Optimization of ingredients for Lactobacillus fermented beverages

Abstract

The ingredients generally used in the fermentation of probiotics tend to give an off-flavour to the fermentation product which is not ideal when producing e.g. fruit drinks. The aim of this master thesis was to evaluate if the concentration of such ingredients could be lowered and also to investigate whether there are other ingredients that could act as substitutes to those ingredients giving off-flavours. The growth, stability and taste of the fermentation products containing the ingredients and probiotics, as well as the fermentation product put in a fruit model system, was evaluated. The experimental work included changing the concentration of the ingredient giving the off-flavour and exchanging it with substituting ingredients during the fermentation of three different probiotic bacteria. The bacterial content was measured using a plate count method and the stability of the fermentation product was evaluated after one week of storage in 4C. After putting the fermentation product in a fruit juice, the stability was measured during four weeks of storage and a simplified sensory evaluation was done.

It was found that the ingredients that gave the significantly highest growth was generally the ingredient normally used during the fermentation and none of the substituting ingredients were as successful in supporting growth. It was also concluded that the type of bacteria will have an effect on the final bacterial content in the fermentation product and the sensory properties where some strains had a better taste profile than others.

Popular Abstract

Probiotic fruit drinks – Is it possible to combine high bacterial growth with great taste?

Wouldn’t it be great to have a probiotic fruit drink that just taste like fruit, with no off-flavours?
When fermenting probiotics, ingredients that provide off-flavours are often used, resulting in for
example a meat and umami tasting strawberry juice on your breakfast table. That does not sound
too good, does it?

Probiotics are bacteria that provide a health benefit to the individual ingesting them. It is therefore
not surprising that the field of probiotics have grown as much as it has during the recent years. There
are many benefits connected to probiotics in fruit drinks but there are also challenges. For example,
fruit drinks provide a natural source of sugar which bacteria need for survival. However, fruit drinks
are very different from the natural environment in which probiotics can be found. This makes it
necessary to add additional ingredients to provide sufficient nutrients and facilitate survival of the
bacteria in the harsh environment of a fruit drink.

To minimize or remove the umami taste and to avoid that the fruit drink tastes more like meat broth,
the concentration of these ingredients can be reduced. This was done during the experiments.
Although, reducing the concentration will also decrease the number of bacteria in the fermentation
product due to less nutrients available for the bacteria to utilize. However, the fermentation
products containing a lower concentration will have a better taste with less off-flavours. It is
therefore a matter of priority; higher concentration of these ingredients will result in better growth
and more off-flavours while lower concentration will result in less growth and better taste of the fruit
drink.

Substituting these ingredients with other ingredients might therefore be a possibility. A sensory
evaluation of the fermentation products containing these substituting ingredients revealed that they
did not have the umami taste but rather a taste of vegetables which might be easier to disguise in a
juice. This was confirmed since the samples put in juice tasted very good during the entire storage
period of four weeks. However, the bacterial content in all samples containing these substituting
ingredients were not as high as expected.

The different bacteria used in the experiments also effected the taste of the juices. Some bacteria
had a better taste than others and some might not be suitable to be put in juice due to the bad taste
of the bacteria itself. In addition, one of the bacterial strains did not grow as well as the others,
suggesting that this type of bacteria might require an essential nutrient which was not present in the
growth medium used in this experiment.

After investigating these possibilities, it is clear which ingredients that facilitate the highest bacterial
growth and which did not work at all. One suggestion for future experiments might be to combine
the substituting ingredients with the ingredients normally used during the fermentation to increase
the bacterial content. The concentration of the ingredients creating off-flavours in combination with
the substituting ingredients should be as small as possible, still increasing the bacterial growth, but
not as high as to get the off-flavour.

These findings will facilitate the quest to develop a fruit drink which not only provide a large amount
of probiotic bacteria but also a great taste. In conclusion, the probiotics tested seems to require the
normally used ingredient to achieve the highest growth possible, but hopefully, this might change
with further development, resulting in fruit drinks simply tasting like fruit.

• author: Olsson, Rebecka
• supervisor: Elisabeth Uhlig
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLG820 20171
• year: 2017
• type: H2 - Master's Degree (Two Years)
• subject: Agriculture and Food Sciences
• language: English
• id: 8912093
• date added to LUP: 2017-06-13 17:27:40
• date last changed: 2017-06-13 17:27:40