The customer could hardly believe their eyes when unsoaked beans as hard as rock were transformed into a hot paste within 15 minutes in a mixer. The normal industrial process takes about 24 hours and involves a number of steps and pieces of equipment. The trial took place at the Tetra Pak Product Development Centre (PDC) for mixing solutions in Aalborg, Denmark.
Refried beans consisting of mushy bean paste is a popular warm dish in the Middle East and Latin America where it is known as “mole” in Mexico, which means sauce.
Similar products have previously been processed using a Tetra Pak High Shear Mixer, however the beans were always soaked or softened beforehand. Processing of dried beans direct in the heating step had never been tried until the trial in 2016 at the PDC. The process worked surprising well in a 100-litre batch taking just 15 minutes to reduce hard beans to a smooth mash. After this demonstration and further trials, the customer was so impressed that they ordered a 5,000 tonne Tetra Pak High Shear Mixer for their factory in Guatemala. A patent is now pending for this unique process invented by Tetra Pak.
“We don’t have a time-consuming soaking phase that can take 2-12 hours,” says Hans Henrik Mortensen, Manager of the Centre of Expertise. “We take the washed beans, put them in our mixer and add a little water. Then we start grinding them down and heating them up at the same time. By combining the cooking and grinding steps, we save time. Cooking beans that have been ground into particles is much faster than cooking whole beans and this also saves time. What’s more, we can do all these steps in one machine.”
The traditional method for processing beans into paste products like refried beans consists of several steps, each of which is usually carried out in a separate, dedicated piece of equipment:
Washing → 2. Soaking → 3. Heating → 4. Grinding → 5. Mixing
The innovative process by Tetra Pak achieves the same result but in a single mixer, reducing the total time by up to 90% compared to any known commercial process. The whole installation is much simpler, no time is wasted for transporting the beans from machine to machine and less cleaning is needed.
The beans are disintegrated into approximately 1 mm pieces by rotary blades while being heated at the same time. While the small pieces are cooking, toxic lectin-type substances present in unsoaked beans are removed. Lab tests show that the finished paste is free from these toxins and the results are comparable to the traditional process where soaked beans are used. However, industrial regulations in the USA and Europe still stipulate that the soaking of beans must take place for refried beans, so this new process is not allowed in these areas unless the regulations change. Nevertheless, the main markets for refried beans are Latin America and the Middle East where these restrictions do not apply.
This Tetra Pak concept for refried beans works for different type of beans such as black beans or fava beans. There is also great potential in the making of peanut butter from dried peanuts. The Tetra Pak High Shear Mixer can be fitted with some unique circulation features that make it possible to handle a viscous product like peanut butter or bean paste without any problem.
Proof of concept tests have been carried out using a Tetra Pak High Shear Mixer equipped with a dynamic stator system, a jacket heating system and a direct steam injection system. All process steps except washing were carried out in the mixer. Here are three examples of successful tests:
Read more about the Tetra Pak High Shear Mixer for beans and spreads