Enzymes can contribute to the development of nutrient

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Nortura Hærland, in south-eastern Norway, processes up to 100,000 chickens every single day. This results in many packets 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.

Experts at Bioco, Nofima, Norilia, Nortura, and SINTEF are collaborating to better utilise these rest raw materials. 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 takes place right next door to Nortura's chicken slaughterhouse in Hærland. This company is called Bioco. It 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.

The composition of rest raw materials may vary. 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. The producers need to be aware of the differences and know what type of process is required to achieve a consistent quality.

That is why the researchers 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," senior engineer Katinka Dankel at Nofima says.

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.

NIR (near-infrared) spectroscopy is a technique in which light is transmitted through a food sample to measure the amount of light absorbed at different wavelengths. This measurement method can quickly assess various properties of food, such as fat, water, protein, carbohydrates, and pigments.

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.

The body needs peptides to build proteins. Peptides consist of chains of amino acids. They serve as building blocks in all living cells and play a significant role in growth and tissue repair within the body.

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," Nofima senior scientist Nils Kristian Afseth says.

The water-soluble proteins obtained from the process are called a hydrolysate. It is a substance that primarily ontains 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," Nofima senior scientist and data analyst Ingrid Måge says.

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.

There is a major test that will run over several weeks underway. 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 from Bioca or Nofima 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 several times every day, around the clock. During some periods it may be as frequent as every ten minutes.

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). By utilising this infrared radiation, researchers can identify molecules. The radiation creates specific vibrations in the chemical bonds between molecules.

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. This is one of the goals of Bijay Kafle's doctoral thesis.

After spray drying, the hydrolysate becomes a protein powder. Achieving a neutral tasta has been challenging.

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 conducting a series of their own assessments of the quality of the protein powder using a rating scale from 1 to 9, where 7 to 9 represents good quality.

There are major differences between how the various enzymes affect the hydrolysis process. In the tests that are currently underway, the hydrolysis process is run under the same process conditions regardless of which enzyme is used.

For the experts at both Bioco and Nofima, the tests provide good opportunities to obtain new knowledge.

"We learn how different enzymes work in terms of yield percentage, taste, and process conditions. The next step will be to analyse what will be optimal process conditions for the enzymes we choose to proceed with. For example, this might include extending the hydrolysis process," Jonathan Fjällman, the operations manager at Bioco, says.

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