Special Report Cooking Up Better Ways to Heat This ancient universal in food processing can be done better, faster, cheaper Heating Methods for Ultra-High Temperature Pasteurization, p.3 Bring on the Heat! p.7 New Places to Look for Energy Savings, p.12 5102003_IcedTeaAd.final 12/12/02 4:22 PM Page 1 This iced-tea has a secret ingredient... A new hand cultivated black pekoe from the Himalayas? A mineral enriched spring water from the Alps? Coloring agent? No, no, and no. Incredibly, it’s the exact same bottled tea it’s been for years.The brand they ask for by name. Its secret? It now costs less to make. That’s right! Simply changing the process by which the tea is heated from the traditional batch method to in-line direct steam injection (DSI) saves time, energy and maintenance costs without sacrificing one delicious drop of quality...or changing ingredients. So now, when faced with the seemingly insurmount- able challenge of making the same product for less – from jellies to stews to baby foods to salsas – know that it can be done. Pick Sanitary DSI systems. Now you’re cooking for less. West Bend,WI 53095 800.233.9030 or 262.338.1191 E-mail: [email protected] www.pickheaters.com 2 Heating Methods for Ultra-High Temperature Pasteurization By Michael Campbell THE MOVE is on for ultra-high temperature • Foods with small particulates like baby food, (UHT) pasteurization, which will extend the soups, sauces, and stews. shelf life of milk and other dairy products. UHT • Soy based products in order to inactivate bacteria pasteurization is being used because consumers are and reduce off flavors. buying more dairy products in bulk, dairy opera- The traditional problems or difficulties in using a tions are becoming larger, and population expansion UHT process have been: is increasingly causing consumers to be located in • Sterility: The complexity of the equipment re- more remote locations throughout the world. quires more highly skilled operators to maintain Traditionally, milk is pasteurized at 180- sterility through out the aseptic process. 185°F (about 85°C) and refrigerated. Other dairy • Particulate Size: With larger particulates comes products are commercially sterilized by subjecting the danger of overcooking of the product sur- product to temperatures in excess of 100˚C, and face. then packaging it in airtight containers. The basis • Product Quality: Heat stable lipases or proteases of UHT is sterilization of the product before pack- can lead to flavor deterioration. In a number aging, then packaging it in pre-sterilized containers of cases flavor deterioration has caused a more in a sterile atmosphere. Processing dairy products in pronounced cooked flavor for UHT milk as an this manner, using temperatures exceeding 135˚C, example. permits a reduction in the required hold time to A major consumer complaint about UHT 2-to-5 seconds, and yields a shelf stable product products has always been the so-called unpleasant that can be stored for extended period of time at “cooked” taste and sometimes-brown color of the ambient temperature. finished product. This is understandable when we Some examples of food products processed under remember that dairy products in general, and specifi- UHT conditions are: cally milk, are a colloidal mixture of water, lipids, • Liquids such as milk, juices, yogurts, cream, and carbohydrates, and proteins. When the mixture is salad dressings. heated under pressure to ultra-high temperatures, 3 the protein structure is altered in such a way that Current UHT COOKING MethODS some of the proteins are denatured and off flavors or INDIrect HEATING browning can occur. With this method the heating medium and prod- The conventional method for heating products uct are not in direct contact with each other. As to ultra-high temperatures has been to use indirect mentioned earlier, the types of heat exchangers are heating such as 1) plate and frame heat exchangers, plate and frame, tubular, and scraped surface. The 2) tubular-type heat exchangers such as shell and advantage of using these types of exchangers is that tube, or 3) scraped surface heat exchangers. The you do not need culinary steam since the two media other current method for UHT production is steam are kept separate. However, each type of exchanger infusion. has its own disadvantages. The goal of the equipment manufacturer today • Plate and Frame Exchangers: While they are is not only to design equipment that can process typically easy to inspect and take up less floor product at increased product flow rates (over 35,000 space than other types of indirect exchangers, liters per hour), operate continuously for more than they are limited by gasket temperatures and 20-hours a day, and be easily inspected and cleaned, pressures. In most cases the EPDM gasket but also to design equipment that can minimize off is limited to a maximum 