The citrate metabolism has been extensively studied in lactic acid bacteria (LAB) for its aroma compound production. Among the 4-carbon (C4) by-products obtained from citrate fermentation, diacetyl is one of the better known products for its contribution to the buttery aroma of dairy products. A lot of documents deal with ways to improve diacetyl concentration in food matrices. Apart from these organoleptic advantages, in a microbial ecosystem, the citrate metabolism gives selective advantages to citrate positive microorganisms. Citrate metabolism allows the LAB to use another carbon source for their growth, withstand acidic conditions and generate a "proton motive force" (PMF). Moreover, the citrate/glucid co-metabolism leads to the fast release of organic compounds known for having bacteriostatic effects. Under specific conditions, the C4 pathway liberates diacetyl which is bacteriostatic. In this review we first describe the citrate metabolism and the enzymes involved in the two homo-and heterofermentative LAB Lc diacetylactis and Leuconostoc spp. Moreover, the way to shift the metabolic pathway toward the production of aromatic compounds is discussed for both of these fermentative types of bacteria. Finally, the selective advantages of citrate metabolism for LAB in complex microbial ecosystems are delineated.

Traditional (solar) drying of okra fruits (Abelmoschus esculentus L. Moench) often gives products of poor storage quality, short shelf life and unpleasant sight. This study assesses the suitability of a dewatering-impregnationsoaking process (DISP) and blanching prior to drying as a means of improving the stability and the appearance of the dried okras. The DISP/Blanching pre-treatment involved immersing whole okra fruits for 12 hrs in a warm concentrated osmotic solution (made of NaCl, ascorbic acid, citric acid and "kanwa") that was progressively cooled from 85°C to room temperature (~ 24°C), before drying at 40°C. Compared to simple blanching, the DISP/Blanching pre-treatment yielded dry products that were better appreciated both to the touch and to the sight. The combined DISP/Blanching and drying process gave averages of (78.1 ± 3.6) % weight reduction, (9.1 ± 0.5) % solute gain and (87.2 ± 4.0) % water loss. The total water loss was due at 35.6 % to the DISP/blanching pre-treatment and at 64.4 % to the further drying process. The results obtained here demonstrate the possibility of improving the storage quality of dried okra through the combined DISP/Blanching pre-treatment, reducing post-harvest losses and improving the market quality of dry products. This treatment could be applied industrially to enhance the presentation of tropical vegetables in international markets.