. Super frozen fish don't degrade in storage, so they don't require environmentally unfriendly and costly air shipping and can be sourced at the same price and quality year-round. Uoriki Fresh, a super frozen purveyor, freezes fish on the boat minutes after being caught. The freezing is so fast and so complete you need to wait several hours between defrosting and serving to allow the fish to go through rigor mortis. All of Uoriki's fish is pre-cut into zero-waste pieces, so you can use everything you buy. Other super frozen purveyors include True World Foods (they also have high-quality unfrozen tuna and other hard-to-find premium seafood) and ColdWave Systems.
Mark Ladner of Del Posto in New York City participates in an unusual fish-freezing program. He, like most chefs who serve seafood, knows that the endangered wild blue fin tuna shouldn't be served--but he also knows that it tastes great. Farmed blue fin tuna is not a harmless substitute: it's typically young wild-caught tuna raised in densely populated, polluting pens. Kinki University in Japan has tried to develop a sustainable alternative, which they've dubbed "Kindai tuna." Their tuna are hatched in a lab and raised in low-density enclosures, where they're hand-fed to reduce overfeeding, waste, and pollution. They're harvested after around 3 1/2 years at a weight of about 200 pounds. As you might expect, they cost a lot of money, and only a few are brought into the United States. Ladner says they're worth the price. His fish is rushed to the restaurant, where he butchers it the way he likes it: pieces cut into portions, scrapings reserved for tartare, the head reserved for Kindai testum, and so on. The minute he's done, Sona Inc., which brings in the Kindai, retrieves the fish, super freezes it, and stores it for him. Sona sends Ladner a detailed, photographically illustrated inventory from which he orders as needed.
FOIE GRAS & MORE
United States regulations prohibit hot evisceration, the process of removing the livers of animals directly after slaughter. As the duck or goose cools down, the liver starts to deteriorate and undergoes enzymatic changes. Canadian foie gras producers have no such restrictions, so Rougié, with operations in both France and Canada, eviscerates birds within minutes of slaughter. "Time is the enemy of foie gras," says Lisa Petrucco, of Rougié.
After removal, the liver is immediately deveined and put in a liquid nitrogen tunnel freezer that takes it from 100°F to –55°F in a mere 20 minutes. Whole lobes are then vacuum-packed, and slices are packed in an inert atmosphere to prevent oxidation. This rapid freezing means small crystals. Small crystals mean less disruption of cell membranes and therefore less fat leakage during cooking, which Petrucco says translates into an impressive 95 percent yield. The benefits of hot evisceration and rapid freezing don't come with an additional cost; Rougié's prices are comparable to those of other suppliers. And though they process six million geese and 12 million ducks annually, Rougié sources primarily from small husband-and-wife farming teams with flocks under 600.
In addition to products that are literally better frozen than fresh are a whole host of high-quality products that are only feasible because of freezing. Here are two that turn the idea that frozen is second best on its head.
Sweet Street Desserts of Reading, Pennsylvania, makes a huge range of upscale desserts that are shipped to foodservice establishments throughout the country. Sweet Street's focus is on quality. Taste, appearance, and service are their mantras. Sweet Street founder Sandy Solmon explains why her business model would be impossible without freezing. "Taste, texture, color, bacterial counts, production time, and energy costs all are affected by how well the freezing system does its job. A large part of our success comes from understanding the relationship between our complicated formulations and the freezing technology. Nitrogen freezing has had a big impact, allowing us
to develop some very sophisticated products that we believe will set the gold standard for any products that come straight out of the oven."
