Dated: 1 May 2008
NUTS PROCESSING: Bite Size, Big Business
Nuts—they come in all shapes, sizes and tastes. As demand for varieties grow, processing them well will require a firm grip on methods and technologies.
BY NEIL SILVESTER MARKETING EXECUTIVE HEAT & CONTROL AUSTRALIA
As processors look to expand their offerings with snacks that offer more health benefits, nut products have become one of the fastest growing market segments in recent years. Apart from being a healthy alternative to the trusty potato chip, nuts also offer processors versatility in the end product by allowing local cultural twists to be introduced without completely altering the universally popular appeal of a roasted nut product. These cultural twists could be the introduction of flavoring to a coating, or it could be the blending of a nut product with other snacks such as bhuja mix.
There are a number of issues pertaining to exact processing requirements and the associated equipment for a specific processing line layout, which include blanching, dry roasting, oil roasting, coating, seasoning and cooling. Where the required production and packaging capabilities reach higher capacities of over 100kg/hour, it is recommended that consideration be given to custom designed equipment.
Drying roast nuts by means of hot air usually loosens the skin. Hence, a mechanical device is used to remove the red skin. The machine used is known in the nut industry as a blancher, which should not be confused with a steam or hot water blanching process.
Oil roasting of nuts is an alternative process where nuts are submerged or covered in hot oil and fried. Various processes can take place prior to the hot processing to achieve a specific organoleptic experience (i.e., bite, mouthfeel, taste and flavor). Examples include soaking in brine solution, coating the nut, and drying. If a processor is to dry roast nuts prior to coating, then the frying process will only be required to cure the coating and fuse it to the already roasted nut.
Although there are many different coatings that can be used on a nut product, the more popular choices include wheat fl our and cassava, with cassava showing the highest expansion rate. Wheat fl our coatings do not have the same expansion properties as cassava fl our and it is usually a thinner, crisper coating.
As with most flour-coated products, achieving the desired coating thickness is a slow and exacting process. This is mostly done in batch coating pans. The process entails loading the nuts into the coating pan with a small quantity of liquid starch to "wet" the peanuts, followed by a small sprinkling of fl our. This process is continuously repeated until the desired thickness is achieved.
The coating applied does not have to be limited to a single ingredient. Some processors will use a precooked tapioca starch with various flavor additives and non-gelatinized cassava fl our as the dry coating. A product such as this will expand significantly in the frying process, and goes through a very sticky stage which requires a "free float" flume ahead of the first stage fryer. This will set the coating to the nut.
The second stage fryer completes the cooking of the raw peanut. Every fl our-coated nut product is different and it is important that one understands all the details of the process. Depending on the process, conventional immersion frying would be the safest option for coated nuts.
In some cases, very small, raw skin on peanuts is used. The flavor that the skin imparts is preferred by some markets and it also makes the coating stick to the nut better than a nut which has had the skin removed through the blanching process. It also means that second stage frying is essential with a long fry time because the nut has to be cooked through this layer of "insulation" created by the coating and the skin.
In the first stage, the coated surface is set. This prevents the products from sticking together. In the second stage, the final cooking or frying takes place. In general, the lower the moisture content and the higher the finished bulk density, the higher the output from a conventional nut fryer.
Blanching
The most common method of blanching involves the same concept as holding the peanut kernel between the thumb and forefinger of one hand, and rubbing the thumb across the peanut with just enough pressure to remove the red skin. However, the red skin adheres readily to recently shelled, raw peanut kernels. It is very difficult to fracture despite its physically thin structure. Poor performance can be expected from any attempts to blanch fresh, raw peanuts by mechanical means without proper preconditioning before the blanching process.
The preconditioning process consists of drying or “white roasting”, followed by a cooling and tempering period. The objective of the white roast is to bring the moisture content of the nut to approximately 5.5 percent. As a guideline, the temperature must be maintained below that which will result in a noticeable change in the colour of the peanut kernel. Controlled heat loosens the red skin so that it becomes more dry and brittle and is easily fractured from the nut.
