Evaluation and optimization of the production process of carrot juice concentrate to obtain a product with a higher content of beta-carotene

Abstract

Carrot juice concentrate (CJC) produced from fresh carrots is used in various applications in the beverage industry. Its quality is mainly defined by the carotenoid concentration which in turn strongly depends on the quality of the raw material and the processing technique. Manufacturers are constantly searching for new ways to produce a high-colour CJC. Thermal, enzymatic and mechanical treatments are suitable to improve the release of intercellular, hydrophobic carotenoids into the juice phase by inducing cell wall degradation and cell rupture.

However, the complex relations between carotenoid yield, juice yield and Brix as well as the cost-benefit-ratio of such treatments are mostly not considered. The aim of the project is to evaluate and optimize the production process of CJC. Comparison of enzymatic and mechanical treatments of carrot pomace in terms of their capability to increase the carotenoid yield, while simultaneously providing a high concentration factor for colour from juice to concentrate, was the main focus of the experiments. The trials were performed on pilot-plant scale, analyses included juice yield, Brix and carotenoid concentration.

Both treatments increased the carotenoid content in the juice, but to different extents. If not only the absolute colour concentration, but also simultaneous changes of Brix values are considered, the mechanical treatment is the more efficient tool for increased colour extraction. Inclusion of processing costs allows to determine the cost-benefit-ratio of the discussed treatments and claims mechanical treatment to be of higher interest from an industrial perspective.

The project enables companies to re-define their approach with regards to processing techniques for production of high-colour CJC. Recommendations of enzymatic maceration can be rejected, instead focus is shifted towards cell disintegration by mechanical means.

Popular Abstract

How to increase the orange colour in carrot juice
– Enzymatic versus mechanical forces –

Carrot juice has become a very popular vegetable juice during the last years and its consumption is increasing continuously. The juice is claimed to have many health-beneficial effects which are attributable to its high content of carotenoids. For the beverage industry, the quality of carrot juice is mainly defined by its colour content. Against this background, you might ask yourself, where the intense orange colour of the carrot juice comes from and how you obtain the juice from the raw vegetable. The report deals with the production process of carrot juice, which challenges manufacturers face in terms of colour extraction and how they circumvent those issues.

In carrots orange colour pigments – the so-called carotenoids – are located inside the plant cells. They are encapsulated by the cell wall which is built of a complex network of indigestible polysaccharides (pectin, cellulose and hemicelluloses). To obtain orange carrot juice, these colour pigments need to be released from the cells and migrate into the liquid phase. But as if the cell wall as strong physical barrier is not enough, this transfer is also limited by the fact that the carotenoids are not water- but fat-soluble. These two aspects imply, why and how manufacturers have to think of efficient ways to crack the carrot cells open and extract as much carotenoids as possible into the juice. In research, many different techniques have been tried out and discussed. Among various others, treatments of carrots with heat, enzymes and/or with mechanical forces have shown to be successful. The report presents details to each method and highlights the ability of enzymatic in comparison to mechanical treatment on carrot cells to increase the colour content in carrot juice.

But if it has been found out already that these techniques are suitable for the given aim – what is the purpose behind this project then? In the beverage industry carrot juice is often further processed to carrot juice concentrate (CJC) by evaporation of water. The CJC is then sold to end producers, who use it for juices, ACE-drinks, yoghurt etc.. In this concentration step, the ratio of carotenoids to soluble solids in the juice play an important role: It reflects the concentration factor for colour and thus determines the colour intensity in the final CJC. Soluble solids are sugars like saccharose, and other monosaccharides (fructose and glucose) and are measured as °Brix. These compounds originate from the degraded carrot cell wall, but also from the interior of the carrot cells. Most of the existing studies did not consider this concentration factor, but on the market the colour at a given Brix is the main selling parameter for carrot juice and its concentrate. Therefore, this report focused on the evaluation of the known techniques from an industrial perspective.

There are various methods to produce carrot juice – the most important steps are as described below. First, the raw carrot is grinded into small pieces, then it is mixed with water in a 1:1 ratio. This mash is heat-treated to kill off potential bacteria, to inactivate enzymes which are related to quality losses and also to soften the cell material of the carrot. After a subsequent fine-grinding step, the first separation takes place, where carrot juice is separated from the solid particles. What is left is the so-called pomace which still contains up to 50 % of carotenoids encapsulated in the cells. Different ways of pomace extraction are performed now to get out even the last colour pigments from the cell material and drag them into the juice. To do so, the pomace is diluted with water again and different treatments are applied to crack open the residual intact carrot cells.

In this report, enzymatic and mechanical treatment of the pomace have shown to result in very different concentration factors for colour. Generally, the idea of enzymes is that they work on the cell wall, degrade its constituents into smaller building blocks and thus open up the cells. The trial revealed that enzymes are too weak to really crack the cells open. Hence, carotenoids remain inside the cells and only the Brix values go up because of the monosaccharides which are released. In comparison to that, mechanical treatment, where the carrot mash is forced through a very small hole with high pressure, seem to be much better. The cells get totally disrupted and the carotenoids can stream out of the cells easily. At the same time no monosaccharides are formed as the cell walls do not get degraded into their building blocks. This was visualized by microscopic pictures and measurements of particle sizes of the carrot mashes.

In conclusion, mechanical treatment is much more useful to obtain high colour contents in carrot juice and CJC as this technique presents a higher concentration factor for colour from the juice to concentrate. Hence, statements from literature can be re-evaluated and it is recommended to focus on mechanical over enzymatic techniques to improve the colour extraction from carrots. This approach is supported and verified by calculations on processing costs and determination of cost-benefit-ratios of the two treatment. To cut a long story short, the report combines two perspectives which has not been done before in such manner. The effects of certain processing techniques are not only evaluated as scientific results, but also from an industrial point of view and thus point out the applicability of certain processing techniques for companies that produce carrot juice and CJC.

• author: Riehle, Sophie-Antonia Margarethe
• supervisor: Ingegerd Sjöholm
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM01 20151
• year: 2015
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: mechanical treatment, enzyme maceration, cell wall, carrot pomace, carrot juice concentrate, beta-carotene, colour extraction, carrot, orange colour, processing technique, industrial perspective, livsmedelsteknik, food engineering
• publication/series: Food Technology and Engineering
• language: English
• id: 8167911
• date added to LUP: 2015-11-13 13:48:16
• date last changed: 2015-11-13 13:48:16