Ciao Imports of Miami Beach wanted to be able to distribute authentic Italian, fresh, artisanal pasta in the United States. The only way to do that is by freezing. But regular freezing wasn't adequate, so Ciao turned to Surgital, an Italian company with four generations of pasta makers under its belt, to produce the Laboratorio Tortellini line of fresh pasta. Laboratorio Tortellini pasta is steam pasteurized and individually quick-frozen (IQF) in a blast-chilling tunnel. IQF products maintain their quality, are easy to portion, and are cooked direct from frozen with very quick cook-times. "We were blown away by how Surgital produced their products with the highest quality ingredients and locked in that quality with their freezing techniques, says Randall Rubin, vice president of sales. "The texture and taste are phenomenal. Chefs try this product and get hooked."
Freezing food is an excellent means of preservation, but it doesn't reliably kill bacteria, nor does it denature enzymes. Freezing halts bacterial growth, but, as food is thawed, spoilage picks up again where it left off. For this reason, you shouldn't wait until just before something spoils to freeze it. Food to be frozen should be frozen as early and rapidly as possible to keep it in top condition.
Food doesn't freeze the way water does; it freezes like a solution. Anything dissolved in water has a lower freezing point than pure water. As food starts to freeze, pure ice crystals are formed, usually on the outside--not the inside--of plant and animal cells. Only very rapid freezing produces ice crystals inside cells. The liquid left in the product becomes more concentrated, lowering the freezing point. This means there is often liquid water inside food even when it feels frozen solid. The presence of water means that reactions, including enzymatic and oxidative reactions, still take place, typically at a slower rate than if unfrozen, but not static. Lower temperatures have less available water and are more stable. At –18°C (0°F) most water in most food is frozen, so it's a good benchmark for maximum freezer temperature.
Back to an earlier point: freezing tends to pull water out of cells into extra-cellular crystals. In essence, freezing dehydrates food. When it thaws, the food has to reabsorb the water or leaking (drip-loss) occurs. For various reasons, the longer something is frozen, the less able it is to reabsorb its fluid and the more drip-loss occurs.
The slower something freezes, the bigger the ice crystals will be. Fast freezing makes lots of tiny ice crystals. Tiny ice crystals are less damaging than large ones. Large crystals puncture cell membranes and cause drip-loss as well as releasing enzymes that allow slow but steady deterioration. This is why blast-freezing is better than slow freezing in a conventional freezer.
As temperature in a freezer fluctuates, product deteriorates. When the temperature goes up, some of the frozen water in food melts (remember: frozen food isn't frozen all the way). When the temperature goes back down again, that water refreezes, not by forming a new small crystal but by making the crystals already in the food bigger. This is bad. How do you prevent fluctuation? Don't overload a freezer with unfrozen or warm products. Better yet, freeze products in a blast freezer before placing them in
the freezer. Consider having one freezer for everyday use and a separate one dedicated to pre-frozen goods destined for longer term freezing.
Always tightly wrap products before freezing. Unwrapped products will suffer from freezer burn, an unfortunate process caused by water evaporating (sublimating) off the food's surface in the freezer's extremely dry environment. This surface becomes permanently dehydrated and takes on a bad flavor. Loosely wrapped food will form ice crystals on the surface, formed when water inside the food melts and re-crystallizes on the outside. Consider vacuum packing frozen items or at least using an oxygen barrier film, like freezer bags, to wrap food. Bagging food will also help prevent oxidation, especially critical for fatty foods like pork or oily fish, whose unsaturated fats are prone to oxidation. Note that normal plastic wrap is a poor oxygen barrier and is therefore ineffective in stopping oxidation.
Vegetables that tend to discolor should be blanched before freezing. Remember that enzymes aren't destroyed by freezing. When cell walls are punctured by ice crystals, the enzymes are released to do their dirty work and products can discolor.
Bread and pastries should be frozen quickly. The industry rule of thumb is that a typical slow freezing process ages a loaf of bread by a day. Bread becomes stale most rapidly at refrigeration temperatures, much faster than at room temperature. The amount of time that the bread stays at cold temperatures prior to freezing accelerates the staling. On the other hand, bread that has already been frozen tends to stale slower than bread that has never been frozen. So if you freeze rapidly and thaw rapidly, baked goods can stay in top condition.
