Combined approach for the investigation of dominant fermenting microbiota in two traditional sourdoughs produced in sicily

In order to explore the community of lactic acid bacteria (LAB) and yeasts present in two major typical Sicilian sourdoughs, seven mature sourdoughs for "Pane Nero di Castelvetrano" (CV1 - CV3 samples) and "Pane di Monreale" (MR1 - MR4 samples) were analysed through a culturedependent and culture-independent approach. The highest values of microbial counts were revealed in MR1 sourdough. In particular, LAB counts were at about 109 CFU/g in media specific for typical sourdough LAB, such as SDB and SFM, while levels of 106 CFU/g were registered for yeasts. The total DNA form each sourdough sample was extracted and subjected to a multiplex-PCR in order to recognize the major groups of LAB. Seventy-six LAB with a rod shape, presumptively Lactobacillus, were phenotypically grouped and subjected to a genotypic identification by sequencing of the 16S rRNA gene and further confirmed by species-specific PCRs. Yeasts were isolated and identified by a combined genotypic approach consisting of restriction fragment length polymorphism (RFLP) of 5.8S rRNA gene and sequencing of D1/D2 domain of the 26S rRNA gene. The LAB species identified were Lactobacillus sanfranciscensis, Lactobacillus paralimentarius, Lactobacillus brevis and Lactobacillus coryniformis. Among yeasts, Saccharomyces cerevisiae, Pichia guiliermondii, Pichia segobiensis, Rhodotorula acuta and Rhodotorula mucilaginosa were the species hosted in Sicilian sourdough. The multiplex PCR carried out on total DNA of sourdoughs allowed the rapid identification of the majority of sourdough lactobacilli but the culture-dependent methodology was confirmed to be necessary for the detection of the species, such as Lactobacillus coryniformis not included in the system

Design and implementation of a smart system to control aromatic herb dehydration process

Drying is a process aimed at reducing the water content in plant materials below a limit where the activity of microbes and decomposing enzymes deteriorate the quality of medicinal and aromatic plants. Today, the interest of consumers towards medicinal and aromatic herbs has registered a growing trend. This study aims at designing a low-cost real-time monitoring and control system for the drying process of aromatic herbs and evaluating drying ecacy on the microbial community associated with the studied herbs. Hot-air drying tests of sage and laurel leaves were carried out in a dryer desiccator cabinet at 40 C and 25% relative humidity using three biomass densities (3, 4 and 5 kg/m 2 ). The prototype of the smart system is based on an Arduino Mega 2560 board, to which nine Siemens 7MH5102-1PD00 load cells and a DHT22 temperature and humidity sensor were added. The data acquired by the sensors were transmitted through Wi-Fi to a ThingSpeak account in order to monitor the drying process in real time. The variation in the moisture content of the product and the drying rate were obtained. The system provided a valid support decision during the drying process, allowing for the precise monitoring of the evolution of the biomass moisture loss and drying rate for laurel and sage. The three dierent biomass densities employed did not provide significant dierences in the drying process for sage. Statistically significant dierences among the three tests were found for laurel in the final part of the process. The microbial loads of the aromatic herbs after drying were influenced by the dierent leaf structures of the species; in particular, with laurel leaves, microbial survival increased with increasing biomass density. Finally, with the drying method adopted, the two species under consideration showed a dierent microbial stability and, consequently, had a dierent shelf life, longer for sage than laurel, as also confirmed by water activity (aw) values

