Breaking new ground in the analysis of juice with steam distillation

The International Fruit and Vegetable Association held a series of Technical Webinars including a Quality webinar with Dr Eduard Wiedenbeck as a guest speaker

Here we review the analysis of citrus fruit juices, particularly determining the quality of citrus essential oils according to their main constituent, D-Limonene.

As 2021 was the FAO’s International Year of Fruits and Vegetables, it is inevitable to remind ourselves of the important role that citrus fruits play in maintaining our health. Oranges, lemons and grapefruits are rich in phytonutrients, a type of antioxidant that neutralizes free radicals in our body and prevents many health issues.¹ Nevertheless, both as consumers and as producers, we should take a closer look at the quality-related compounds that are present in citrus fruits, especially at D-Limonene, which is the main constituent of citrus essential oils. D-Limonene is mainly present in the peel of citrus fruits, such as oranges and lemons, and is used by the plants as a natural insecticide protecting their nutrient-rich fruits from parasites. For us, the smell of D-Limonene is characteristic of a fresh orange scent which is not surprising considering that more than 90 % of the oil content of oranges is comprised of this compound. In our daily life, D-Limonene is used as a dietary supplement and as a fragrance ingredient for cosmetic products. Because of its refreshing scent, it is often used to mask the bitter taste of alkaloids and for all kinds of cosmetic products. And since D-Limonene is the main constituent of citrus essential oils which are found in the fruit peel, the compound is also present in fruit juice where it contributes to the flavour of the fruit. Due to heavily industrialized juice production with cold press extraction of oranges, it is unavoidable that this compound enters fruit juice in significant amounts.

D-Limonene – beneficial or not?

Although it appears to be safe and even positively accepted for most human-related uses, there may also be negative implications if D-Limonene is administered in higher concentrations. If this compound is applied to skin, it may cause irritation from contact dermatitis. This topical effect becomes even more significant when this compound is ingested at high concentrations with irritations in the throat as the consequence. Further studies show that the liver was identified as a critical target organ following oral administration of D-Limonene.² But should we now stop consuming citrus fruits and their juice products?

The answer is a comforting ‘no’. Thanks to responsible national authorities such as the European Fruit Juice Association (AIJN) and the United States Department of Agriculture (USDA) which have set maximum levels that should not be exceeded, it is ensured that the consumer gets a taste of the highest quality of juice products. Thanks to these standards, D-Limonene is maintained at low enough concentrations to be harmless. How can one measure D-Limonene levels? An established method with steam distillation according to Scott and Veldhuis has proven its reliability since 1966.³ However, determining D-Limonene via manual steam distillation and subsequent titration analysis is usually tedious, slow and labour-intensive. Some quality control laboratories report that they need 20 minutes just to distil one single sample. Recently, efforts have been made to speed up the process by using a distillation unit with an integrated steam generator. As a result, the steam distillation time has decreased drastically from 20 minutes to 1 minute per sample! More details on these time savings can be found in BUCHI’s latest Application Note. In this case the juice industry should be on a viable way to facilitate a high throughput analysis that is still in line with the established method.

¹ Okwu, D.U.; Citrus fruits: A rich source of phytochemicals and their roles in human health, International Journal of Chemical Sciences 2008, 6(2), 451-471

² Lee B.M. et al.; Safety Evaluation And Risk Assessment Of d-Limonene, Journal of Toxicology and Environmental Health 2013, 16 (1), 17-38.

³ Scott, W.C.; Veldhuis, M.K.; Rapid Estimation of Recoverable Oil in Citrus Juices by Bromate Titration, Journal of Association of Official Analytical Chemists 1966, 49 (3), 628–633.

 Dr Eduard Wiedenbeck is Product Manager for Kjeldahl Solutions at Büchi Labortechnik in Switzerland. He has presented this topic at the IFU Technical Webinars 2021. The webinar can be seen on-demand by clicking here.”

https://ifu-fruitjuice.com/store/viewproduct.aspx?id=18465372

We have the technology – the key to sweetness exists

Tetra Pak provide some insight into their ground-breaking tech designed to keep our favourite beverages sweet and delicious, but less of the sugar

There has been an abundance of attention around reduced sugar drinks, not least because of the much-discussed sugar tax. But juice trails its counterparts in this space.