ICE & ICE MACHINES
"Ice programs" are a serious bar movement. High-end bartenders are finicky about ice, and many have a deep mistrust of any standard ice machine other than the universally revered Scotsman nugget machine, which bartenders love for particular types of drinks, like cobblers, etc. They don't like cubes that are too small (because they can dilute drinks in a rocks glass) or have the wrong shape. They yearn for what they see as the lost age of great ice. Prior to the widespread use of mechanical freezing, giant blocks of ice were harvested from lakes and ponds in winter and stored in icehouses for year-round use. Boston was the epicenter of the ice trade, where ice was shipped over the world, as far as India (see the entertaining but sadly out of print book The Frozen Water Trade by Gavin Weightman).
Lake ice is absolutely clear. Ice crystals reject impurities like minerals and air and stay clear as long as the air and impurities aren't trapped inside as the ice freezes. Lake ice is formed layer by layer, never trapping impurities. Bartenders like clear ice because it looks fantastic and doesn't shatter when shaken the way that cloudy ice does. Since no one harvests lake ice anymore, bartenders turn to these solutions in addition to Scotsman.
Kold-Draft. Though Kold-Draft was one of the first makers of automatic ice machines, they remained relatively obscure until recently, when a host of bartenders adopted their machines. Kold-Draft cubes are big, a full 1 1/4 inches square. They look good, are clearer than other commercial ice, and melt slower than smaller cubes. For a few years bartenders had a love-hate relationship with their Kold-Draft machines, which were temperamental and difficult to service. With the increasing popularity of the machine, the company has rectified these problems. Alex Day, drinkmaster of the Franklin Mortgage and Investment Company, a new high–end bar in Philadelphia, says, "The ice's versatility is its greatest commodity. Yeah, you can make a stirred drink with any type of ice, but with Kold-Draft I get excellent control over speed of dilution--cracking a few cubes for greater surface area and faster dilution if I need a drink up quickly, or keeping the cubes whole if I need to prepare other drinks and let the ice cool the drink for a while on its own. Likewise, Kold-Draft gives me ice that I can use to serve cocktails without worrying too much about dilution. An ‘on the rocks' cocktail stays cold without getting all watery."
Manitowoc. Manitowoc's current lineup has a primary focus on quiet operation. If your ice machine will be close to your customers, you don't want it droning away destroying the ambience. The new Quiet-cube models are designed to be the most silent machines you can buy. Manitowoc has also been focusing on energy efficiency, sanitation, and serviceability. The entire water system can be purged and cleaned in 24 minutes by flipping a switch.
Hoshizaki. Hoshizaki has several main selling points. They produce a special crescent-shaped ice cube. The crescent-shaped cubes are supposed to minimize splashing when you pour. It is also supposed to have "superior displacement," meaning they fill a large volume of the glass, making your pours look taller on average. Their other main selling points are the simplicity of system, which minimizes downtime, and their all stainless evaporator, which stays cleaner.
Ice-O-Matic. Ice-O-Matic machines deliver Pure Ice®. The active ingredient ionic silver works 24/7 to inhibit bacteria and slime fungus growth. The company is currently emphasizing energy saving performance as well as eco-consciousness by promising to plant one tree for every ice machine they sell.
Freeze your own ice in molds. Sasha Petraske, of Milk and Honey, Little Branch, White Star, The Randolph, et al in New York City, started freezing big ice in molds in domestic chest freezers years ago. As far as he's concerned, the ice isn't perfect; it's still partly cloudy. But some of it's clear, and he can make ice for specific applications--like perfectly sized spears for his Collins drinks. Shaking ice is carved from big hunks frozen in regular 6 pans. Take note: chest freezers rarely break and are cheap.
