When it comes to high-pressure processing (HPP) and the produce category, guacamole came first. HPP grew to catch on with salsas and, today more than ever, juices. Now experts say there’s even more potential with HPP for processing products made with fresh produce – with some limitations. HPP uses pressure rather than heat or chemicals to disable pathogens in foods, according to Mark Duffy, chief executive officer for Universal Pure.
Once packaged, food products go into a machine that applies a high level of water pressure – up to 87,000 psi in some cases. “High-pressure processing can deliver a ‘better’ product, in some cases, than heat pasteurization can,” said Mary-Grace C. Danao, research associate professor at the University of Nebraska-Lincoln Food Processing Center.
“In general, with HPP, shelf life is longer, vitamin/mineral/ antioxidants/pigments are not affected by pressure as they are by temperature, sauces can be infused better into a meat product, etc.” HPP could also help preserve the nutritional aspects of foods. “Many of those flavors, colors, vitamins are destroyed or reduced in the thermal processing, so they lose that benefit,” said Prem Singh, president and chief technology officer of Teeinovations, which specializes in packaging including a film designed for HPP. The advantage to HPP is that it functions as an intervention step in a way that preservatives don’t, said Joyce Longfield, vice president of product innovation for Good Foods and chairperson of the 2017-formed Cold Pressure Council. Preservatives may inhibit the growth of pathogens such as listeria, but the cells can still remain alive in the product, whereas the pressure of HPP is lethal to pathogen survival. “Preservatives are not an intervention step,” she said. “They prevent organisms from growing. “If I use a preservative like potassium sorbate to make a hummus, or a salsa … all that’s going to do is prevent listeria from growing, but it doesn’t kill it. A lot of people don’t understand that.”
Longfield cites the example of a salsa company she encountered at the recent United Fresh convention in Chicago. The company is using a plant-based preservative to achieve 120-day shelf life with traditional processing methods. Longfield argues that the slightly higher cost of HPP would be worth the tradeoff of reducing spoilage and eliminating the chance of a pathogen recall. “Right now everyone sees the dollar – that’s the first thing that comes to mind,” she said. “Preservatives are cheap, but that doesn’t give you food safety.”
The right stuff
HPP isn’t suitable for all types of produce-related products. Right now in produce, Danao said, it lends itself to fruit- and vegetable-based juices, purees and baby foods, as well as ready-to-eat avocado/guacamole, salsas, vegetable dips, sauces and salad dressings. “HPP is ideal to produce processors who want to deliver a product that is safe, has a long shelf life and doesn’t mind that it will need to be refrigerated for the entire shelf life,” Danao said. “If the intent is to make a shelf-stable product, then it will be best to stick to the traditional thermal processing technologies.” The process doesn’t lend itself to fresh produce like shredded cabbage or lettuce, said Dallas Hoover, a professor in animal and food sciences at the University of Delaware. The pressure is just too great, and the product has to be packaged.
“If it’s not cut and already minimally processed in some way that it can be packaged, it’s not going to happen,” Hoover said. “It doesn’t work well or compete well with frozen product.”
David Acheson, chief executive officer of food and beverage consultants The Acheson Group, echoed that HPP isn’t for produce that needs to remain physically intact. “It’s going to have to be a different product you can apply pressure to,” he said. Acheson said “a lot” of his clients use HPP for its risk-mitigation capabilities. “We’ll occasionally recommend HPP as an intervention that can get a company out of a pickle,” Acheson said. “We’ve done it with a manufacturer that made pesto out of fresh basil.
“They were producing it and trying to control risks, but had some challenges with listeria.” The company couldn’t cook the product because it would have changed its characteristics. HPP was the solution. “That’s one of the issues potentially with HPP over heat – the desire to maintain its natural qualities,” he said.