This same phenomenon occurs with fully roasted peanuts that have been subjected to higher temperatures. This is necessary to darken the colour and develop the desirable rich and “nutty” flavour. The fully roasted peanut kernel consequently becomes more brittle, which greatly increases the possibility of splitting during the blanching process. For this reason, fully roasted peanuts are not recommended for whole nut blanching.
After the white roasting process, the peanuts are allowed to temper and cool to warehouse temperature before they are blanched. This allows the dried kernels to slightly shrink away from the red skin, which greatly contributes to blanching efficiency. Depending on the amount of moisture removed in the white roasting process and the ambient air conditions, the tempering and cooling time may vary from a few hours to several days.
Refrigeration has been used in hot and humid climates to reduce the time taken for the tempering process. Refrigeration is also thought to reduce the moisture content of the red skin more effectively than hot and humid ambient air conditions. A reduction in moisture helps to fracture the red skin in the blanching process, in addition to stopping the potential growth of free fatty acids.
Coating
Most producers still use manual batch coating pans where they can add small quantities of fl our. Starch is usually added first, followed by tapioca fl our to slowly build up the coating thickness. In India, a popular method involves continuously coating peanuts with besan flour, a batter and fl our made from chick peas, in what resembles a seasoning tumble drum. This is an extremely sticky substance and a full length scraper is required to remove the coating and peanuts from the inside of the drum.
The same situation applies with honey-coated nut systems. Viscous honey solution is sprayed into the in-feed end of the tumble drum, followed by the addition of a sugar and salt mix to dry the slurry at the discharge end of the drum. Most of the popular coatings used throughout Asia are typically quite thick.
Oil roasting and frying
Certain nut types, such as macadamias, need to be handled with extra care. They are expensive to produce and are more fragile that most other nut products. Macadamias also have a delicate flavour, which makes it necessary to fry them in very high quality oil, as opposed to common seed oils.
Frying time and temperature is critical as the period between what is adequately cooked and burnt is quite short. The specific cooking parameters depend on the nut variety and hence, can only be established by the processor. It is not unusual to place the fried nuts in a centrifuge immediately after frying to remove excess surface oil. Cooked nut products also need to be placed on an ambient air cooler to remove the residual heat and stop the cooking process.
Entry level processors use small, “semi-industrial” size batch fryers. These can produce macadamias at 140 deg C for about two minutes and other nuts at 180 deg C for two to three minutes. Large capacity producers will run completely automated continuous frying lines. Nut types are processed with raw material moisture contents varying from three and fi ve percent on cashews, to about eight percent on peanuts. Moisture contents of the finished product vary between two and 2.5 percent. In most cases the preferred moisture content level of the final product is about 2.5 percent as this gives the required mouth feel (crunch and bite).
Dry roasting—the oil free alternative
There appears to be a tendency for some processors to prefer dry roasting as opposed to oil roasting. The main reason for this is to reduce the oil content of the finished product. Given that most nuts have a high level of natural oil, one would question the effectiveness of dry roasting in reducing oil content. Dry roasting is also used by producers to create a product that has an appeal to certain market tastes.
Entry level processors use domestic fan-forced or semi industrial type convection ovens in a single layer stirred regularly to avoid surface burning. Temperatures vary between 110 and 180 deg C for 15 to 20 minutes, whereas larger volumes are done in custom-designed drying ovens. Heat and Control’s experience with designing these large dryers is that a fluidized bed hot air oven enhances uniform cooking.
Cooling—improve quality and shelf life
The most common cooling method found at entry level is putting a layer of nuts on oil absorbent paper and allowing it to dry by natural draft or induced draft (using fans). Cooling is not only critical to ensuring a good quality product, it also increases shelf life by reducing the amount of residual oil left on the cooked nut.
Consideration should be given to a purpose built cooling system rather than a haphazard cooling system that lacks consistent results. The ideal drying scenario is to use an ambient air cooler specifically designed for nuts.
