Kefir

Review: Functional Properties
of Kefir
ZEYNEP B. GUZEL-SEYD˙IM1, TUGBA KOK-TAS1, ANNEL K. GREENE2
and AT˙IF C. SEYD˙IM1
1Department of Food Engineering, S¨uleyman Demirel University, C¸ ¨un¨ur, Isparta, 32260, Turkey
2Department of Animal & Veterinary Sciences, Clemson University, Clemson, SC, 29634-0328, USA
Kefir is a unique cultured dairy product due to combined lactic acid and alcoholicfermentation of lactose in milk. Kefir is
produced by microbial activity of “kefir grains” which have a relatively stable and specific balance of lactic acid bacteria
and yeast. Due to the claimed health benefits of kefir which include reduction of lactose intolerance symptoms, stimulation of
the immune system, lowering cholesterol, and antimutagenic and anticarcinogenic properties, kefir hasbecome an important
functional dairy food and consequently, research on kefir has increased in the past decade. In the following review, recent
studies on the functional properties of kefir are reviewed.
Keywords fermented milk, health, probiotic, anticarcinogenic
INTRODUCTION: HEALTH BENEFITS OF
FERMENTED DAIRY PRODUCTS
Nobel Laureate (1908) Elie Metchnikoff pioneered research
suggestingthat fermented milk has a beneficial value and reported
this in his theory of longevity (Amer and Lammerding,
1983). In vitro and in vivo studies on the functional properties
of fermented dairy products are ongoing, leading to further understanding
of the complexities of the product and the effect of
the product on human health.
Probiotics are live microorganisms that provide positive
healtheffects. Previous studies have indicated that fermented
dairy products can cause probiotic effects such as improvement
in digestive system health, serum cholesterol reduction,
improvement in lactose tolerance, improved immune function,
control of irritable bowel symptoms, as well as anticarcinogenic
properties. Some of the most prevalent beneficial probiotic
microorganisms have beenidentified as Bifidobacteria
species, Lactobacillus acidophilus, Lactobacillus plantarum,
Lactobacillus reuteri, Lactobacillus rhamnosus, Lactobacillus
salivarius, and Saccharomyces boulardii (Parvez et al., 2006;
Shah, 2007). Kefir made from kefir grains provides natural probiotics
mainly Lactobacillus acidophilus, Bifidobacterium bifidum,
many lactic acid bacteria, and yeast in high numbersAddress correspondence to Zeynep B. Guzel-Seydim, Department of Food
Enginnering, S¨uleyman Demirel University, C¸ ¨un¨ur, Isparta, 32260, Turkey. Tel.:
+90 (246) 211 1681; Fax: +90 (246) 237 1255. E-mail: zeyneps@sdu.edu.tr
(Kok-Tas, 2010) while people are seeking to develop functional
fermented dairy products.
Parvez et al. (2006) also reported that probiotic microorganisms
are most commonlyconsumed in the form of fermented
dairy products. Bioactive peptides and proteins from fermented
dairy foods also provide important health benefits such as stimulating
effects on lymphocyte proliferation and immunoglobulin
production, hypertension reduction, and increased absorption of
intestinal calcium (M¨oller et al., 2008).
The antimutagenic activity of fermented milk has been
reportedin various microbial and mammalian cell systems
(Hosono et al., 1986a; 1986b; 1990; Bodana and Rao, 1990;
Renner and Munzner, 1991; Hosoda et al., 1992; Nadathur et
al., 1995; 1996; Guzel-Seydim et al., 2006). Pool-Zobel et al.
(1993) determined that lactic acid bacteria have a high capacity
for binding mutagens.
Stidl et al. (2008) conducted a study on the ability of lactic
acid bacteria toreduce heterocyclic amines formed during
cooking of meat. The team noted overall reductions in heterocyclic
aromatic amine concentration by Lactobacillus helveticus,
Streptococcus thermophilus, Lactobacillus delbrueckii
subsp. bulgaricus, Bifidobacterium longum, Lactobacillus casei,
Lactobacillus acidophilus, Lactobacillus plantarum, and
Lactobacillus kefir were 83, 68, 59, 44, 42, 20,...