Buy good ice. When Richie Boccato, well-known for tending bar at Milk and Honey and Little Branch, teamed up with Petraske to open Dutch Kills in Long Island City, New York, he rejected ice machines altogether and ordered 300 pound blocks of ice instead. Each block costs around $75 delivered and can be used for about 300 drinks. There's always a block on display at their ice carving station, which makes for a great show. Bartenders prepare their own ice before service, so they can make the ice most suitable to their style. "It gives them ownership," Boccato says. The Dutch Kills crew trained for five months prior to opening until Boccato was satisfied with the techniques. "We had to relearn some lost arts," he explains. He stores the ice blocks in domestic chest freezers and uses Japanese wood saws, chisels, upholstery hammers, and ice picks to break them down.
Don Lee, formerly of PDT bar in Manhattan and now with David Chang at Momofuku Ssäm bar, orders from a company that provides blocks to ice sculptors. The ice is made in Clinebell machines, which produce absolutely clear blocks that look fantastic in the glass. "Basically, I'm treating the ice as a garnish," says Lee. "It has to look beautiful. We're serving the best brown spirits. If they're going to be served on the rocks, we need the best rock. If sushi is all about the rice, a drink on the rocks is all about the rock."
Liquid Nitrogen. Liquid nitrogen is about as cold as you can get in the kitchen, registering a whopping –196°C (–321°F), and it's nondiluting and noncontaminating to boot. Despite its preposterous coldness, liquid nitrogen possesses only 15 percent more cooling power than the same amount of ice at 0°C. This counterintuitive fact leads many chefs to underestimate the amount of liquid nitrogen they need for a given task, like making ice cream.
Theoretically, ice cream made with liquid nitrogen is the best because it freezes so quickly, and the quicker the freeze, the smaller the ice crystals and the smoother the ice cream. Theoretically, because commercial ice cream machines make sufficiently small ice crystals for most palates, and because it's too easy to overfreeze portions of liquid nitrogen ice cream.
There are many other fantastic LN applications, however. You can turn fresh herbs into powder, separate citrus fruits and raspberries into jewel-like pieces, and freeze alcohol to make liquid centers. Dani García of El Calima in Marbella, Spain, famously uses liquid nitrogen to freeze olive oil. Be warned: liquid nitrogen is addictive and mesmerizing in the kitchen.
A note on safety: Nitrogen is the main component of the air we breathe. It's completely and utterly nontoxic. End of that story. The dangers of LN are cold-burns, asphyxiation, and pressure-related explosions. Be careful not to serve items to your customers too cold because you could spoil someone's meal by burning their tongue. If a small amount of liquid nitrogen touches your skin and rolls off, you will not be harmed. Lab technicians routinely dip their bare hands directly into liquid nitrogen (a layer of vapor is instantly formed, protecting fingers). The danger occurs when liquid nitrogen remains in contact with skin, whereupon liquid nitrogen burns just like hot oil (take it from us). Don't wear clothing such as cuffed pants that can capture the liquid nitrogen.
Always wear safety goggles; liquid nitrogen can boil up and into your face at any moment, quickly blinding you. A small amount of liquid nitrogen turns into a large amount of nitrogen gas. If you use a lot of liquid nitrogen in a closed space, it can displace the oxygen and suffocate you before you know what's happening. Don't ever go into an elevator with a large quantity of liquid nitrogen. In a car, open the windows. Be sensible.
Never seal liquid nitrogen in a closed container. The pressure will rise, and unless the container can hold 1,000 psi or better, it will explode. In July, a young cook in Germany was severely injured this way. Liquid nitrogen containers, called dewars, are either completely vented to the atmosphere or held at roughly 22 psi with multiple safety valves. If you use a container that's sealed or could become sealed by mistake, you are in dangerous territory.