SNACK PACKAGING: Eye candy
Filled up supermarket shelves and no lack of choices have meant that the presentation of a brand at the point of sale is becoming more important. Visual design functions as a marketing instrument and communication tool. It offers manufacturers the possibility of a unique selling position which sets them apart, yet ensures that the product belongs to a 'family brand’. Differentiation and persuasiveness are called for because the point of sale is also the point of success, where the consumer decides on the success of the brand. The window of buying time is relatively brief; the shopper decides, within these few seconds, if he or she is interested in the product on the shelf.
Optimum appeal to a consumer should be the most important criteria. But how that is to be achieved would depend on the target market, its demands and lifestyle trends, and even passing fashions. For instance, cheerful designs are best suited to sweets and jelly beans.
Packaging for snacks has much potential to surprise the customer in a positive way, for example through novel shapes, colors and designs. For products like sweets which are kept in a visible place or specialty snacks which can be given as gifts, packaging has an even bigger influence on buying decisions. Retailers and manufacturers observe that customers take a strong interest in high-grade snack products.
As the emotionalizing of a brand plays an increasingly important role, multi-sensory packaging design is often used to position the brand in different dimensions, arrest the senses of the consumer and arouse interest in the brand. First is visual perception, which has to be appealing and convincing. Second, haptic properties can persuade buyers by enticing them to pick the product off the shelf. The packaging should sit nicely in the hands and have a touch or shape that will grab attention.
Next, scents can also play a major role in buying decisions but their potential should be assessed in the context of the retail environment. If the entire snack section in the supermarket is scented, this chaos of smells would turn away consumers more than attract them. Discreet fragrances for sweet tasting snacks or attractive spice aromas emanating from the package could enhance the effect of the product on the consumer. Used well, the combination of scents with the right visual and haptic properties can create a successful product that influences the consumer’s decision to buy.
Adapted from the report "Conflicting demands on packaging" by the EHI Retail Institute in Cologne, published April 2008.
TWIN-SCREW EXTRUSIONS: Snack on Soy
Thanks to extrusion technologies, consumers can look forward to biting more of that well-loved soy ingredient.
BY PATRICE BREILLOT SALES MANAGER, ASIA PACIFIC CLEXTRAL SAS
 Soy is a much valued food ingredient because of its proteinrich composition, and nutritional and disease-preventive qualities. In recent years, as new research has emphasized the health benefi ts of soy, consumer interest in soy-based foods has grown. As a result, processors have been incorporating this versatile ingredient into more foods and in greater proportion to other ingredients. Snacks, bakery items, and breakfast cereals are soy-enriched, while beverages, dairy products and many other foods are enhanced with soy protein.
New developments in twin-screw extrusion processing technology have given snack processors yet another tool to incorporate soy into their snacks and cereal-based products. The twin-screw extruder gently cooks the soy fl our in a continuous process that protects the essential proteins, amino acids and minerals that provide health benefits such as bone strength and cancer prevention. There are many opportunities for adding soy ingredients to snacks and cerealbased products traditionally made from corn, wheat, rice, bran, and oats.
Expanded snacks
Using a twin-screw extrusion, processors can create a variety of expanded snacks—from light, crispy puffs with an open cell structure, to denser, crunchier varieties—simply by varying the ingredient mix and the processing parameters. Expanded snacks are produced at higher effi ciencies and dramatically higher capacity on twin-screw extruders, compared with single screw machines.
In this area, improvements in technology are literally reshaping the product. Advances in die and cutter designs are giving processors an entirely new set of templates for creating innovative product shapes, far from the traditional varieties of puffed balls, twists and curls. Plus, recent developments in extruder design and control allow more textures and density combinations.
In a typical expanded snack production line, dry ingredients are blended and metered into the extruder barrel simultaneously with the liquid ingredients. Homogeneous dough is created by the co-rotating action of the screws. The extrudate is subjected to heat and shear to gelatinize the starch and “cook” the product.
