Fruit Fermentation by Lactic Acid Bacteria

Vegetable and Fruit Fermentation by Lactic Acid Bacteria 

Raffaella Di Cagno, Pasquale Filannino, and Marco Gobbetti 

Department of Soil, Plant and Food Sciences, University of Bari Aldo Moro, Italy 

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The sugars in fruits such as grapes are feimented by yeasts to produce wines. In winemaking, lactic acid bacteria convert malic acid into lactic acid in malolactic fermentation in fruits with high acidity. Acetobacter and Gluconobacter oxidise ethanol in wine to acetic acid (vinegar). 

Eresh fruits are strongly recommended in the human diet since they are rich in vitamins, dietary fibres, minerals and antioxidants. In particular, sweet cherries contain remarkable contents of polyphenols, such as anthocyanins, which give them the characteristic colour and antioxidant properties. Fermentation can further enhance the antioxidant properties of sweet cherries. Sweet cherry Prunusavium L.) puree fermented by selected autochthonous lactic acid bacteria (L. plantarum, Pediococ-cus acidilactici, Pediococcus pentosaceus and Leuconostoc mesenteroides subsp. mesenteroides) at 25 C for 36h has been reported to exhibit significantly higher DPPH radical-scavenging capacity compared to unfermented sweet cherry puree (Cagno etal., 2011). 

Coconut water is the liquid endosperm fluid of the coconut fruit which contains high amounts of essential nutrients and minerals. This endosperm fluid is a widely consumed as a beverage in many parts of the world as it provides hydration along with increased nutritional, health and medicinal benefits. In addition to being used as a medium constituent, it also acts as a natural biocatalyst One of the fermented products of coconut water, coconut water kefir, is made by fermenting coconut water with the kefir granules which contain essential lactic acid bacteria and yeast spp. known to have health benefits for a disease-free life. It has many applications in the food industry and functional food market It is used as one of the important constituents in a variety of products or can be consumed as-it-is . It is known to have no undesirable side effects and is said to improve digestioa This paper reviews the functional properties of coconut water, its applications in the food industry and recent advancements in this area. 

Since around 1800, the mechanism of fermentation has been studied in a scientific way. It started when German scientist Erxleben discovered that yeast induces fermentation. Louis Pasteur, a French scientist, made many contributions to microbiology. He explained that bacteria produce lactic acid, which then conserves the food. Pasteur also noticed that unwanted fermentation can be stopped by heat treatment of the substrate (pasteurization). This technique is still widely applied today to treat milk or fruit juices. Actually, the production of neat lactic acid was also the first nonfood industrial application of fermentation. 

Part of the original fruit acids may be consumed by yeasts and, especially, bacteria (see malolactic fermentation ). On the other hand, yeasts and bacteria produce acids, e.g. succinic and lactic acids. Furthermore, acid salts become less soluble as a result of the increase in alcohol content. This is the case, in particular, of the monopotassium form of tartaric acid, which causes a decrease in total acidity on crystallization, as potassium bitartrate still has a carboxylic acid function. 

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