The present invention relates to fruit based fermented products containing propionate and uses thereof.

Yeasts and acetic acid bacteria are the most common microorganisms involved in the spontaneous fermentation of fruits, converting carbohydrates to alcohol and/or acetic acid. Also, these organisms can act as spoilage organisms of fruit based products such as juices. On the other hand, Propionibacteria are involved in the fermentation of dairy products, most commonly cheeses, converting carbohydrates and lactic acid to mainly propionic acid, but also some acetic acid, carbon dioxide and succinic acid. Propionic acid especially inhibits yeasts and moulds but also other bacteria.

Babuchowski et al. (Lait (1999), 79, 113-124) discloses the use of Propionibacteria to produce fermented vegetables. The propionic acid content of red beet juice fermented withPropionibacterium freudenreichiiandPropionibacterium thoenii, respectively, reached a value of 1.56% and 2.18%, respectively, after 14 days of fermentation. Such a fermentation period is much to long for industrial application (high costs and high risk for contamination). When fermentation was done with propionibacteria and lactic acid bacteria together, the propionic acid content of the fermented red beet juice reached a maximum value of only 0.12% after 1 day of fermentation, whereas prolonged fermentation of 10-14 days resulted in a lower propionic acid content (about 0.04%).

It was now surprisingly found that when liquid fruit preparations, like juices, extracts, purées, were purposively fermented with members of the genusPropionibacterium, a ferment can be obtained having a high propionate content, even without the addition of additional nutrients, when fermentation was done for a period of 1 to 4 days. The ferment inhibits yeasts and moulds when applied in e.g. fruit based products, but, advantageously, hardly influences the taste and flavour of the fruit based product, even when applied in a high concentration.

Thus, in a first aspect the present invention discloses a method to prepare a fruit ferment containing propionate by subjecting a liquid fruit preparation to fermentation by a propionic acid-producing bacterial strain. The method in particular comprises:

i) obtaining a liquid fruit preparation,

ii) optionally supplementing the liquid fruit preparation with water and/or with additional components to support fermentation,

iii) fermenting the optionally supplemented fruit preparation with a propionic acid-producing bacterial strain,

iv) optionally further processing the fermentation product, to obtain the fruit ferment.

A fruit for use in the methods and fruit ferments as described herein is the edible, fleshy, seed-associated structure of certain plants. Such a fleshy structure typically has a natural water content of at least 65% (w/w), even at least 70% (w/w) or at least 75% (w/w). Such fruits include sweet fruits like apples, pears, oranges, grapefruits, grapes, strawberries, melons, bananas, pineapples, passion fruits, peaches, mangos, guavas, non-sweet fruits like lemons, avocados, and vegetable-like fruits like tomatoes, cucumbers, bell peppers, pumpkins. A preferred fruit for use in the method of this aspect is a sweet fruit and/or a tomato. An especially preferred fruit is apple, pear, orange, grape, pineapple, melon or tomato, or any mixture thereof. The fruits for use in the methods and fruit ferments as described herein do not include nuts and cereal grains.

The fruit of choice is processed to obtain a liquid fruit preparation. Suitable liquid fruit preparations for instance are a juice, an extract or a purée (mashed fruit). Processing of the fruit is done using techniques commonly known to those skilled in the art. The liquid fruit preparation may be obtained from a concentrate. A single fruit type or mixture of two or more fruit types may be used.

The liquid fruit preparation optionally may be supplemented with water and/or with additional components necessary to support and/or improve bacterial fermentation. This supplementation may be done prior to and/or during fermentation.

Dilution of the liquid fruit preparation with water suitably may be done to obtain a suitable sugar level for the bacterial strain used in the fermentation and to advantageously accelerate the fermentation process. A suitable sugar level of the liquid fruit preparation may be 1.5 to 10% (w/w).

The liquid fruit preparation, optionally diluted, may further be supplemented with additional components necessary to support and/or improve bacterial fermentation. For instance, the additional components may be additional carbon source such as glucose or sucrose, additional nitrogen source such as yeast extract and/or additional minerals and/or vitamins. Advantageously, the amount of additional components in general is low, so that sensory properties of the resulting ferment are not negatively affected. It is preferred not to supplement the liquid fruit preparation at all.