Tetra Pak, together with Sumol+Compal, has developed technology that can reduce the sugar content in juice to the exact requirements of the brand using a fermentation process. The fermented de-sugared juice is a true ‘clean label’ product with no additional ingredients.

This innovative solution can reduce sugar in juice while maintaining its taste profile, colour, mouthfeel, and nutritional content. Using fermentation, it is possible to remove the sugar while keeping all the benefits of the juice, plus fermentation is trendy in the added value category. Indeed, almost a third of the USD1.5 billion invested in alternative proteins last year went towards companies using fermentation.

According to recent research from Mintel, there is a thirst from consumers globally for this type of product. In Spain, 75% of juice consumers cited sugar as a reason for limiting the amount of juices & smoothies they drink. Meanwhile in China, 43% of juice consumers consider sugar content an important factor in choosing juice drinks. In the UK, 42% of juice buyers say that health benefits would encourage them to spend more on juice drinks.

1. Can you explain, in layman’s terms, the kind of technology being used to reduce the sugar content in these juices?

We are using fermentation, a natural biological process to remove sugar while retaining all the benefits of the juice. The secret lies in combining a unique yeast strain with the optimal process and design parameters so that all sugar is removed, and re-blended with standard juice to achieve the desired final product.

1. How is this technology applied to achieve the desired effect?

Step 1. Fermentation:

• Complete sugar removal down to 0% is achieved with optimal process and design parameters in combination with a unique yeast strain which gives consistent product quality – no off flavors, nor increasing the natural acidity present in a fruit juice, thus keeping fruit juice flavour and fundamental nutritional value.
  • By products: the yeast that is added in fermentation tanks is removed in the clarifier
  • By products: the alcohol which is created during fermentation is removed in the de-alcoholisation unit

Step 2. Clarifier:

• Removes the yeast cells to stop fermentation process
• Secure product quality (no rupturing of yeast cells, to avoid sensory impact, very low pulp / turbidity reduction)
• The yeast size, shape and floculation behaviour, make it possible to remove the yeast while only a minor amount of juice pulp is removed, keeping the juice nutritional and maintaining its sensorial profile
• The process design does not break the yeast cell walls, meaning that there is no release of off flavour (yeasty) compounds into the juice

Step 3. De-alcoholisation unit

• Removing alcohol in a gentle way while keeping juice taste and aromas
• The quantity is completely controlled
• The product after the de-alcoholisation unit: a valuable ingredient of 0% desugared juice

Step 4. Product formulation:

• The final sugar level in the product is controlled by blending the 0% desugared juice with 100% juice in a normal juice line after the fermentation process
• With this production line solution, we are able to keep the number of ingredients to a minimum, while maintaining good taste, colour, mouthfeel as well as nutritional content

1. Were there any R&D challenges? How were these overcome?

Some of the challenges faced when trying to find a refined process to produce de-sugarised juice included:

• Watering down and adding low-calorie sweeteners meant that there would be a lower juice content and no increased nutritional density
• Removing sugars using filtration technologies didn’t achieve the desired sensory result – it resulted in changes to the juice matrix and impacted nutritional value
• Enzymatic conversion of sugars to a by-product had some impact on sensory result and may not be perceived as a natural process
• Multiple yeast strains had to be tested to find the optimal solution

1. Can you tell me more about the fermentation process? What method does your company use to achieve your desired result?

We decided to use fermentation as it is a natural biological process that can remove sugar while maintaining the taste profile, colour, mouthfeel and nutritional content.

First, the yeast is added to the juice. Once this has been done, the yeast is then removed by a clarifier, before the alcohol is then removed in a de-alcoholisation unit. This produces the de-sugarised juice and there is then the possibility to re-blend this 0% sugar juice with 100% juice to achieve the desired product, such as 50% sugar juice.

The specific yeast strain used was selected after screening dozens of strains, and is used in various traditionally fermented foods such as wine or cider.

1. Can you tell me anything about the patents on this technology? Once the word gets out, how do you foresee other companies making use of this kind of technology? Or is that not possible?

This technology solution is similar to our revolutionised JNSD line that Tetra Pak launched last year, which was a new combination of existing technology (UV + filter). As such, the de-sugarised juice method is a combination of existing technologies, albeit in a new and unique way.

Due to the fact that these technologies are already in use, it is not possible to patent. However, in order to achieve the desired quality and benefit from the expert knowledge developed during trials, customers need to combine equipment from Tetra Pak with the unique yeast strain from Sumol + Compal.