Limitations of HPP
HPP isn’t generally practical for processing extremely large volumes of product. “The technology is a batch process – it’s not like a continuous process,” Longfield said. “So if you think in terms of pasteurization, it’s a continuous process – it can do something like 24,000 pounds an hour. “With HPP, even using the biggest machine, you’re probably looking at most at 5,000 pounds an hour.” And the equipment is so expensive that many companies, especially those just starting out, use an HPP copacker to make their product as opposed to investing in their own. Not so at Good Foods, which started out as HPP first. Longfield said HPP came on founder and CEO Kurt Penn’s radar at a trade show around 2008. After selling a chicken sausage company he’d been operating, he was ready for another venture.
“He knew he needed HPP as his food safety source so he actually bought an HPP machine without even having a company or a product to go through it,” Longfield said. “He thought, ‘This is the future.’” Today, Good Foods produces more than 150 different products including guacamoles, yogurt dips, juices and prepared salads (chicken, quinoa and grain, for example) – all using HPP. “A lot of companies tend to make just salsa or just hummus or just guacamole and focus on one or two categories,” Longfield said. “We look at ourselves as an HPP company that makes foods. “We look at what our consumers want, the trends. We look at those products, and are they suitable for HPP, and if so, how can we start to develop those product lines.”
What’s on the outside counts
Packaging is key to the HPP process. “HPP users need to choose a packaging material that has good barrier properties to minimize oxygen and light coming into the product,” Danao said. “The packaging must also be able to withstand the high levels of pressure applied during processing, as well as pay attention to the amount of headspace in the package.” Singh said packaging can be divided into three types: trays like those that frozen meals come in; bags or pouches; and bottles and jars for juices and salsas. And it all has to be able to withstand the high pressure.
“In the beginning of HPP, a lot of failures happened because even the large companies did not understand the role of packaging in HPP,” he said. Packaging has to be able to revert back to the original shape, he explains. Singh’s company is among those that produce a film designed to function with HPP. “It seals through trays made from polypropylene or PET or the crystallized PET black trays you see in grocery stores,” Singh said. “It seals to all of those strong enough that it survives the pressure. “The seals are strong enough that they go through HPP, but the beauty is that you can still peel it.”
Expanding HPP – and awareness
Singh predicts that research and investment to explore the ways HPP can be expanded in produce-related processing will result in an expanded range of offerings in the category. “We have actually seen that you can enhance the texture by selecting the right amount of pressure and temperature,” he said. “We are beginning to understand how we can use HPP for non-liquid or non-pureed products like chunks. “It depends on the food type. Pineapple does behave differently than papaya or mango or guava … there’s more work to be done.” Consumer trends are also going to drive expansion, Danao predicts. “As more and more consumers look for high-quality plant-based foods, the more HPP technology will be applied to fruit and vegetable processing,” she said. Meanwhile, Longfield said the Cold Pressure Council was formed by HPP industry representatives to serve as a resource for startups and others who need help implementing HPP into their HACCP plans. “It’s a resource for companies working through regulatory challenges and food safety challenges,” she said. “Part of the reason is the FDA guidance documents are not written for how to apply the regulations to HPP.”
The council wants to work with regulatory bodies and be a resource to help create uniformity and consistent food safety practices among food manufacturers using HPP technology. “There’s no specific directives to tell you how to use HPP for every food category,” she said. “So what happens is across the country, you have inspectors interpreting the guidance documents and how HPP can apply to it. You don’t have any consistency.” The council is also trying to educate consumers about the process and what’s in it for them. Danao said consumers may have a general understanding of what HPP is, but remain confused “as to whether the product is truly raw or fresh, minimally processed, coldpressed, or pressure pasteurized’ or high-pressure processed.”
Companies that meet council guidelines via audit will be able to affix a logo bearing the Cold Pressure Council and high-pressure-certified resource websites. There, consumers can find out more about why HPP was chosen over pasteurization or preservatives in the production of the product “HPP products in North America totaled, I think, $12 billion in 2015, and people just don’t see it,” Longfield said. “Nobody really advertises they’re using the technology. “Part of the logo program is to start to drive consumer awareness and consumer desire.”