Fermentation is done using a propionic acid-producing bacterial strain. Preferred propionic acid-producing bacterial strains are strains of the genusPropionibacterium. Suitable species includePropionibacterium freudenreichii, Propionibacterium shermanii, Propionibacterium acidi-propionici, Propionibacterium thoeniiand/orPropionibacterium jensenii. Examples of other propionic acid-producing bacterial species areClostridium propionicum, Selenomonas ruminantumand/orBacteroides ruminicolaand/or species of the genusVeillonella. PreferredPropionibacteriumspecies arePropionibacterium freudenreichii, Propionibacterium shermaniiand/orPropionibacterium acidi-propionici. A single strain or a mixture of two or more strains or species may be used.

In one embodiment, the fermentation with a propionic acid-producing bacterial strain is supplemented with one or more strains of lactic acid-producing bacteria. Suitable lactic acid producing-bacterial strains are found within lactic acid bacteria belonging to the order Lactobacillales or within moderately thermophilicBacillusspecies. Examples of lactic acid bacteria areLactobacillus casei, Lactobacillus acidophilus, Lactobacillus delbrueckii, Lactobacillus paracasei, Lactobacillus helveticus, Lactococcus lactisand/orLactococcus plantarum. Examples of moderately thermophilicBacillusspecies areBacillus coagulans, Bacillus smithiiand/orBacillus thermoamylovorans. Moderately thermophilicBacillusspecies are defined asBacillusspecies that are capable of growing at temperatures between 30-65° C.

Lactic acid-producing bacteria are advantageously used to convert sugars in the liquid fruit preparation to lactic acid, which lactic acid is particularly suitable as a carbon source for the propionic acid-producing bacterial strain. Supplementing the fermentation with one or more strains of lactic acid producing bacteria may be done in various ways. It may be done by firstly fermenting the liquid food preparation with one or more strains of lactic acid producing bacteria and then fermenting the resulting lactic acid containing fermentation broth or fermentation fluid (i.e. with or without lactic acid producing bacteria) with a propionic acid-producing bacterial strain. It also may be done by simultaneously fermenting the liquid food preparation with one or more strains of lactic acid-producing bacteria and of propionic acid-producing bacteria. In the latter option, the lactic acid-producing bacteria may constitute, at the end of the fermentation process, from 10% to 90% of the total weight of bacteria used in the fermentation process.

The fermentation process further preferably is substantially devoid of contaminating microorganisms, i.e. other microorganisms than the ones described hereinabove. For instance, at the end of fermentation the percentage of contaminating microorganisms is at the most 5% (w/w) of the total amount of biomass produced.

The fermentation conditions are typically chosen conform the growth requirements of the microbial strain(s) to be used in the fermentation process.

It is important to maintain the pH of the liquid fruit preparation, initially and during fermentation, at a value between 4.5 and 7, preferably between 5 and 7. This may be done by the addition of a suitable base, e.g. sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, ammonium hydroxide, ammonium carbonate, and/or natural sources containing these alkali substances like lime, limestone, chalk.

The fermentation process is typically done for a time period suitable to consume the majority of the available sugars, preferably all of the sugars, and preferably also the majority or all of the lactate, if present. However, it is also possible to ferment only part of the available sugars. The available sugars typically are the sugars naturally present in the fruit and any sugar added as additional carbon source. At the end of fermentation, the propionate level of the fermentation fluid (i.e. measured after separation of the microbial biomass) may vary from 0.25 to 10% (w/w).

Typically, fermentation is carried out for a time period from 20 to 120 hours, preferably from 20 to 100 hours, more preferably from 30 to 90 hours.

The fermentation process is generally carried out at a temperature in the range of 10 to 70° C., in particular in the range of 25 to 55° C., more in particular in the range of 25 to 35° C.

After fermentation is ended, the fermentation product may optionally be further processed as desired, e.g. depending on its intended use. Advantageously, it is in general not necessary to apply further processing steps to improve sensory properties.

For instance, solids including biomass may be separated from the fermentation product to obtain a fermentation fluid. Any method known to the skilled person for this solid removal may be used, e.g. ultrafiltration, microfiltration, static decantation, or centrifugation. It is also possible to remove only part of the solids from the fermentation product.

The fermentation product including solids or the fermentation fluid from which solids are separated may also be concentrated. Concentration may be carried out by any method known in the art. It may be carried out to form a concentrated solution, for instance by concentrating up to about 20 times, such as 8 to 16 times. Suitable methods include for example (vacuum) evaporation and methods based on membrane technology, such as reverse osmosis. It is also possible to prepare a solid granular product, via for example extrusion or spray-drying.

The fermentation product including solids, the fermentation fluid from which solids are separated or the concentrated product may also be pasteurized or sterilized.

Standardization may be necessary to achieve a fruit ferment having a consistent composition.

In a second aspect, the present invention relates to a fruit ferment containing propionate.