Liquid nitrogen can be obtained from compressed gas/welding suppliers. You have two choices: buy a small dewar (10 to 50 liter capacity) and have it filled on a regular basis, or buy a large storage dewar (160 to 240 liter capacity) and have the company swap yours for a full one when you need it. The larger dewars are much more economical; they cost more initially ($2,000 versus $1,000) but are much cheaper to own. You'll pay the same amount to swap out a 160 liter dewar as you will to fill a 50 liter dewar. And if a small dewar develops a leak or breaks, it's your problem, not an issue with large dewars because they are swapped out. You can usually rent the large dewars for a small monthly fee, plus a rather large refundable deposit.
Blast chillers have been popular in Europe for quite some time but have only recently gained popularity in the United States. One theory for our late adoption is that we have much more ice on hand and thus haven't felt the need for a separate chilling appliance. Once you get one, however, you'll be hooked. Blast freezing is the fastest way to freeze something unless you have liquid nitrogen. Because it freezes quickly, the blast chiller produces small ice crystals, which leads to higher quality thawed products. If you own a Pacojet, the blast freezer is the best way to quickly freeze the Pacojet containers. In the pastry kitchen at service time, the blast chiller is phenomenal at quickly tempering ice cream and keeping it tempered. When parfreezing meats for use on a meat slicer, the blast freezer quickly takes food down to the perfect consistency, but can be set to not freeze meat rock-hard (which would damage the slicer). Blast chillers have two main functions: to quickly chill foods from cooking/holding temperatures down to safe refrigeration temperatures, and to shock-freeze foods to freeze them quickly. Blast chillers are much more effective at cooling than a typical fridge or freezer because they have large fans that blow cold air around the inside of the cabinet, creating turbulence and greatly decreasing the chilling time. They're like convection ovens for chilling. Food left in a hotel pan on the counter and then placed in the refrigerator can take longer than four hours to cool down. During that time, even if food safety isn't compromised, deterioration begins to take place. By chilling rapidly in a blast freezer, this deterioration is slowed and food stays in top quality for longer.
Typically, blast chillers have two chilling modes: soft chill, which ensures that delicate foods won't freeze on the outside during chilling, and hard chill, good for meats and casseroles, which jump-starts the chilling process with very cold temperatures and then goes up to refrigeration temperatures to prevent freezing. Some manufacturers offer hard chill–plus for a more intense hard chill. Most units can chill based on cabinet temperature or based on a probe placed in the food, using the probe to verify that food is chilled to below 40°F at the core within four hours. Some blast chiller manufacturers:
Electrolux. Electrolux's Air-O-Chill blast chillers/freezers have a new feature called cruise control, which monitors food via the internal probe and adjusts the chilling profile to match the food. Electrolux designs its blast chillers to work its combi-ovens. If your chiller is undersized, it can't cool the output from your oven in the required four-hour time window; food cooked in an Electrolux combi can be chilled properly in its matching blast chiller.
Irinox. Irinox blast chiller/shock freezers have some nifty features, like a probe that can safely penetrate vacuum bags to insure HAACP chilling times on sous-vide items and a heated probe to ease removal from frozen items (yeah, that can be a problem). They also have ultraviolet sterilization lights. Blast chillers often don't run 24/7 and can get stinky if left on with the door shut. Irinox's sterilization system assures sanitation.
Traulsen Traulsen's blast chillers are marketed on two points: durability and ease of use. They don't disappoint.
The versatile fridge/freeze combo is a new piece of refrigeration equipment entering kitchens today. These are drawers and cabinets that allow the user to operate them as either refrigerators or freezers. You can quickly customize them to suit whatever's being stored. When your menu changes, change the settings on the unit to suit. Do you have three drawers set up as refrigerators and one as a freezer but need an extra freezer for a special event? No problem: just set one of the refrigerators to freeze for a day. Here are three units:
Randell FX. Randell's drawer system is versatile and extremely energy efficient. The drawers are fitted with large insulating tubs that can accommodate two hotel pans. These insulated tubs are leak proof, easy to remove and clean, and ensure very low leakage of cold air out of the unit. When you open the drawer, the cold air stays put in the drawer. The airflow inside the unit is designed to cool efficiently without drying out food. Drawers can be set anywhere from –5°F to 40°F. The 4-N-1 unit has a thaw function and a rapid chill function to take the load off your blast chiller.