Microorganisms of food ice cubes and their transfer to drinks

The present work was carried out to investigate the microbiological characteristics of the ice cubes produced at different levels: 1) home-made (HM) from domestic freezers; 2) produced by ice machines in bars and pubs (BP); 3) produced by ice industries (IN). BP samples were collected from the box stocks. HM and BP samples were transferred into sterile stomacher bags. IN samples were provided in the manufacturers’ plastic bags. Samples were transported into thermal insulated boxes. Five samples per each production level, forming a total of 15 samples (HM1-HM5, BP1-BP5, IN1-IN5), were collected in duplicate in two consecutive months. Each ice sample was thawed in 1 L sterile Dhuram’s bottle at room temperature and subjected to the membrane filtration analyses. Total mesophilic microorganisms (TMM), total psychrotrophic microorganisms (TPM), pseudomonads, members of the Enterobacteriaceae family, coliforms, enterococci, yeasts and moulds were investigated. When the amounts of colonies were uncountable, 1 mL of sample was directly inoculated into agar media. All results were expressed as colony forming units (CFU)/100 mL of thawed ice. TMM were in the range 100-9600, 312-6300 and 130-4000 for HM, BP and IN samples, respectively. Three HM and two IN samples were negative for the presence of TPM. The highest concentration (960) was found for IN2. Pseudomonads were detected in all HM samples but the highest levels were registered for BP1 (390) and IN2 (384). Except IN4, Enterobacteriaceae were found in all samples. All INs and 4 HM samples did not displayed coliforms. By contrast, they were hosted in all BP samples, ranging from 1 to 184. Enterococci were never found in HM samples, but detected in two INs and 3 BPs. Except IN1, moulds were always registered, while yeasts developed from the majority of HM and IN samples and two BP samples. The colonies representative for the different morphologies were randomly picked up from plates, purified to homogeneity and subjected to a phenotypic grouping. Yeasts and bacteria were subjected to the genetic identification by sequencing of D1/D2 domains of 26S rRNA gene and partial sequencing of 16S rRNA gene, respectively, while moulds were identified phenotypically. So far, the species mostly represented among bacteria, as evaluated only by the forward 16S rRNA gene sequence, were Bacillus spp., Pseudomonas spp., Pantoea spp., Pantoea agglomerans, Enterococcus faecium, and Agrobacterium tumefaciens. Candida intermedia and Pichia guillermondii were identified among yeasts and Penicillium spp. among moulds. The work was also aimed to monitor the microbial transfer from ice to humans through drinks. To this purpose, each microorganism was inoculated singly in sterile mineral water to produce contaminated ice cubes using disposable ice cube trays. Inoculums occurred at the highest concentrations found in the ice cubes analysed. The concentrations of the microorganisms were followed in six different types of drinks, including alcoholic (vodka and whiskey), moderate alcoholic (Martini), sparkling (tonic water), sugary (peach tea) and sugary sparkling (coke) drinks. In order to simulate the contamination of drinks by ice during consumption, six ice cubes (corresponding to 60 mL) containing each microorganism were added to 100 mL of each drink (simulating a bar administration) in sterile cups and, after 1 h, the entire volume was analysed by membrane filtration. A physiological solution was used as control. So far, the tests were performed with Penicillium spp. and P. agglomerans. Penicillium was not influenced by the different drinks, since, after 1 h, its level did not change. Regarding P. agglomerans, which is an opportunistic pathogen causing urinary tract infections, its concentration in peach tea was superimposable to that found in physiological solution, while it decreased in all other drinks. In particular, the concentration of this bacterium almost halved in vodka, coke and tonic water, diminished consistently in Martini and completely disappeared in whiskey. Experimentations are in progress to determine the behaviour of the other microorganisms in these systems. These data evidenced that the worst hygienic characteristics were found in BP samples, while the majority of ice cubes produced in specialized industries were characterized by acceptable microbiological parameters. This work indicated that the concentration of P. agglomerans is reduced by alcohol and CO2, but further in vivo assays are necessary to better clarify their role on the other ice microorganisms

Selected lactic acid bacteria as a hurdle to the microbial spoilage of cheese: application on a traditional raw ewes’ milk cheese.

To evaluate the efficacy of lactic acid bacteria (LAB) to improve the hygienic safety of a traditional raw milk cheese, the raw ewes’ milk protected denomination of origin (PDO) Pecorino Siciliano cheese was used as a model system. Different Pecorino Siciliano curds and cheeses were used as sources of autochthonous LAB subsequently used as starter and non-starter LAB. These were screened for their acidification capacity and autolysis. Starter LAB showing the best performance were genotypically differentiated and identified: two strains of Lactococcus lactis subsp. lactis were selected. From the nonstarter LAB, Enterococcus faecalis, Lactococcus garvieae and Streptococcus macedonicus strains were selected. The five cultures were used in individual or dual inocula to produce experimental cheeses in a dairy factory for which production was characterised by high numbers of undesirable bacteria. At 5- month of ripening, the experimental cheeses produced with LAB were characterised by undetectable levels of enterobacteria and pseudomonads and the typical sensory attributes

Effects of Tray-Drying on the Physicochemical, Microbiological, Proximate, and Sensory Properties of White- and Red-Fleshed Loquat (Eriobotrya Japonica Lindl.) Fruit

Loquat fruits, highly valued by consumers for their characteristic aroma and pleasant taste, have a short post-harvest life and are susceptible to mechanical damage, loss of firmness, and initial organoleptic characteristics. The aim of this work was to develop a drying method suitable for storing loquat fruits in polyamide/polyethylene (PA/PE) bags containing two gaseous mixtures (treatments): MAPN2 (100% N2) and MAPP (21% O2 and 0.04% CO2), at room temperature for at least 2 months. The effects of these conditions on the physico-chemical, microbiological, proximate, and sensory properties of fruit stored over a 50-day time interval were studied. The results showed that convective tray dehydration treatment at 70 for 12 h had good drying efficiency for loquat slices. In addition, the MAPN2 packaging limited the browning of the slices, keeping the microbial groups below the detection limits, with a clear positive effect on some minerals and vitamins, which were higher in concentration compared to the MAPP-packed samples. From an applicative point of view, the tray drying method for loquat fruits is useful on a small scale but could also be easily industrialized

