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- Effect of different conditions of growth and storage on the cell counts of two lactic acid bacteria after spray drying in orange juicePublication . Barbosa, Joana; Borges, Sandra; Teixeira, PaulaConsumers increasingly require innovative food products with health benefits. Thus, a dried orange juice incorporating probiotics could be a novel challenge. In this context, we investigated whether different sugars added to the culture media used for growth of two lactic acid bacteria contributed to their protection during spray drying in orange juice and subsequent storage under different conditions of temperature, light exposure and water activity. Cell viability during passage through simulated gastro-intestinal conditions was also investigated. Cells grown in culture medium containing fructose resulted in the worst survival rates during storage. High survival was observed for cells grown in the presence of lactose, followed by glucose. The survival of dried bacteria was enhanced at 4 C, water activity of 0.03 and absence of daylight. For cells grown in standard culture medium and after 12 months of storage at 4 C in orange juice powder (about 109 cfu/mL), there was a reduction of approximately 2 log-units for both lactic acid bacteria after gastro-intestinal tract passage simulation. Using the conditions of growth and storage investigated, it is possible to improve the survival rate of lactic acid bacteria and produce an orange juice powder with probiotic characteristics with shelf life of at least 12 months.
- Development of a functional orange juice powder by spray dryingPublication . Barbosa, Joana Inês Bastos; Teixeira, Paula Cristina MaiaThe concept of functional food products has acquired a huge dimension with the enormous number of people concerned about consuming foods with health benefits. An innovative non-dairy functional food would be very attractive, not only to these consumers but also to specific niches in the market (e.g. lactose intolerants and vegetarians). The aim of this work was to develop a powdered functional orange juice. For this, cultures with probiotic characteristics were used and the necessary conditions to obtain the dried product by spray drying were defined. Two cultures were selected, a commercial probiotic, Lactobacillus plantarum 299v and an isolate from a food matrix, Pediococcus acidilactici HA-6111-2. Safety and the presence of some functional characteristics of P. acidilactici were investigated and compared with those of the commercial probiotic. None of the bacteria produced any of the virulence factors investigated; they did not exhibit significant resistance to antibiotics and reductions lower than one logarithmic cycle were observed after exposure to simulated gastro-intestinal tract conditions. It was also verified that both bacteria survived during the spray drying process and subsequent storage for 60 days. Powdered orange juice was initially obtained in a Büchi Mini Spray Dryer at constant feed temperature (ºC), flow rates of feed (mL/min), drying air (%) and compressed air (L/h) and varying inlet and outlet air temperatures (ºC) as well as the ratio of total soluble solids (orange juice): drying aid (10DE maltodextrin or gum Arabic). At selected inlet and outlet air temperatures of 120 ºC and 65 ºC, respectively, and ratio of soluble solids: drying aid of 0.5: 2, high drying yields and powders with low water activities (aw) were obtained. No cell inactivation was observed for each culture after incorporated into orange juice and spray dried. Their survival during storage at 4 ºC was higher than at room temperature under uncontrolled aw. Pediococcus acidilactici was more resistant than L. plantarum, especially during storage at 4 ºC, with logarithmic reductions lower than 1 log-unit during a period of at least seven months. To enhance survival of spray dried bacteria during storage, different pre-spray drying conditions were tested: i) different sugars were added to the culture media used (cell growth in the presence of lactose, followed by glucose resulted in the highest survival) and ii) cells were exposed to different sub-lethal stresses (only survival of L. plantarum cells during storage at room temperature was increased). For both cases, powders obtained were stored under different conditions of temperature, light exposure and aw. Generally, survival was enhanced at 4 °C, aw of 0.03 and absence of light. Cell viability during passage through simulated gastro-intestinal tract conditions was also investigated at the end of the storage at 4 ºC; the viability of both cultures was not enhanced by prior exposure to sub-lethal stresses. Survival of cultures in orange fruit powders obtained by spray-, freeze- and convective hot air drying was investigated during drying and subsequent storage. Cell inactivation was only observed during convective hot air drying (about 2 logarithmic cycle reduction). Minimal reductions were observed for P. acidilactici for most conditions of storage while for L. plantarum only during storage at 4 ºC. Taking into account the initial number of cells obtained after each drying process, the techniques which allowed survival of an increased number of cells after storage, were spray- and freeze drying. Better dissolution, color and vitamin C retention were also obtained when these techniques were used. Despite the scale-up and validation at industrial scale being still necessary, spray drying at pilot scale allowed producing a new functional orange juice powder with probiotic characteristics. The bacteria used demonstrated to be good candidates for the development of this product.
