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Thursday, 1 December 2011

GROWTH-CYCLE of MILK KEFIR-GRAINS

Kefir grain micrograph 2,500X courtesy of M. KalabElectron Micrograph X 2,500 magnification of Kefir grains showing microflora of yeast and bacteria and polysaccharide matrix. Photo courtesy of Dr. Miloslav Kaláb with colour edited by Dominic N Anfiteatro to explain yeasts.
Traditional kefir grains of Caucasus is a fascinating natural mother-culture. Each granular body is formed through the effort of a dynamic, or symbiotic relationship shared among the complex microflora [bacteria and yeast], which render an irregular sheath, composed of protein, polysaccharide and lipid complex. The irregular fashioned sheath forms as a multiple irregular body with many lobules to create each kefir grain. I refer to these lobules as baby-grains, formed together as a mother-grain. The irregular lobules have a natural tendency to form as self-enclosed bio-structures or bodies, having a similar growth-signature to each other, with some variation between each baby-grain [see this picture]. The lobules are conjoined at a common midsection, radiating outwardly to form a mother-grain [a complete grain with all lobules attached]. On appearance, the growth pattern of conjoined baby-grains share self-similarity with the mother-grain, which it forms together as one body. Some kefir grains share similarity with the physical structure [morphology] of the brain, pancreas, and other internal body organs [those with an interest in Doctrine of Signature may find this of some interest].
After a period of time, and possibly due to external stress or physical trauma, one or more lobular bodies detach from any particular mother-grain. The smaller bodies, or baby-grains, eventually propagate into mother-grains, usually by increasing in overall size, with multiple lobular bodies forming over the entire grain. This growth-cycle simply repeats, to continue the ongoing process in a similar fashion. This is self-propagation. Some kefir grains may not shed any sections for some months, and in some instances for up to a year or longer. Such grains may instead form as one large structure or one massive kefir grain, retaining all lobular bio-structures. This can occur if the physical makeup of such grains is firm due to culture conditions, and if the grains are not subjected to hash physical trauma during the straining process e.g. In such cases, sections of baby-grains may be removed from a large mother-grain, by dissecting the grain by hand [see thisanimation for details of the operation].
Although in such cases, large kefir grains may eventually shed all attached bodies [or baby-grains] in a relatively short period. This is to say that the majority of attached bodies will spontaneously detach from mother-grains within a 2 month period, as a common example. This process occurs as each individual attached body's umbilical-like cord section attached to the mother-grain, reduces in circumference. Then, eventually, this section of the matrix becomes thin and weak, making conditions favourable for a baby-grain to spontaneously detach from the mother-ship, with ease. And if this process happens to all the attached lobular bodies in a relatively short period, then the specific batch of grains shall be comprised of numerous small kefir grains. In fact, weigh-for-weight, a batch of grains consisting of individual smaller grains may increase weight by 100% more efficiently than a batch made up of one large kefir grain, or overall larger grains. This may be due to a larger surface area that small grains make up [or take up in the media]. Or possibly that smaller grains produce and release larger proportions of kefiran into the milk, which becomes freely available for the microflora to create new matrix.
External surface area of each grain may vary from smooth areas, with areas of diverse irregularity, containing arrays of irregular small rounded protrusions randomly scattered over the exterior surface. The surface texture of certain grains may be smooth, while other grains from the same batch may exhibit a greater proportion of surface area covered with multiple irregular protrusions. Other grains from the same batch may exhibit a mixture of both surface-textures.
Flat kefir grainClick photo for larger view
Although less common, and mostly due to culture-conditions or the action of tearing an enclosed grain apart, kefir grains may propagate as an irregular flat sheath for some time at least. Also, mother-grains from a batch of enclosed grains, may propagate and then shed a baby-grain with a flat structure. These outcomes are mostly determined by culture-conditions, usually in warmer conditions, and if conditions are favourable, after a period of time, any flat grain[s] usually revert or transform into enclosed bodies, which seems a natural tendency for the fashion in which kefir grains grow in structure, under optimal or low stress conditions. Also, if an enclosed grain is torn apart by physical means, milk is allowed into the opening, which keeps the grain opened at the torn end. This forces the grain to grow flat, as shown in the photo. What ever the case is, such a transformation in growth may take some months to occur, and to complete the growth-transformation cycle, as flat grains grow to enclosed bodies.
I've observed batches of grains cultured in whole, raw goat or cow's milk, mostly propagate with smooth, well rounded lobular bodies [balloon-like], with daily milk changes. While kefir grains cultured in pasteurised milk and under cooler temperatures mostly propagate with many tiny protrusions covering most of the exterior surface of each grain. Seasonal changes [or temperature variation] may also incur a swing between one form of growth-structure to another. The type of medium, temperature and the amount of time that the grains are left in the same milk, including physical influence, such as tearing or cutting, all these factors have an effect on growth structure-activity of kefir grains. It appears however, that the physical structure of kefir grains does not impair the microflora's ability to culture.
Some observations suggest surface area of the grain consisting of vast irregularity or roughness, contain higher yeast activity. While smoother areas are mainly where bacteria predominate. Yeasts and bacteria cells, particularly yeasts, seem to form large surface concentration [micro-colonies] along the protrusions over the surface; streptococci seem to intertwine with other bacteria, without forming colonies. Research suggests internal structure of the grains show a predominance of Lactobacilli with few yeasts; cells are not bound to one another but encapsulated within a muco-polysaccharide believed to be produced by the encapsulated microorganisms.[11] Other research suggests stained sections of grains studied under a microscope, showed that yeasts were mainly located on the edge of the internal cavities, and occasionally along the peripheral channels of the matrix, while the exterior was mainly occupied by bacteria.[15]
Short and long rod-shaped bacteria and yeast, formed separate colonies both on the outside and inside of the grain. Internally, filaments of encapsulated cells, extending outwardly from a population of long rod-shaped bacteria. One microorganism in particular, Lb. kefiranofaciens is found to be responsible for the formation of the soluble polysaccharide, Kefiran. This research suggests that the encapsulated bacteria may be responsible for the propagation of kefir grains.[12] The reason for this conclusion seems to be because propagation of the grains will not occur [non-propagable grains] in the absence of Lb. kefiranofaciens, which produces kefiran in the centre of the grain, under anaerobic conditions and in the presents of ethanol alcohol.

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