Analysing properties of various enzymes to develop top-quality protein powders

In front of the From left: Nils Kristian Afseth, Katinka Dankel, Ingrid Måge, Jonathan Fjällman og Marco Cattaldo in front of the process line for continuous enzymatic hydrolysis in tubes. Photo: Wenche Aale Hægermark, Nofima

Experts at Bioco, Nofima, Norilia, Nortura and SINTEF are collaborating to better utilise rest raw materials from chicken and turkey. The goal is to develop healthy ingredients for human consumption.

Nortura Hærland, in Inner Østfold, processes up to 100,000 chickens every single day. This results in many packs of breast fillets, thigh fillets, minced meat, thighs and breasts – and there is a lot left over. Quite a lot of meat is left on the carcass. This is called rest raw material or residual biomass and is mostly used for animal feed. The goal is to develop ingredients for human consumption because this raw material contains nutritious components that can be utilised in various foodstuffs.

The development and production of the new ingredients take place right next door to Nortura’s chicken slaughterhouse in Hærland. This company is called Bioco and is Norway’s only facility that converts chicken and turkey raw materials into high-quality ingredients. Two parallel pipes which lead from just under the roof of the slaughterhouse across the road to Bioco carry this raw material.

Large variation

The composition of rest raw materials may vary. For example, there is a difference in nutrients between rest raw materials from turkey and rest raw materials from chicken. The same is true for skin as opposed to the meat left on the carcass. In order to make products of the same quality day after day, it is important that the raw material mixtures have as consistent a quality as possible, or that one is aware of the differences and knows what type of process is required to achieve a consistent quality.

That is why the scientists have installed an NIR sensor just behind the grinder that grinds the rest raw materials into a mince. Among other things, the sensor measures the contents of fats, proteins and bones in the mixture that continuously flows past.

“In this way, we can learn more about how much the raw material actually varies, and how the variation affects the process and the final product”, says Nofima Senior Engineer Katinka Dankel.

Together with doctoral research fellows Bijay Kafle and Marco Cattaldo, she has spent many workdays at Bioco following up on the NIR measurements and collecting more data from the process and the product.

The ground raw material is mixed with water and enzymes, and then a so-called hydrolysis process takes place. This is an imitation of what happens in the body’s digestive system where enzymes break down larger protein molecules into smaller peptides and amino acids.  After about an hour, the process ends and the mixture is separated into three different fractions: fats, water-soluble proteins and a sediment rich in minerals.

“The unique thing about this process is that all the raw material is converted into valuable products – nothing is wasted. In the current tests, we are focusing on the protein part”, says Nofima Senior Scientist Nils Kristian Afseth.

Enzymes affect the taste

The water-soluble proteins obtained from the process are called a hydrolysate, and the hydrolysate mainly contains peptides and amino acids. It is important for Bioco that as much protein as possible in the raw material ends up in the hydrolysate; this produces high yields. In addition, it is important that the hydrolysate has the correct nutritional composition and tastes good. The experts are now testing different enzymes to see if and how they affect both the composition and the yield.

“The goals of the trials we are now conducting are to analyse how changes in both the raw material and the enzymes affect the hydrolysates”, says Nofima Senior Scientist and Data Analyst Ingrid Måge.

She is responsible for compiling and analysing all the data from the tests. Marco Cattaldo is also part of the data analysis team. He is a doctoral research fellow at DigiFoods and is investigating how the NIR measurements can be used to adjust the process so that the yield is high while the hydrolysate is always of the right quality.

Testing five different enzymes

There is a major test underway that is running over several weeks. Every week, a new enzyme is tested, while the process operators make controlled changes in raw materials and the addition of water. To see how the hydrolysate is affected by these changes, samples must be extracted from the process. That means someone has to put on protective gear, open a hatch in a tank, and fill a small plastic tube with steaming hot liquid. During the test weeks, this is done many times every day, around the clock, and as frequent as every ten minutes during some periods. To achieve this, both process operators from Bioco and Nofima employees have been working really hard.

The samples are taken to Nofima’s laboratory where they are thoroughly analysed using many different measurement methods to characterise both protein composition and other properties. One of the measurement methods that has proven to be well suited for measuring protein quality is Fourier-transform infrared spectroscopy (FTIR).

Transporting the samples to an external laboratory is cumbersome, so scientists from SINTEF and Nofima are working to develop a portable FTIR instrument that can be used to directly measure protein quality in the factory. An instrument like this will make it possible for the industry to control product quality quickly and easily, which is not possible today. Among other things, this is the goal of Bijay Kafle’s doctoral thesis.

Taste judges assess the taste

After spray drying, the hydrolysate becomes a protein powder, and it has been challenging to achieve a neutral taste. There are several factors that affect the taste – the enzymes, the process and the composition of raw materials. The powder can sometimes taste bitter or burnt. The goal is for the protein powder to have a neutral taste.

Protein powder from all the different batches will undergo several taste assessments by Nofima’s professional sensory judges.

The Bioco staff have visited Nofima’s sensory laboratory and received taste assessment training. They are now making a number of their own assessments, which are part of the quality assurance of the protein powder. They have developed a system in which they describe the characteristics of the different samples, giving a total grade between 1 and 9, where 7 to 9 is good.