Effect of the wooden vats on traditional cheese characteristics

Wooden vats have been used for centuries to collect and transform milk by farmers and cheesemakers all over the world. Nowadays, the tree species mostly used to this purpose are Douglas fir and chestnut. The use of wooden vats is mandatory for the production of all PDO Sicilian cheeses, such as Ragusano, Pecorino Siciliano, Piacentinu Ennese and Vastedda della valle del Belìce. In the last years, the wooden vats have been deeply explored for the microbiological characteristics and they are covered by biofilms mainly represented by lactic acid bacteria (LAB) entrapped in a polysaccharide matrix. These microbial associations do not include pathogenic species. Up to date, there are no studies performed on the effect of wooden vats made with different tree species on the characteristics of the final cheeses. Thus, this aspect represents the main aim of the present study. Eight wooden vats (20-L volume) were made with eight tree species (Calabrian Chestnut, Sicilian Chestnut, Cedar, Cherry, Ash, Wot, Pine and Poplar) and subjected to 15-d whey treatment for the activation of the LAB biofilms on the internal surfaces. All 8 wooden vats were then used to produce PDO Vastedda della valle del Belìce cheese, according to the EU Regulation. Each cheese making (carried out in duplicate at 7-d interval) was obtained from 14 l of raw ewes’ milk. The cheeses were packaged under vacuum and, after 14 days of refrigerated storage, analysed for their physical (pH, aw, CIELab parameters) and chemical composition (DM, fat, protein, N soluble, ash, salt) according to official methods. Moreover, peroxides, TBARs and polyphenols were also determined. Vastedda cheeses were subject to a sensory evaluation following the ISO indications. Several ANOVA models were employed to statistical analyses. The results of the characterization of the cheeses revealed that the wooden vats did not influence their chemical composition, while Lightness (L*) and hue angle were significantly modified by the tree species (table 1). In particular, the cheeses produced in vats made with Calabrian and Sicilian chestnut were characterized by a lower yellow intensity than the other tree species. Poplar vat produced Vastedda cheeses with significant lower peroxidase oxidation (1.68 mq/kg) and TBARs (0.0042 mg MDA/100 g of fat), probably due to the effect of natural antioxidant transferred from the wood to the milk. No particular differences among cheeses were appreciated by the panellists

Shelf life evaluation of fresh-cut red chicory subjected to different minimal processes

Microbiological, chemical and physical parameters of minimally processed red chicory (Cichorium intybus L.) subjected to two different transformation processes were investigated. A classic ready-to-eat (RTE) process (P1) and a production without cutting (P2) were monitored during refrigerated (4 °C) storage (15 d). Total mesophilic microorganisms, total psychrotrophic microorganisms and pseudomonads were detected at the highest cell densities in all samples. Presumptive Pseudomonas population dominated the cultivable microbial community of RTE red chicory and were characterized genetically. Twenty-two randomly amplified polymorphic DNA (RAPD) types were investigated by 16S rRNA gene sequencing, resulting in members of Rahnella and Pseudomonas. The identification of Pseudomonas species was further determined by sequencing of gyrB, rpoB and rpoD genes resulting in 16 species. A highest visual quality and a lower weight loss and colour variation were registered for P2, while soluble solid, nitrate and ascorbic acid contents were not affected by processing and storage. The integrated microbiological, chemical and physical approach applied in this study demonstrated the longer shelf-life of P2 red chicory

A Functional End-Use of Avocado (cv. Hass) Waste through Traditional Semolina Sourdough Bread Production

In recent years, a main goal of research has been to exploit waste from agribusiness industries as new sources of bioactive components, with a view to establishing a circular economy. Non-compliant avocado fruits, as well as avocado seeds and peels, are examples of promising raw materials due to their high nutritional yield and antioxidant profiles. This study aimed to recycle avocado food waste and by-products through dehydration to produce functional bread. For this purpose, dehydrated avocado was reduced to powder form, and bread was prepared with different percentages of the powder (5% and 10%) and compared with a control bread prepared with only semolina. The avocado pulp and by-products did not alter organoleptically after dehydration, and the milling did not affect the products' color and retained the avocado aroma. The firmness of the breads enriched with avocado powder increased due to the additional fat from the avocado, and alveolation decreased. The total phenolic content of the fortified breads was in the range of 2.408-2.656 mg GAE/g, and the antiradical activity was in the range of 35.75-38.235 mmol TEAC/100 g (p < 0.0001), depending on the percentage of fortification

Optimised method for the analysis of phenolic compounds from caper (Capparis spinosa L.) berries and monitoring of their changes during fermentation

In this work, an ad hoc method to identify and quantify polyphenols from caper berries was developed on high-performance liquid chromatography/electrospray ionisation source/mass spectrometry (HPLC-ESI-MS). The method was applied during fermentation carried out with Lactobacillus pentosus OM13 (Trial S) and without starter (Trial C). A total of five polyphenols were identified. All samples contained high concentrations of rutin. Epicatechin was found in untreated fruits, on the contrary quercetin was detected during fermentation. Trial S was characterised by a more rapid acidification and lower levels of spoilage microorganisms than Trial C. L. pentosus dominated among the microbial community of both trials and the highest biodiversity, in terms of strains, was displayed by Trial C. Aureobasidium pullulans was the only yeast species found. The analytical method proposed allowed a high polyphenolic compound recovery from untreated and processed caper berries in short time. The starter culture reduced the bitter taste of the final product