Versa Drawer. The Versa Drawer from Delfield offers undercounter drawers that can be configured like undercounter refrigeration drawers but can easily be switched between freezer, refrigerator, chiller, and thaw cabinet. Like the Randell, the chilling function is designed to safely cool food from cooking temperature to 40°F in under four hours and then revert to a holding refrigerator. Delfield's graphic control interface makes switching back and forth between the separate functions simple. Temperature range is –5°F to 41°F.
Irinox CP Multifunction Holding Cabinet. These holding cabinets are the ultimate in versatility. They can be configured to between –22°F and 60°F. In addition, you can set the humidity inside the cabinet (six levels between 45 and 95 percent relative humidity). Need low humidity at 60°F for chocolate? Fine. Need higher humidity for aging sausages? OK. Need to keep frozen foods preserved in top condition? Set to –22°F. An intriguing product.
The anti-griddle is a self-contained refrigeration unit that chills a stainless-steel plate to –30°C (–22°F). It's like a griddle top in reverse. The anti-griddle was born from a collaboration between Philip Preston of Polyscience, the immersion circulator people, and Grant Achatz of Alinea restaurant in Chicago. Achatz wanted something flat and cold without dunking a plate of metal into liquid nitrogen, and he wanted to quickly freeze liquids into disks that were crunchy and frozen on both sides but liquid in the middle. Preston, who likes to make crème anglaise lollipops, said, "Yeah, I can do that." The advantages of the anti-griddle are portability, relative low price (under $1,000), and ease of use. The anti-griddle can keep presented foods ice-cold and chill shots of liquor Cold Stone Creamery–style.
ICE CREAM MAKERS
Most pastry chefs are aware of the two standbys of the kitchen, the Taylor Model 104 batch ice cream machine and the Coldelite/Carpigiani LB-100. Both are air-cooled, 120 volt, horizontal cylinder machines with a four quart capacity; both are easy to place in a kitchen. The LB-100 seems to have a lock on higher end pastry chefs, who love the texture it produces. The Taylor is seen as a no-nonsense workhorse that can take a beating and can be repaired easily. Stoelting also produces some interesting products, including the VB-9, a small vertical batch freezer. Many ice cream experts believe vertical freezers produce better ice cream than horizontal freezers because gravity brings the denser, unfrozen product to the bottom of the cylinder, where it can freeze quickly into small crystals. Several years ago Stoelting purchased the Ross Company, known for its frozen custard machines. The Stoelting/Ross CF-101 frozen custard machine is unique among small ice cream makers because it's a continuous freezer. One measure of a machine's ability to make quality ice cream is its batch time: shorter batch times mean smaller ice crystals and better the ice cream. Continuous freezers have a long, thin barrel that continuously pumps out frozen product and has an equivalent batch time of seconds, not minutes. The CF-101 produces an extremely dense, low overrun product; it's just waiting to be adopted by a high-end chef.
The Pacojet takes an entirely different approach. The size of a large blender that plugs into a standard wall socket, it produces some of the best-textured ice cream and sorbet imaginable. Most ice cream machines rely on fast freezing to obtain small ice crystals. After the ice cream is made, it's in a constant state of decay, as ice crystals grow larger and texture deteriorates. With the Pacojet, you freeze your products rock solid in stainless-steel containers. They can stay in these containers indefinitely, because there is no texture to deteriorate. When it comes time to make the ice cream you load the canisters into the Pacojet, which feeds a small, very quickly spinning, very hard blade into the rock-solid product and shaves off ice crystals as small as those produced in the best conventional ice cream machines. Freezing takes place any time; texture is created à la minute. This is especially useful if you want to maintain a large variety of flavors but don't need tons of any one flavor at a time.