Impact of environmental factors on the metabolic profiles of Kefir produced using different Kefir grains and subsequent enrichment of Kefir prepared with mass cultured grains
Year: 2012
Type: article
Abstract: The fermentation of milk has been known for millennia and leads to nutritious and prolonged shelf-life dairy products.In Southern Africa, traditional fermented dairy products have the same value as local staple foods and are consumed as a part of or as a whole meal.However, the retail price and the technology make many commercialised fermented dairy products unaffordable to the majority of the population.There is thus a need for a healthy nutritious low-cost easily prepared fermented dairy product.A product that could be the answer to the above need, is Kefir.The principle advantage is that the Kefir beverage is made from reusable Kefir grains, which unfortunately are not easily available and grow slowly.Kefir grains can only be obtained from pre-existing grains, which presents a problem in the marketing of the grains.A mass culturing technique was developed to produce large masses of grains but preparation of Kefir using these grains results in a product (MG Kefir) lacking in the sensory attributes of Traditional Kefir.Thus, the overall objective of this research was to determine the impact of environmental factors on the metabolic profiles of Kefir produced using different Kefir grains and this was then followed by the subsequent enrichment of Kefir prepared with mass cultured grains so as to obtain a Kefir beverage that has improved organoleptic qualities.To determine the impact of environmental factors Traditional and MG Kefir were prepared under controlled and uncontrolled conditions.Traditional Kefir was found to give the best beverage and was thus considered as the control.Under controlled conditions the optimum incubation temperature for the production of Kefir was 22ºC as over-acidification was observed at 25ºC.The metabolic profiles of both Traditional and MG Kefir showed that both contained acetaldehyde, ethanol, acetone, diacetyl and acetic acid.In addition, the metabolic profiles revealed that an inadequate ratio of diacetyl to acetaldehyde as well as the lack of ethyl acetate was responsible for the flavour defect in MG Kefir.In order to overcome this defect, citrate and ascorbate (0.015 % w.v -1 ) were added during Kefir fermentation to enhance the diacetyl and ethyl acetate production.This addition showed a positive impact on diacetyl but not on ethyl acetate production.Improvement of the overall flavour of Kefir was observed as the ratios of diacetyl to acetaldehyde were higher (0.21 -0.5) in the samples with added citrate and ascorbate than in the samples without (0.12 -0.17).The production of ethyl acetate in MG Kefir was enhanced by combining the effects of longer incubation (24 h + 18 h at 22ºC), addition of ethanol and acetic acid at 0.79% (m.v -1 ) and the addition of either Lactococcus lactis ssp.diacetylactis biovar diacetylactis 318 or Candida kefyr 1283.The best yields were obtained in samples containing C. kefyr 1283 and only added ethanol (9.22 mg.L -1 ), indicating that ethanol is an important factor in ethyl acetate production by Kefir starter strains and Stellenbosch University http://scholar.sun.ac.za (RPD = 2.57 -3.16), pH (RPD = 2.90) and TA (RPD = 2.60) were good for screening purposes (2 < RPD < 3); indicating that these models would show if the concentrations of lactic acid, the pH or the TA varied from the normal range.This study has demonstrated that the flavour of MG Kefir, prepared with enriched grains, was successfully improved and has provided some understanding on the preference liking of Kefir, an unknown fermented dairy product to South African consumers.
Authors: Ntsame Affane, Armelle Lyvane
Language: English
Subfield: Food Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
Funder: National Research Foundation
OpenAlex ID: W1922533898