Influence of controlled inoculation of malolactic fermentation on the sensory properties of industrial cider

Given the lack of research in the traditional cider making field when compared to the efforts devoted to winemaking, this work focused on the effects of controlled inoculation of the malolactic fermentation (MLF) on the sensory properties of cider. MLF develops spontaneously in cider making at industrial level. In this work, industrial cider samples were inoculated with selected indigenous Oenococcus oeni strains and the benefits on the aroma and flavour in cider production compared to non-inoculated ciders were evaluated. Randomly amplified polymorphic DNA PCR was used to monitor strain colonization ability, outnumbering the indigenous microbiota, after completion of the alcoholic fermentation at industrial scale (20,000 l). Aroma-active compounds of experimentally inoculated ciders were analysed by HPLC and GC-MS, and sensory profiles were determined by fractioning aroma extracts using reversed-phase HPLC. Principal component analysis allowed the identification of relationships and differences among ciders with or without inoculation, including several highly appreciated commercial ones obtained under spontaneous conditions. Under controlled inoculation conditions, not only could MLF be shortened by half but, interestingly, enhancement of aroma complexity and flavour resulted in ciders enriched with a higher fruity note. In addition, important aromatic groups analysed here had not been previously described, thus affording deeper knowledge on aroma characterization of apple cider.