Changes of microbial population and some components in carrot juice during fermentation with selected Biﬁdobacterium strains Szila ´ rd Kun, Judit M. Rezessy-Szabo ´ , Quang D. Nguyen *,A ´ goston Hoschke Corvinus University of Budapest, Faculty of Food Science, Department of Brewing and Distilling, H-1118 Budapest, Me ´nesi u ´t 45, Hungary 1. Introduction Recent social and economic developments may lead to serious health problems. Stress and the busy lifestyle of humans induce the so-called diseases of civilization such as heart attack, high- blood pressure, intestinal disorders, and various types of cancer. Improper nutrition may cause colon problems and negatively inﬂuence the immune system, but a balanced nutrient intake ensures a long and healthy life. One promising solution for the prevention or elimination of these diseases is the design and consumption of probiotic foods which contain living micro- organisms [1]. Clinical evidence is available to prove that probiotic foods beneﬁt humans by maintaining or improving their intestinal microbial balance [2]. These micro-organisms have numerous health promoting effects such as alleviation of lactose intolerance [3], prevention of intestinal tract infections and colon cancer [4], strengthening of the immune system [5], reduction of serum cholesterol level [6], stimulation of calcium absorption, synthesis of vitamins (vitamin B, nicotinic acid, and folic acid) [7], and enhancement of protein digestibility. They also act as antagonists of food-borne pathogens [8]. Most probiotic foods consumed by humans contain mainly lactobacilli and/or biﬁdobacteria, but some probiotic products even have Enterococcus strains or yeast such as Saccharomyces boulardii [9]. Among them, biﬁdobacteria have an outstanding importance in the microbial ecology of the human gut [10]. Historically, Biﬁdobacterium was isolated and described in 1899 by Henry Tissier at the Pasteur Institute, Paris, France. It is a Gram-positive bacterium with high G + C content (>55 mol%) in DNA [11] and inhabits the intestinal tracts of humans and animals. Morphologically, biﬁdobacteria are non- motile, asporogenous, pleomorphic rods of variable appearance, somewhat curved and clubbed, and often branched. Biﬁdobacter- ium species are able to utilise a wide range of mono- and disaccharides as well as oligosaccharides due to their enzyme system. Unlike lactic acid bacteria or other micro-organisms, glucose (hexose) metabolism in biﬁdobacteria is unique; it is often referred to as the ‘biﬁdus pathway’. The key enzyme in this pathway is a fructose-6-phosphate phosphoketolase (F6PPK), which cleaves fructose phosphate to erythrose-4-phosphate and acetyl phosphate [12]. Theoretically, through the biﬁdus pathway, 1 mol lactic and 1.5 mol acetic acid are generated from the fermentation of 1 mol of glucose [13]. However, in practice, there may be some deviation from this ratio due to phosphoroclastic cleavage of pyruvate. Process Biochemistry 43 (2008) 816–821 ARTICLE INFO Article history: Received 5 August 2007 Received in revised form 25 March 2008 Accepted 27 March 2008 Keywords: Biﬁdobacterium Probiotic Carrot juice Organic acid Fermentation Carotenoids ABSTRACT Probiotics have several advantages for human health. Since most of the probiotic foods are dairy products, they cannot be consumed by humans who are allergic to milk proteins or have severe lactose intolerance. While looking for alternative food matrices, the suitability of carrot juice as a raw material for the production of probiotic food with Biﬁdobacterium strains (B. lactis Bb-12, B. biﬁdum B7.1 and B3.2) was investigated. Pasteurization of freshly prepared carrot juice at 80 8C for 20 min decreased the microbial population to below the detection limit (10 colony-forming unit (cfu)/ml). All tested biﬁdobacteria strains were capable of growing well on pure carrot juice without nutrient supplementation. Moreover, 10 7 cfu/ml initial cell concentrations resulted in 10 8 cfu/ml after 6 h of incubation, and were kept viable up to the end of fermentation (24 h). Volumetric productivities of B. lactis Bb-12, B. biﬁdum B7.1, and B. biﬁdum B3.2 were 2.16  10 10 cfu/l h, 4.65  10 10 cfu/l h, and 3.85  10 10 cfu/l h, respectively. Due to intense metabolism of the bacteria strains, carrot juice media were acidiﬁed to a pH level of less than 4.5. During the fermentation, the amounts of glucose and sucrose decreased signiﬁcantly. Meanwhile the fructose concentration did not change. Degradation of carotenoids (a-carotene and b-carotene) was between 15–45% depending on the strain used. Production of lactic and acetic acids was in the range of 14.8–16.7 mg/ml and 3.3–5.3 mg/ml, respectively. ß 2008 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +36 1 482 6041; fax: +36 1 482 6558. E-mail address: quang.nguyenduc@uni-corvinus.hu (Q.D. Nguyen). Contents lists available at ScienceDirect Process Biochemistry journal homepage: www.elsevier.com/locate/procbio 1359-5113/$ – see front matter ß 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2008.03.008