No abstract

Artisanal mezcal is produced by the natural fermentation of maguey juice, which frequently results in a process that becomes stuck or is sluggish. Using selected indigenous starter inoculums of Saccharomyces and non-Saccharomyces yeasts is considered beneficial in overcoming these problems and thereby preserving the essence of the artisanal process. In this work, three hundred and four yeast isolates were recovered from 17 distilleries and then grouped by the ARDRA analysis, their restriction profiles were clustered in 15 groups. Four of them included 90% of all isolates, and these were identified using the sequence of the D1/D2 domain of the large-subunit rDNA. Pichia kudriavzevii, Pichia manshurica, Saccharomyces cerevisiae, and Kluyveromyces marxianus were detected as predominant species. Both species belonging to the Pichia genus were detected in 88% of the distilleries, followed by S. cerevisiae (70%) and K. marxianus (50%). In order to evaluate the fermentative capacity, one strain of each species was assessed in a pure and mixed culture in two culture media, filtered maguey juice (MJ) and maguey juice including its bagasse (MJB). Findings demonstrated that non-Saccharomyces yeast presented better growth than that of S. cerevisiae. K. marxianus PA16 was more efficient for ethanol production than S. cerevisiae DI14. It produced 32 g/L of ethanol with a yield of 0.47 g/g and efficient of 90%. While, P. kudriavzevii produced more ethyl acetate (280 mg/L) than the others species. All fermentations were characterized by the presence of isobutyl and isoamyl alcohol. The presence of K. marxianus in a mixed culture, improved the ethanol production and volatile compounds increased using co-cultures.

The aim of this study was to isolate and identify the yeasts present in taberna, a traditional palm wine from Mexico, which is produced by natural fermentation of the palm sap obtained from Acrocomia aculeata. A total of 450 yeast isolates were obtained from 45 taberna samples collected over 15 days of tapping at the end of fed-batch fermentation (12 hours of feeding and fermentation of the sap in the canoe) from three coyol palm trees. The yeast isolates were identified using restriction pattern analysis of the internal transcribed spacer region 5.8S-ITS and by sequence analysis of the D1/ D2 divergent domain of the 26S rRNA gene. Nine different yeast species were identified in the taberna samples tested, namely, Saccharomyces cerevisiae, Hanseniaspora guilliermondii, Candida tropicalis, Candida intermedia, Kazachstania unispora, Kazachstania exigua, Meyerozyma guilliermondii, Pichia kudriavzevii (Issatchenkia orientalis) and Pichia kluyveri. The non-Saccharomyces yeasts H. guilliermondii and C. tropicalis were detected in samples from all three palm trees, while S. cerevisiae was detected in samples from only two of the palm trees. The frequency and distribution of the yeast species were different in the samples of each palm tree, which indicated that the inoculum in the palm sap may be deposited randomly by different vectors. This study is the first to characterize the yeast population associated with the palm wine named taberna.

In this article, the effect of direct solar drying, indirect solar drying, and freeze drying on the phenolic compound contents and antioxidant capacities of blackberry fruits was investigated. The solar drying kinetics were determined and fitted to six thin layer different mathematical models. The total phenolic, anthocyanin, and flavonoid contents as well as the antioxidant capacity based on ABTS, DPPH, and OH• assays were determined for the dried blackberry samples. The results show that the Midilli–Kuçuk model provides the best fit to the experimental data of solar drying in both methods tested. Greater antioxidant capacities were observed in the samples dried by using direct solar drying method in all experiments, that is, the ABTS, DPPH, and OH• activities were 36,757 ± 1.27; 21.120 ± 1.33, and 47 ± 7.31 μmol TEAC/g dm, respectively. The creation of compounds during food dehydration at moderately high temperatures can enhance the antioxidant capacities and phenolic contents. Practical applications Rubus fruticosus is a berry with nutraceutical potential by the presence of bioactive compounds. The removal of water from a fruit extends the conservation time of the product during storage and transportation, facilitating the access to such foods when required. One of the most economical and sustainable ways to do the drying is to use solar dryers. Direct and indirect solar drying are technologies that have effects that must be taken into account according to the food that is to be dried and the final characteristics that are desired to obtain. However, the phenolic compounds present in the fruit are sensitive to the thermal process. Thus, it is important to know its consequences phenolic compounds and antioxidant activity for better use of the fruit.

In this study, 19 indigenous mezcal Saccharomyces cerevisiae strains were screened for their tolerance to grow under different stress conditions and their potential use in fermentation. All strains were able to tolerate pH value of 3, significant levels of glucose (30%), ethanol (12% v/v), and temperature of 37°C. Eleven of them were able to grow in presence of 15% of ethanol, but only CH7 and PA18 strains grew at 42°C. Both were selected for evaluation of their fermentative abilities in maguey juice and in a synthetic medium incubated at 30 and 40°C. Temperature of 40°C had a positive effect on the ethanol production, increasing the productivity and efficiency in maguey fermentation. Ethyl acetate, isobutanol and isoamyl alcohols production was favored at 30°C. Both evaluated strains presented a good fermentative capacity and production of volatile compounds, suggesting their potential use as starter cultures in mezcal fermentation.