It’s just pressure

Thanks to Multivac’s new HPP technology, integrated high-pressure preservation is now available for MAP packed food items to extend their shelf life without heat, radiation or artificial additives. Up to 6000 bar rids the treated food of harmful microorganisms without affecting its nutritional value. Stefan Richter reports.
When Sepp Haggenmüller and his friend Artur Vetter built their first vacuum chamber machine in a garage in 1961, they named it Multivac. From these humble beginnings in Böhen, a small town in Southern Germany, the company Multivac has grown into one of the world’s leading suppliers of packaging solutions for food. 50 years later the company employs more than 3200 staff, allocated to over 60 local companies and branches around the world. In their 50th anniversary year Multivac launched an interesting innovation at Interpack 2011 in Düsseldorf, Germany, that must have made a lasting impression on the representatives of the New Zealand Food Innovation Network (NZFIN). Multivac sold its first HPP (high pressure processing) system to the FoodBowl, which is NZFIN’s Manukau-based hub, and this technology now constitutes the key part of Hall 4.
High pressure processing as such has been around for quite a while. It has been known since the end of the 19th century that high pressure, exerted on certain food items, destroys pathogenic microorganisms. The pressure interrupts various important cellular functions, resulting in the harmful organism’s inability to survive. No heat or chemical additives such as preservatives are needed to extend the food’s shelf life. What is more, at the same time sensorial properties and nutritional value, taste, texture, and appearance of the HPP-processed food are almost entirely retained. “The benefits of HPP have been known for a long time, but the technology has only recently become commercially viable,” explains Stephen Holmes, Managing Director, Multivac NZ Ltd. “And now Multivac, together with Uhde High Pressure Technologies, have further developed and refined the process. Thanks to a controlled decrease of pressure during the treatment, it is now for the first time possible to process MAP packs without loss of quality.”

HPP – the technical principal
The technical principle behind HPP does not sound very complicated. The already packed food items are placed in a loading tray and then put into a pressure chamber. This chamber is sealed, flooded with water, and pumps generate a pressure of about 6000 bar. After a certain holding time, which depends on the food item, the chamber is depressurised and the food packs can be taken out. But the devil, as so often, is found in the details. “It is not so much about how we take the pressure up to 6000 bar, but how we control it coming down again,” says Stephen Holmes, “If you release the pressure too rapidly, the gases that have been forced inside the food and the packaging material escape very rapidly, and both can suffer damage. The damage caused to the barrier layer of the packaging material can allow oxygen to penetrate the MAP pack, which reduces the product’s shelf life. The quality and appearance of the food item might also be affected by little blisters forming on the surface due to erupting gases.” That’s why it was not possible so far to treat MAP packs with HPP technology, but only vacuum-packed food items. Modified atmosphere packs have a lowered amount of oxygen, which in the packaging process is replaced by nitrogen, carbon dioxide or monoxide to slow down the growth of microbes. Ultimately, the shelf life of an item with modified atmosphere is extended and the overall presentation improved.
The new technology by Multivac and Uhde exactly monitors and controls the pressure release, a feature which Stephen Holmes calls “soft depressurisation” and which requires intimate knowledge of the mechanisms taking place under high pressure and a good grip on the technology involved. “For the first time food packs with modified atmosphere can be processed without the mentioned side effects,” says Stephen Holmes. The individual parameters for each food item and package can be stored in the machine control of the HPP system. But there was another technological obstacle to overcome to make the technology economically attractive. “Until now, the HPP process mostly had to be performed offline, separated from the packaging procedure,” says Stephen Holmes. “Most containers that are available present only a small opening at one side of the cylinder, too small for handling modules or robots to load or unload the containers. In order to integrate this process step into the packaging line we needed to come up with a solution that allows for automatic loading and unloading.”



New tray design enables automated handling
The company’s idea consisted in constructing a cylindrical tray that can be unfolded into two halves and closed again automatically, making it accessible for automated handling devices. “Customers can now process up to four tons of packed food items per hour; the new trays ensure maximum throughput and continuous product flow and significantly reduce processing costs per pack.” All these developments have already paid off, the company reports to have sold six units worldwide so far (including the one operating in Manukau’s FoodBowl). Multivac has also registered several technical solutions, such as the soft depressurisation and the innovative tray design, for a patent.
Multivac’s new HPP technology might have come at the appropriate time. Consumers worldwide are becoming more and more interested in the quality of the food they put on the table every day. Nutrients are in, preservatives and other artificial ingredients are out. HPP can provide the food industry with a sophisticated tool to produce high-quality food items without using chemical additives, radiation or heat treatment to extend shelf life. Stephen Holmes gives an example: “Orange juice that has undergone heat pasteurisation retains only 40 percent of the initial vitamin C after 20 weeks at 4˚C. After treatment with HPP, 85 percent of the vitamin C can still be found in the juice after 20 weeks at 4˚C. The cold pasteurisation process is completely natural, it’s just pressure.”
Multivac NZ was established in 2005 and has grown into a company of 13 people working in the Pukekohe and Christchurch offices. At the moment the company has a new building under construction near the airport, close to the FoodBowl. “We are well established in New Zealand, about 110 of our machines are working throughout the country. Our main customers are meat and seafood producers, dairy industry and bakeries,” reports Stephen Holmes. The managing director perceives a trend towards value-added products in the meat industry. “Instead of vacuum packing and sending whole carcasses overseas, the meat industry is starting to cut the carcasses into retail-ready portions and pack it nicely. That way producers can demand higher prices and increase their profits. In this area of value-added production there is a big market opportunity for our thermoformers.”
Another industry trend, increased automation, is somewhat inhibited by one peculiarity of the NZ market. “European food producers set up their machines once and then continually produce the same item. Here in New Zealand, there is no such mass production, the machine setup has to be changed all the time as there are so many different items to produce. Due to all the frequent changes it can be a quite challenging task to use robots,” says Stephen Holmes. But growing cost of labour, decreasing cost of technology and higher reliability make automated production increasingly attractive to companies. “And that is good for Multivac, as we are able to supply complete packaging lines including weighing and feeding systems, packaging machines with identification systems, labelling and visual quality control and package sorting systems.”

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