Application of nine air-dried Capsicum annum cultivars as food preservative: Micronutrient content,antioxidant activity,and foodborne pathogens inhibitory effects

Capsicum annum cultivars Yellow cayenne, Portafortuna, Idealino, Sole, Duemila, Pellegrino, Fantasia, Loco, and Effix were investigated for their antioxidant properties and foodborne pathogens inhibitory activity. The total phenols, flavonoids, anthocyanins, capsaicinoids, carotenoids, ascorbic acid, and vitamin E content were also determined. Duemila and Portafortuna cultivars showed the highest total phenol content with values of 924.3 and 935.0 mg of chlorogenic acid equivalents/100 g dried weight, respectively. Idealino pepper presented the highest capsaicin content (2932.1 μg/g dried weight). The antioxidant capacity was evaluated by using 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid test, 2,2-diphenyl-1-picrylhydrazyl test, and ferric reducing ability power assay. Both Pellegrino and Idealino samples exhibited a promising radical scavenging ability against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid radical with IC₅₀ values of 45.2 and 45.7 μg/mL, respectively. All the extracts were able to inhibit the growth of Staphylococcus aureus and Listeria monocytogenes investigated strains. The most active are Effix and Fantasia peppers with minimal inhibitory concentration between 12.5 and 25.0 mg/mL, respectively. Overall, these results support the use of these pepper species as dried extract in food preservation.     

Comparison of the compositional, microbiological, biochemical and volatile profile characteristics of three Italian PDO fermented sausages

Three Italian PDO fermented sausages, Varzi, Brianza and Piacentino, were compared for compositional, microbiological, biochemical and volatile profile characteristics. Mean values for the gross composition varied especially due to moisture, fat, total protein and nitrate concentration which reflected differences in the ingredients and some technological parameters. Cell numbers of the major microbial groups were almost similar among sausages. The major differences were found for Brochothrix thermosphacta, enterococci and moulds. Apart from their use as starters, Lactobacillus sakei and Lactobacillus curvatus were the dominant lactic acid bacteria and, as well as Staphylococcus xylosus, dominated the population of coagulase-negative staphylococci. Sausages differed for the hydrolysis of myofibrillar proteins and secondary proteolysis. Varzi, the sausage subjected to prolonged fermentation at 23–25 °C for 10 days before ripening, showed the highest degree of secondary proteolysis. Varzi and Brianza, the two fermented sausages manufactured by using microbial starters, showed the highest concentration and similar profiles of free amino acids. The peptidase activities contained in the aqueous extracts agreed with the above findings. A total of 52 volatile components, mainly alcohols, aldehydes and terpenes, were identified by solid-phase micro-extraction coupled with gas chromatography–mass spectrometry analysis. The volatile profiles of the three Italian PDO fermented sausages differed in part and, except for terpenes, the highest levels of the other chemical classes were found in Varzi and Brianza sausages. The composition of free fatty acids of the three Italian PDO sausages was rather similar. Monounsaturated fatty acids (MUFA) were found at the highest relative percentage followed by saturated (SFA) and polyunsaturated (PUFA) fatty acids. Oleic, palmitic, linoleic and stearic were the main free fatty acids found in all fermented sausages.     

Enterococcus populations in Pecorino Abruzzese cheese: biodiversity and safety aspects

The presence of enterococci in Pecorino Abruzzese cheese during ripening was evaluated. Counts were high, especially in fully ripened summer batches. Seventy strains were isolated and identified based on phenotypical and genotypical features as Enterococcus faecium (48.5%), Enterococcus faecalis (40%), and Enterococcus durans (11.5%), with the first species predominant in spring batches and the second predominant in summer batches. High biodiversity was revealed by random amplification of polymorphic DNA and a PCR assay, suggesting the presence of autochthonous strains. E. faecium isolates were the most resistant to the tested antibiotics, especially to erythromycin, chloramphenicol, and penicillin, but all strains were susceptible to vancomycin, as confirmed by the absence of vanA and vanB genes. The presence of some virulence determinants was investigated, revealing the diffusion of aggregation substance (asal) and gelatinase (gelE) genes in 37.5% of E. faecalis strains. However, none of the isolates produced gelatinase in vitro, suggesting the presence of silent genes. The virulence genes were absent in E. durans. Among E. faecium strains, only Lab 41/1 possessed gelE and asal, whose presence previously has been reported only in E. faecalis. Decarboxylating activity was revealed for phenylalanine (27% of the strains) and tyrosine (96%) but not histidine. The presence of a tyrosine decarboxylase-encoding gene was observed for all strains. A comparison of these results with those of previous studies of clinical and food isolates indicates that enterococci from Pecorino Abruzzese cheese have low pathogenic potential.     