The fruit ferment of this aspect is obtainable by subjecting a liquid fruit preparation as described in the first aspect to fermentation using a propionic acid-producing bacterial strain, optionally together with a lactic acid-producing bacterial strain, as also described in the first aspect.

The fruit ferment comprises propionate in a concentration ranging from 0.25 to 80% (w/w), preferably from 0.5 to 70% (w/w), more preferably from 1 to 60% (w/w). The propionate content thereby depends on the water content of the fruit ferment and on the presence or absence of bacterial biomass. Typically, the fruit ferment may have a water content of 0 to 99.5% (w/w), depending on the further processing (concentrating and/or drying) of the fermentation product after fermentation.

Preferably, the fruit ferment further comprises acetate in a concentration ranging from 0.1 to 60% (w/w). The weight ratio of propionate to acetate in such a ferment thereby ranges from 0.5 to 10, preferably from 1.5 to 5.

Also preferably, the fruit ferment further comprises succinate in a concentration ranging from 0.002 to 1% (w/w). The weight ratio of propionate to succinate in such a ferment thereby ranges from 200 to 15, preferably from 150 to 25.

The terms propionate, acetate and succinate as used herein are meant to encompass the acid as well as the salt form. In that regard, typical salts are sodium, potassium, ammonium, calcium and magnesium salts, or combinations thereof.

The fruit ferment further may comprise part or all of the propionic acid-producing bacterial cells and, when used, the lactic acid producing bacterial cells, of the fermentation process.

As a consequence of fermentation, the fruit ferment further has a reduced sugar content as compared to the starting liquid fruit preparation. At least 5% of the amount of sugar present in the starting liquid fruit preparation, preferably at least 10%, more preferably at least 20%, is converted by fermentation. Sugar in this context refers to hexose mono- and/or disaccharides, including fructose, glucose and/or sucrose.

In one embodiment, the fruit ferment of this aspect is obtainable by the methods as described in the first aspect.

The fruit ferment of this aspect may be a food or beverage as such and/or may be used as an additive for or an ingredient of a food and/or beverage.

A further aspect of the invention relates to a composition comprising the fruit ferment of the previous aspect.

Such a composition may be an additive composition for food and/or beverages comprising additional ingredients next to the fruit ferment. Examples of such additional ingredients are lactic acid and/or salts thereof, acetic acid and/or salts thereof, vinegar, cinnamic acid and/or salts thereof, vanillin, nisin, sorbic acid and/or salts thereof and fermentation products containing lactic acid and/or salts thereof, acetic acid and/or salts thereof, propionic acid and/or salts thereof, benzoic acid and/or salts thereof, and/or one or more of the following components: nisin, natamycin, polylysin, bacteriocins.

The fruit ferment or the additive composition comprising the fruit ferment as described herein may advantageously be used in food and/or beverages, for instance to inhibit yeast and/or mould growth in the food or beverage. Because of the neutral or delicate taste and flavour of the fruit ferment, it does not provide any substantial off-taste and/or off-flavour to the food or beverage, even when applied in a high concentration. Typically, the fruit ferment may be added to a food or beverage to provide a propionate level in the food or beverage in a range of 0.005 to 1% (w/w), preferably in a range of 0.02 to 0.5% (w/w), more preferably in a range of 0.05 to 0.2% (w/w).

In one embodiment, the fruit ferment is advantageously added to a fruit-based food and/or beverage, in particular to a fruit-based food and/or beverage that contains the same type of fruit as the fruit that is used for preparing the fruit ferment. In this way, the fruit-based food or beverage obtains novel properties, for instance with regard to taste, flavour, colour, storage stability. Properties like taste, flavour and colour of the fruit ferment are thereby advantageously in line with those of the fruit-based food and/or beverage. A fruit-based food and/or beverage typically may have a fruit content varying from about 3% (w/w), such as in soft drinks, to 100% (w/w), such as in undiluted fruit juices, fruit purées or fruit concentrates.

Thus, in a further aspect there is provided a method to improve the sensory properties and the storage stability of a fruit-based food and/or beverage by supplementing the food and/or beverage with a fruit ferment as described herein. The fruit ferment thereby preferably has a taste, flavour and/or colour profile that does not substantially deviate from the profile of the fruit-based food and/or beverage. For instance, a melon ferment may be added to an apple-based food and/or beverage, whereas a tomato ferment may not. More preferably, the fruit ferment is prepared from the same fruit or fruits as the fruit or fruits included in the fruit-based food and/or beverage.

The fruit ferment when still containing microbial cells further may advantageously be used a probiotic.

