Zymological indicators: a new concept applied to the detection of potential spoilage yeast species associated with fruit pulps and concentrates

Abstract

In a survey of the microbial quality of raw materials used in fruit juice processing, yeast counts in fruit concentrates and pulps were found to range from 51to 2?9610 3 cfu g 71. Ascomycetous yeasts were represented by 76% of the isolates while 24% were basidiomycetes.The identi¢cation of strains isolated by the simpli¢ed identi¢cation system (SIM) revealed19 yeast species representing12 genera.The most frequently isolated yeasts belonged to the genera Saccharomyces, Pichia, Cryptococcus, Kluyveromyces and Candida. Fatty acid yeast composition allowed the separation of contaminating yeasts into one of three major groups. Group I included yeasts without linoleic (C 18:2) and linolenic (C 18:3) fatty acids such as Saccharomyces cerevisiae. Group II comprised yeasts without C 18:3 fatty acid like Zygosaccharomyces rouxii and Torulaspora delbrueckii, and group III included yeasts with C 18:2 and C 18:3 acids that belong, among others, to one of the following yeast genera: Pichia, Candida, Kluyveromyces or Cryptococcus. Species-speci¢c PCR primers were used for the rapid detection and identi¢cation of the most dangerous species a¡ecting fruit concentrate stability. The simpli¢ed protocol used consisted of PCR-ampli¢cation of conserved tracts in the ITS region of the rDNA unit, thus enabling the detection of potentially dangerous £ora such as Zygosaccharomyces species andT. delbrueckii in contaminated fruit concentrates. Results from PCR-typing were in full agreement with the fatty acid compositions of these species. The grouping of contaminant yeasts into three main groups showed that fatty acid composition may be used to di¡erentiate yeasts according to their technological signi¢cance.Yeasts isolated in this work as being most dangerous to product stability belong to either group II (Z. rouxii and T. delbrueckii) or group I (Saccharomyces spp.). Group III was comprised of several species regarded as indicators of de¢ciencies in 'good manufacturing practices'. Thus, each of the groups delineated may be considered to be a zymological indicator of technological signi¢cance. The conjugation of fatty acid pro¢les with PCR-typing methods may be used as a rapid detection system for contaminant yeasts. The fatty acid pro¢les provide a preliminary identi¢cation of yeasts potentially dangerous to product stability present

Yarrowia lipolytica: Safety assessment of an oleaginous yeast with a great industrial potential

“…For instance, Y. lipolytica has been detected in other fermented food products, such as tempeh and sourdough (Romano et al, 2006;Samson et al, 1987), in soft drinks, juices, wine, must and cider (Stratford, 2006), in fruits, fruit concentrates, vegetables and raw plant materials (Sancho et al, 2000), in mayonnaise, salad dressings and salads (Baleiras Couto et al, 1996), as well as in chilled and frozen, processed food, including seafood. All these examples suggest that Y. lipolytica may be a regular, although probably minor, component of food microbiota.…”

Estudio del proceso biotecnológico para la elaboración de una bebida alcoholica a partir de jugo de naranjas.

“…Sin embargo las pruebas fisiológicas y bioquímicas siguen siendo desarrolladas y usadas. Así, los métodos de identificación simplificados (SIM) adaptados y publicados por Deak and Beuchat, 1996, fueron recientemente muy bien empleados para levaduras aisladas de jugos de frutas (Sancho et al, 2000). Velásquez et al,(2001) presentaron un sistema para la identificación de levaduras en productos alimenticios, mediante el uso de kit de 10 pruebas para levaduras vínicas.…”

Identifying yeast isolated from spoiled peach puree and assessment of its batch culture for invertase production

“…Both are urease positive (Table 1, Figure 1), which matches Chen et al (2010) for the urea hydrolysis test. Beckenkamp (1997), when working with pasteurized fruit pulp samples, also identified the genera Rhodotorula & Trichosporon, while Sancho et al (2000) identified R. mucilaginosa in pear pulp. Guamán-Burneo & Carvajal-Barriga (2009), while working with different yeasts species of the genus Rhodotorula, found different salmon and pink hues for R. mucilaginosa cultured in CPM agar for 72 h at 20, 30, and 37 °C.…”

“…This enzyme has been long known and many consider the activity in the batch culture supernatant, here called CI, an extracellular invertase, including invertase from A. parasiticus (Lucca et al, 2013), from A. ochraceus (Guimarães et al, 2007), and from Penicillium chrysogenum (Poonawalla et al, 1965). According to Myers et al (1997), the expression of the gene that codes invertase is repressed at high free glucose concentrations. In this research, high free glucose concentration was only observed in the beginning of the log phase, which may be related to the low CI activity observed after 24 h of fermentation (Table 2).…”

“…Moreover, they are ubiquitous eukaryote microorganisms with an active role in fermented foods, pulps, and drinks (Fazio, 2006;Silva et al, 2011). In fruit pulps, the most commonly isolated yeasts belong to the genera Saccharomyces, Pichia, Cryptococcus, Kluyveromyces, and Candida (Sancho et al, 2000;Melo et al, 2007;Aleklett et al, 2014).…”