Kefir Flashcards
describe kefir grains
white/yellow gelantinous grains
what is kefir composed of
symbiotic mixture of: lactic acid bacteria, yeast, acetic acid bacteria
what kind of matrix is kefir composed of in
exopolysaccharide matrix called (Kefiran)
kefir is… acidic or ?
acidic fermented milk product
name 2 methods of kefir production
- russian method
- the pure cultures
describe russian method
using a series fermentation process, beginning with the fermentation of the grains.
describe the Pure Cultures method
Isolated from kefir grains or commercial cultures.
what milks types of kefir made from
pasteurised cow, ewe, goat, or buffalo milk.
describe the 2 commercial industrial processing uses
direct to vat inoculation (DVI) or
direct to vat set (DVS) kefir starter cultures.
what ratio is grains to milk
grains usually innoculated at 1-10% w/v
time of fermentation
kefir obtained within 18-24 hr of fermentation.
kefir biomass increases and then may decrease (grains dissolve)
what temperature of kefir fermentation
18-30 degrees c.
exopolysaccharide production is affect by temperature
fermented kefir contains
bioactive peptides
bacteriocins
exopolysaccharides
organic acids.
briefly name challenges in kefir production
diverse microflora of kefir grain, milk type, incubation time and storage conditions.
describe kefir grains appearance
white to yellow gelantinous
what size kefir grains
variable. varying from 0.3–3.5 cm in diameter).
composed of microbial symbiotic mixture of
lactic acid bacteria
acetic acid bacteria
yeasts
fungi
in a polysaccharide matrix
what are the 4 main groups of kefir
- homo- fermentative LAB
- hetero -fermentative LAB
- lactose assimilating yeast
- non-lactose assimilating yeast
name bacterias
o Lactobacillus kefiri (80%; in final beverage)
o L. paracasei ssp. paracasei, L. acidophilus, L. delbrueckii ssp. bulgaricus, L. plantarum, and L. kefiranofaciens are predominant species (20% final beverage).
o Acetobacter aceti & A.rasens.
o S.cerevisiae, S.unisporus, Candida kefyr & Kluyveromyces marxianus sub sp. Marxianus
describe the polysaccharide in kefiran
heteropolysaccharide composed of equal proportions of glucose and galactose and is mainly produced by Lactobacillus kefiranfaciens
what is heteropolysaccharide composed of
equal proportions of glucose and galactose produced by Lactobacillus kefiranfaciens
what is heteropolysaccharide produced by
Lactobacillus kefiranfaciens
what does kefiran improve
viscosity and elasticity properties of acid milk gels and aids in gel formation
what causes the smybiotic balance of bacterias in equilibrium
biomass production during fermentation
the grain outer layer contains
LAB & yeast
the grain inner layer contains
the quantity of lactobacilli are much higher
describe the mechanisms of grain formation
symbiotic community where LAB, yeasts and AAB cohabit in a specific equilibrium
o This balance between kefir microorganisms is evident by biomass production during fermentation
the outer layer of the grain: LAB & yeast
The inner layer of the grain: the quantity of lactobacilli were much higher
Initially Lactobacillus & Saccharomyces start to auto-aggregate & co-aggregated into small granules this aggregation is enhanced when the pH drops
what do biofilm producers adhere to in grain formation
the surface. they continue to co-aggregate to become a 3D micro-colony.
list chemical % of kefir
90% moisture, 3.0% protein, 0.2% lipid, 6.0% sugar, 0.7% ash, 1.0% lactic acid, 0.48% alcohol and 201.7–277.0 mL/L CO2
microbial consortium is AKA
proteolysis
what role does yeast have in proteolysis
establishing an environment that allows for the growth of kefir bacteria, as well as the production of several key metabolites such as:
peptides, amino acids, vitamins, ethanol and CO2.
what key metabolites does yeast contain
peptides, amino acids, vitamins, ethanol and CO2.
what does lactic acid bacteria ferment/do in proteolysis
ferments the lactose to increase in lactic acid levels & as well as imparting the unique taste in kefir.
what does lactic acid inhibit
inhibits microorganism growth owing to decrease in pH acting as a preservative.
free fatty acids FFAs produced via… and what is it responsbile for
lipolysis in milk are responsible for the taste and aroma of kefir which was found to contain from 5 to 10 times more FFAs than milk.
name amino acids in kefir and what role do they play
serine, threonine, alanine, lysine, valine, isoleucine, methionine, phenylalanine and
tryptophan.
major role in central nervous system
name macro-elements in kefir and what role do they play
calcium, magnesium, potassium, and sodium
that aid in the: utilisation of carbohydrates, fats and proteins for cell growth, maintenance, and energy
name micro-elements in kefir and what role do they play
iron, zinc, and copper
: cellular metabolism and blood production
kefir acts against what bacteria and what does it do
pathogenic bacteria.
inhibits spore formation and aflatoxin B1 produced by the fungus Aspergillus flavus
name health benefits of kefir
- antioxidant
- antimicrobial
- gastrointestinal function
- cholesterol lowering
- reduced bodyweight
- anti-inflammatory
- anticancer
- probiotic
- wound healing
Conjugated linoleic acid (CLA)
native component in milk fat, can be increased in fermented milk through bioconversion of unsaturated fatty acids such as linoleic and linolenic acids by different LAB.
CLA has anti-inflammatory, anti-atherogenic, and antioxidant properties.
Bioactive peptides
are specific fragments of milk proteins that are released by proteolytic activity from caseins have been described for peptides released as a result of the activity of LAB in fermented milk products.
what role does Bacteriocins do
are also among the beneficial peptides intrinsically synthesised by some LAB and their usefulness in preventing growth of undesirable & pathogenic microorganisms
role of Extracellular PolySaccharide(EPS):
are complex extracellular carbohydrate polymers +ve interact with colonic microbiota