Recycled water: potential health risks from volatile organic compounds and use of 1,4-dichlorobenzene as treatment performance indicator

Characterisation of the concentrations and potential health risks of chemicals in recycled water is important if this source of water is to be safely used to supplement drinking water sources. This research was conducted to: (i) determine the concentration of volatile organic compounds (VOCs) in secondary treated effluent (STE) and, post-reverse osmosis (RO) treatment and to; (ii) assess the health risk associated with VOCs for indirect potable reuse (IPR). Samples were examined pre and post-RO in one full-scale and one pilot plant in Perth, Western Australia. Risk quotients (RQ) were estimated by expressing the maximum and median concentration as a function of the health value. Of 61 VOCs analysed over a period of three years, twenty one (21) were detected in STE, with 1,4-dichlorobenzene (94%); tetrachloroethene (88%); carbon disulfide (81%) and; chloromethane (58%) most commonly detected. Median concentrations for these compounds in STE ranged from 0.81 μg/L for 1,4-dichlorobenzene to 0.02 μg/L for carbon disulphide. After RO, twenty six (26) VOCs were detected, of which 1,4-dichlorobenzene (89%); acrylonitrile (83%) chloromethane (63%) and carbon disulfide (40%) were the more frequently detected. RQ(max) were all below health values in the STE and after RO. Median removal efficiency for RO was variable, ranging from −77% (dichlorodifluoromethane) to 91.2% (tetrachloroethene). The results indicate that despite the detection of VOCs in STE and after RO, their human health impact in IPR is negligible due to the low concentrations detected. The results indicate that 1,4-dichlorobenzene is a potential treatment chemical indicator for assessment of VOCs in IPR using RO treatment.     

Lipolysis, proteolysis and sensory characteristics of a Spanish fermented dry-cured meat product (salchichón) with oregano essential oil used as surface mold inhibitor

The superficial antifungal activity of oregano essential oil (OEO) in Spanish fermented dry-cured sausages ("salchichón"), and its effects on lipolysis, proteolysis and sensory characteristics were evaluated. The surface application of OEO reduced mold contamination on the surface, without significantly affecting the drying process. To evaluate the intensity of lipolysis during the ripening process, the profile and content of free fatty acids were determined. The addition of OEO led to a higher amount of unsaturated fatty acids, but lipolysis was not greatly affected. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), which was used to qualitatively assess the proteolytic changes in the sarcoplasmic and myofibrillar proteins during the process, pointed to very similar patterns in all the sausages. OEO did not significantly affect the sensory properties, but increased hardness, resulting in a better texture. Therefore, a shorter ripening time may be necessary for sausages treated with OEO.     

Molecular identification and osmotolerant profile of wine yeasts that ferment a high sugar grape must

The objective of this study was to examine the Saccharomyces and non-Saccharomyces yeast populations involved in a spontaneous fermentation of a traditional high sugar must (Vino cotto) produced in central Italy. Molecular identification of a total of 78 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. In addition, the isolates were differentiated by RAPD-PCR. Only a restricted number of osmotolerant yeast species, i.e. Candida apicola, Candida zemplinina and Zygosaccharomyces bailii, were found throughout all the fermentation process, while Saccharomyces cerevisiae prevailed after 15 days of fermentation. A physiological characterization of isolates was performed in relation to the resistance to osmotic stress and ethanol concentration. The osmotolerant features of C. apicola, C. zemplinina and Z. bailii were confirmed, while S. cerevisiae strains showed three patterns of growth in response to different glucose concentrations (2%, 20%, 40% and 60% w/v). The ability of some C. apicola and C. zemplinina strains to grow at 14% v/v ethanol is noteworthy. The finding that some yeast biotypes with higher multiple stress tolerance can persist in the entire winemaking process suggests possible future candidates as starter for Vino cotto production.     

Application of Central Composite Design to evaluate the antilisterial activity of hydro-alcohol berry extract of Myrtus communis L.

