Estudio microbiológico comparativo de la fermentación industrial de alcaparrones en la provincia de Jaén

Resumen

Caper is a native Mediterranean plant whose distribution stretches from the Atlantic coasts of the Canary Islands and Morocco to the Black Sea, Crimea and Armenia, and eastward to the Caspian Sea and into Iran. Traditional fermented caper berries are highly appreciated for their unique organoleptic properties in the South of Spain. Over centuries fermentation has taken place in households and only for private consumption. However, in the last decades, a few local pickles enterprises have been maintaining a small production with a very limited but popular distribution. Caper fruit market is growing and a microbiological characterization has become essential. Our objective was to characterize local industrial caper fruit fermentation as it is commercialized in the South of Spain. Representative samples from SMEs were studied by culture-dependent and independent methods during two consecutive harvest seasons. Small differences could be detected between different SMEs regarding their characteristics and sensorial analysis. Microbial counts showed that yeasts were present in almost all samples, followed by lactic acid bacteria. RAPD-PCR of a collection of 115 isolates showed a strong genetic relatedness among isolates from different sources (SMEs). All bacterial isolates identified as Lactobacillus plantarum by sequencing of pheS and rpoA genes showed different technological properties. Similarly, a cultureindependent analysis of fermentation samples by Denaturing Gradient Gel Electrophoresis (DGGE) also indicated that Lb. plantarum was the predominant species in this fermentation. Furthermore, yeasts and molds were represented by Pichia membranifaciens and Geotrichum sp. as the main yeast species in almost all SMEs. During the two-year study, industrial caper berry fermentation has shown to be uniform and safe from the microbiological point of view. However, this natural fermentation is usually carried out by a traditional process relying on the indigenous microbiota. To ensure quality and safety of the end product producing a uniform and homogeneous fermented caper berries which could open new international markets for unknown local products with a high nutritional and safety values, the application of Lb. plantarum isolated from spontaneous caper berry fermentation as starter culture could be a good alternative. The starter-added fermentation with a Lb. plantarum Lb9 strain selected according to its functional properties was evaluated by means of culturedependent and independent methods. The results obtained here indicated that Lb. plantarum Lb9 was able to carry on an accelerated lactic acid fermentation of caper berries dominating the background microbiota present in the raw material until the end of fermentation even when fermentation broth was added with high salt concentration. The persistence of L. plantarum Lb9 in the starter-added fermentation was confirmed by RAPD-PCR of the dominating colonies. TTGE analysis of the microbial community throughout fermentation process also indicated that Lb. plantarum was the predominant bacterial species in the fermentation. Furthermore, the sensorial quality of the starteradded fermented capers was similar to the spontaneous fermented products. In conclusion, L. plantarum Lb9 was an adequate starter culture strain for caper berry fermentation prevailing over other bacteria present in the raw material. This fermentation ensured both the quality and safety of the end product.