Finally, the positive pumping action of the screws forces the dough through the die. Expansion takes place as the steam in the extrudate fl ashes off. The product is shaped at the die by a combination of expansion, die aperture and die face cutting, or formed into strands for post-extrusion shaping and cutting. The extruded snack enters a belt dryer, which decreases the moisture content. Finally, the product enters a coating drum where it receives a liquid fl avor coating, or it may be dusted with a fl avored powder.
In addition, the twin-screw extruder can process soy crisp ingredients. With this, snack and bakery manufacturers can add the nutritional benefi ts of soy in products such as the consumer-preferred “crunchy nuggets” and “crisps” in nutrition bars, breakfast snacks, granola mixes, and specialty bakery products. Proprietary soy inclusions with a variety of attributes (size, color, density, texture) can be processed for many different products.
Co-extruded snacks
Co-extruded snacks, with crisp cereal shells and soft fi llings, delight consumers of all ages. Processors can incorporate soy fl our into sweet or savory co-extruded products, adding a healthy twist to these favorites. Pre-engineered dies let processors create many shapes such as bars, pillows, nuts, balls, long and short ovals. Fillings range from cream, jelly and fruit puree for sweetened snacks, to cheese and meat for savory products.
The co-extrusion production line starts with dry ingredient blending in a separate mixing vessel. The dry mix is fed to the extruder with the liquid ingredients. At this point, the screw flights are an open design to form an amalgamous dough. The screw flights quickly become more severe, generating mechanical heat and shear within the product. Heating and/or cooling circuits in each section of the extruder barrel precisely control processing temperatures.
Meanwhile, the soft filling is prepared and held in an agitating tank. As processing is completed, the extrudate enters the co-extrusion die, which concurrently forms and fi lls the product.
After extrusion, the malleable product is shaped and cut. A variety of fl attening units, crimping rollers, pulling belts and stamping systems accurately create the desired profi le of the co-extruded product. Next, the product may enter a belt dryer to reduce the moisture content, if required. Multi-belt drying systems are used for small products and single belt dryers for longer products. Finally, a liquid fl avor coating may be applied or the product may be enrobed in a sweet or savory coating.
Today’s consumers are increasingly munching on snack mixes and cereal fl akes in between meals. Savvy snack manufacturers can easily include soy-based fl akes to snack blends with twin-screw extrusion technology. Extruded fl akes require a fraction of the processing time and energy required for traditional fl akes, yet exhibit similar quality and fl avor profi les.
To process extruded fl akes, dry ingredients, including grits, sugar and salt, are mixed and conveyed to a preconditioner, which hydrates and heats the mixture to commence gelatinization. The partially cooked product is fed to the twin-screw extruder.
Inside the extruder, the twin rotating screws mix the extrudate, creating heat and shear to perform complete gelatinization. Malt syrup is injected directly into the extrudate through ports in the extruder barrel. Heating and/or cooling circuits in each section of the extruder barrel control processing temperatures precisely. This process forms a dense phase extrudate, which will mimic traditional grits when processed through a fl aking mill.
The fully cooked product is forced through a die, which forms continuous strands. After a short cooling period, the strands are cut into nibs. Strands may be cut into various sized nibs; therefore, the size of the fl ake is no longer dependent on the size of the grit. After cooling, the pellets are fl aked in a fl aking mill and transferred to a toasting oven. A coating may be applied to add a sweet fl avor or vitamin enrichment, followed by a fi nal pass through a belt dryercooler.
Pellet-based snacks are great marketing opportunities for snack processors, as they offer consumers the freshest snacks at the retail outlet. Snack pellets produced on twin-screw extruders offer higher throughputs and improved product quality. In addition, new ingredient combinations and cooking techniques are creating a new range of textures for third generation snacks, giving processors a marketing edge in providing exciting snacks for trend-hungry consumers.
A versatile processing tool
Consumers want it all when it comes to snack food—freshness, fl avor, variety and nutrition are musts. Snack manufacturers want processing equipment that can help them supply this dynamic market.