The antimicrobial activity of the hydro-alcohol extract of Myrtus communis L. (ME) berries was investigated against six Listeria monocytogenes strains (2 type strains and 4 isolates). Sub-lethal ME concentrations reduced L. monocytogenes counts by at least 2 log cycles. A Central Composite Design was used to investigate the combined effects of sub-lethal concentrations of ME (0.039–0.195 mL/100 mL), NaCl (0–2.0 g/100 mL) and pH (5.0–7.0) on strains growth. ME affected growth parameters, generally extending lag phase length and reducing maximum growth, sometimes with interactive effects with pH. The highest ME concentrations (0.117–0.195 mL/100 mL) combined with the lowest pH values (5.0–6.0) strongly reduced or even inhibited strains growth.     

Flow cytometric assessment of the antimicrobial activity of essential oils against Listeria monocytogenes

Flow cytometry was applied to assess the antimicrobial activity of oregano, thyme and cinnamon essential oils against Listeria monocytogenes ATCC19114, using combined staining with propidium iodide (PI) for membrane damage evaluation and carboxyfluorescein diacetate (cFDA) for esterase activity detection. The antimicrobial activity of the essential oils was also tested at different NaCl concentrations.Significant differences were observed between plate count results and flow cytometric data, which suggested the presence of a sublethally stressed subpopulation, not able to form colonies on agar plates.Following treatments, flow cytometric assessment clearly discriminated three different subpopulations: viable, dead and injured cells. Cinnamon essential oil exerted a different impact on the cellular subpopulations, with a lower overall activity and a large percentage of cells having minimally damaged membranes. On the contrary, membrane disintegration seemed to be the primary inactivation mechanism of oregano and thyme essential oils.The antimicrobial activity of the essential oils increased with NaCl concentration increase, but higher NaCl concentrations were necessary following treatments with cinnamon essential oil.Our findings suggest differences in the mode of action of cinnamon essential oil against L. monocytogenes, in comparison with thyme and oregano essential oils.     

Effect of high pressure homogenization applied individually or in combination with other mild physical or chemical stresses on Bacillus cereus and Bacillus subtilis spore viability

High pressure homogenization (HPH) has been proposed as an effective alternative to high hydrostatic pressure in the continuous sanitization of fluid food systems. In this study, we evaluated the influence of HPH treatment, applied individually (one, two or three cycles) or in combination with other mild physical or chemical stresses (mild heat treatment H₂O₂ and low pH), on the capability of Bacillus cereus and Bacillus subtilis spore, suspended in sterilized double distilled water, to form colonies. Although plate count only slightly decreased in all the strains when one cycle of HPH at 150 MPa was applied alone, the spores released significant levels of dipicolinic acid (up to 28%) that could indicate a possible disruption of spore layers. Three consecutive cycles of HPH determined high reduction of colony count (about 5 log CFU/ml) and high DPA release (52%). Among the stress conditions applied, it was observed that only the thermal shock after one HPH cycle reduced the colony count of 2.3 log CFU/ml and induced a DPA release up to 57%.These results suggested HPH as a novel application for B. cereus and B. subtilis control in fluid foods.     

Microbiological characteristics of kumis, a traditional fermented Colombian milk, with particular emphasis on enterococci population

Kumis is a traditional fermented cow milk produced and consumed in South West Colombia. The main objective of this research was to studied the enterococcal population, present in 13 kumis samples traditionally manufactured, for their role as beneficial organisms or opportunistic pathogens. The molecular identification of 72 isolates evidenced that Enterococcus faecalis and E. faecium were the dominant species. The genes gelE, esp, asa1, cyl and hyl, all associated with virulence factors in enterococci, were detected in 30 isolates, while 42 were free of virulence determinants. Skim milk media were fermented by all the different isolates and further tested for proteolysis (free NH₃ groups), Angiotensin-I Converting Enzyme (ACE) inhibitory activity and biogenic amines production. Nine E. faecalis and two E. faecium strains produced fermented milk with ACE-inhibitory activity values ranging from 39.7% to 84.35% .The digestion of fermented milk samples by pepsin and pancreatin evidenced an increase in ACE inhibitory activity, with E. faecalis KE09 as the best producer (IC50 = 14.25 μg ml⁻¹). Moreover, the strains showed a very low tyrosine decarboxylase activity and did not produce histamine during 48 h fermentation in milk. This study underlines the that Colombian kumis is a good source of not virulent enterococci able to produce fermented milks with ACE-inhibitory activity.