160˚C. The plates, flavors and browning. while easy to take apart, can over time become This is one Salsa move they wouldn’t have taught you in class Pick Sanitary Direct Steam Injection systems may not have been around long enough to make the class syllabus, but we’re more than happy to give you a quick lesson in our revolutionary, cost-saving cooking technology. Pick Sanitary Heaters provide in-line cooking for a wide variety of food slurries, including those containing bite-size pieces,like salsa.It’s a remarkable alternative to batch cooking. Continuous cooking with a Pick is more efficient, cost-effective and maintains product quality and consistency. Now you’re cooking for less. 4 fatigued as they flex from the constant high chamber and is fed forward via a timing pump. temperature steam and lower temperature Product temperature is generally controlled by product passing over the contact surface. Liq- pressure. Additional holding time is accomplished uid velocities are usually lower for a plate and through the use of hold tubes, plate and frame frame exchanger arrangement and as such can exchangers or tubular exchangers. This is followed by lead to uneven heating and potential burn-on flash cooling in a vacuum chamber where all added and browning. moisture is removed as needed. • Tubular Exchangers: While they have fewer Variations of this method involve 1) pre-heating seals and therefore do not suffer as much from gas- the product to a desired set point before the addition ket limitations or plate fatigue, they typically take of direct contact steam, or 2) using the steam infusion up more floor space and are not easy to inspect. method first followed by flash steam removal and Heating may be more uniform, however browning perhaps reheating to a uniform set point. or burn-on is possible because of the large surface All of these steam infusion methods accomplish area required to achieve the desired set point. the same thing: • Scraped Surface Exchangers: This type of ex- • Instantaneous heating and rapid cooling. changer forces product through a jacketed tube in • Lack of overheating or burn-on. which a set of rotating blades is constantly moving • Heating of low and high viscosity products. product from the outer walls toward the center. • Use of variable product flow rates. The product is more evenly heated and there is less The negatives of steam infusion are: opportunity for product browning or burn-on. • Size: The infusion chambers take up a sizeable Scraped surface exchangers are also more suitable amount of useable production floor space. for highly viscous products and products contain- • Sanitation: These systems are not easily cleaned. ing particulates. A general negative has always • Capital Outlay: Units require high, initial been the time and cost required for inspection and capital investment. maintenance of this equipment. • Operations: A fairly skilled work force is A final point concerning indirect heat exchangers required to monitor pressures, feed pump flow is that while they do a good job of heating product rates, etc. at a fixed liquid flow rate, they suffer when the liquid • Need for a Timing Pump: Added equipment side flow rate varies. The potential for burning -in and operating cost. creases as the liquid flow rate decreases. DIrect SteAM INJectION SteAM INFusION MOre thAN A VIAble AlternATIVE The general concept is to take the liquid product Like steam infusion, Direct Steam Injection uses stream and have it pumped at a higher pressure culinary steam to quickly heat a food product to the through a distribution nozzle into a chamber filled desired UHT temperature. Direct Steam Injection with slightly lower pressure, culinary quality steam. blends the liquid stream with the higher pressure This system is characterized by cascading a small steam using multiple orifice injectors, static mix- volume of product through a large steam cham- ers or venturi type injectors. The key is to get the ber. The product then collects at the bottom of the product to quickly absorb all the steam energy and 5 elevate its temperature as quickly as possible. Unlike can be minimized or eliminated by preheating steam infusion it does not require a large chamber filled upstream of the steam injector. with steam with a higher pressure liquid cascading • Sanitation: Current 3A standards call for COP through it to achieve the quick heat transfer of steam on steam injector systems so a backup unit or and liquid. removable spool piece should be considered. The immediate advantage of this type of mixing is that the mixing chamber isn’t much bigger than Test Results the liquid transfer piping. The overall assembly has a One manufacturer of Direct Steam Injection sys- minimal foot print and the mixing chamber itself is tems and an early pioneer in Sanitary Direct Steam especially small and easy to clean or inspect.