Twin-screw extrusion processing technology gives processors the processing power and flexibility to produce expanded snacks, filled products, inclusions, flakes, snack pellets and more, continuously on automated equipment and at high production efficiencies.
The twin-screw extruder has established itself because of quality requirements related to the processing of the final product, and process productivity and flexibility. Extrusion processing advances have enhanced product textures (defi ned by their cellular structure), and made it possible to incorporate dramatically increased percentages of protein-rich soy into products, improving their consumer appeal. With new generation twin-screw extruders and improvements in dieflow design, higher throughputs are available on smaller extruders, optimizing investment and operating costs.
Twin-screw extrusion has opened up processing opportunities. Now, products that were once impossible with a single screw extruder can be made. Single-screw extruders are the simplest and cheapest on the market. But their process functions are limited, particularly when the formulations become complex and require a high degree of mixing, or when flexibility and high quality products are desired.
Twin-screw extruders work in a different way; the inter-penetration of the screws creates a positive movement of the material although the machine is not filled. Therefore, the throughput and screw speed are independent within a certain range of variations. When the fl ow is restricted by the screw configuration (counter-thread, mixing elements, die), material accumulates upstream, creating a working section (an active area where the material is worked by shearing), which contributes to its physical and chemical transformation, and heating by viscous dissipation. When compared with single-screw processing, twin-screw technology allows more efficient mixing, heat transfer, residence time distribution, and consequently the shear-time temperature, all of which are essential in processing soy-based recipes.
Snack processors can get on the fast track to producing soy-enhanced snacks with a complete snack production line. Turnkey systems provide all equipment from start to finish—including bulk ingredient storage, dry material feeder, pre-conditioner, twin-screw extruder, former, cutter and dryer, plus all equipment interfaces. As snack processors discover the benefits of twin-screw extrusion for processing soy-based products, this versatile and flexible processing tool may well become the way of the future.
SNACK INGREDIENTS: Munch On This
Trends in ingredients for snacks, from the snack-makers themselves.
Who
Anita Benech
Marketing Manager of Alfred Wolff, based in Germany
What
Gum arabic product, trademarked 'Quick Gum'
Versatility
"A stabilizing and suspending agent, gum arabic can be used in beverages and emulsions. Its binding properties make it suitable for pastilles, gum and jelly sweets, as this gives a right consistency and chewiness to the product. Cereal bars and fruit bars also use gum arabic as a natural adhesive within the bar and on its surface. Flavor emulsions and aromatic spray powders are another area of product application, owing to the gum's encapsulating properties."
New applications
"New directions are coming from 'functional snacks'. Gum arabic is well placed to capture this market opportunity as it is a low calorie ingredient (1.5 kcal/g), contains about 85 percent natural dietary fibers and acts as a fat-reducer. Snacks with a good texture, full taste and ingredient attributes like low-cal and high-fiber are new openings for innovative manufacturers."
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Who
Roby Danon
Managing Director of Voicevale, based in London
What
Nuts, fresh and processed, in China
Best sellers
"Pistachios are tops in China, where they are literally called 'happy nut' in Mandarin. China imported about 74,000 tonnes of pistachios in shells, up from 49,000 in 2006. Almonds are next in popularity, both kernel and shell forms, and third is the hazelnut, which is mostly eaten in shells. Cashews too fast becoming popular."
How they are eaten
"Nuts are mostly eaten in shell. They are mostly roasted, slightly cracked and slated in the south and south throughout the country. Both shell and kernels are seeing quick demand growth. Additionally, dried cranberries are popular especially in mooncakes during the Mid-Autumn Festival. We are also trying to encourage them as snacks as part of a packaged nut mix. We see many different types of mixes already available in the European markets."
Supply markets
"Mainly California for almonds, hazelnuts and pistachios. Turkey also for hazelnuts and Iran for some pistachios. Cashews come mainly from Vietnam."
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