- Food safety in local farming of fruits and vegetablesPublication . Macieira, Ariana; Barbosa, Joana; Teixeira, PaulaThe world’s population will be around 9 billion people by 2050. Humans need to feed in order to survive and thus the high demographic growth may impact the sustainability of our food systems. Sustainable food production practices such as local farming have been explored. Consumption of vegetables and fruits has been increasing due to their health benefits, but this increase is also related to a significant number of foodborne outbreaks. Foodborne outbreaks pose a threat to public health and the economy on a local and national scale. Food safety begins on the farm and proceeds over the supply chain. Thus, to provide safe products, food producers must follow specific procedures to avoid food hazards along the supply chain. This work aimed to present the importance of food safety in vegetables and fruits in local farming, as this form of production and consumption has increased in several countries of the northern hemisphere and as these are considered a form of providing more sustainable food products.
- Evaluation of antibiotic resistance patterns of food and clinical Listeria monocytogenes isolates in PortugalPublication . Barbosa, Joana; Magalhães, Rui; Santos, Isabel; Ferreira, Vânia; Brandão, Teresa R. S.; Silva, Joana; Almeida, Gonçalo; Teixeira, PaulaThe aim of this study was to characterize a broad collection of isolates of Listeria monocytogenes, of different serotypes, recovered in Portugal between 2003 and 2007 from foods (n = 353) and from clinical cases of human listeriosis (n = 95), in terms of antimicrobial susceptibility. All the isolates were susceptible to ampicillin, the preferred agent to treat listeriosis. Resistances to nitrofurantoin (n = 99), to ciprofloxacin (n = 18), to erythromycin (n = 10), to tetracycline (n = 2), to gentamicin (n = 1) and to rifampicin (n = 1) were observed. One hundred (28.3%) and 20 (21.0%) food and clinical isolates, respectively, were resistant to at least one antibiotic. Eight isolates (1.8%) were resistant to two or more antimicrobials of different classes, and all were collected from foods. Serogroup IVb included the highest percentage of isolates resistant to erythromycin. The highest percentages of isolates resistant to nitrofurantoin were of serogroup IVb and IIc. It was demonstrated that the incidence of antibiotic-resistant isolates of L. monocytogenes, during the period 2003 to 2007, was low in Portugal but still higher than that observed in other countries. Given the increasing population at greater risk of listeriosis, namely, the elderly, the high mortality rate of the infection and the detection of resistant isolates, monitoring for antibiotic resistance in strains of L. monocytogenes on a large scale, and assessing the risk of infection by these strains, is highly recommended.
- Characterisation of alheiras, traditional sausages produced in the North of Portugal, with respect to their microbiological safetyPublication . Ferreira, Vânia; Barbosa, Joana; Silva, Joana; Felício, Maria Teresa; Mena, Cristina; Hogg, Tim; Gibbs, Paul; Teixeira, PaulaThe objective of this study was the characterisation of alheiras, traditional Portuguese sausages, with respect to their microbiological safety. Thirty-eight lots from 17 producers were analysed. The microbiological status of the analysed product can be considered of concern in terms of food safety. Although Campylobacter spp. and Escherichia coli O157 were not detected in any sample,and Clostridium perfringens when present was not at levels of concern with reference to public health, Salmonella spp. were detected in 2 lots of industrially produced alheiras, and more than 60% of the lots analysed were contaminated with Listeria monocytogenes in concentrations higher than 100 cfu/g.
- Characterization of a bacteriocin of pediococcus pentosaceus SB83 and its potential for vaginal applicationPublication . Borges, Sandra; Barbosa, Joana; Silva, Joana; Teixeira, PaulaListeria monocytogenes, the responsible agent for listeriosis, is one of several microorganisms which can be transmitted from mother to fetus/neonate by vertical transmission. The aim of this study was to characterize a bacteriocin produced by Pediococcus pentosaceus SB83 for vaginal application, to prevent colonization of pregnant women with L. monocytogenes. Bacteriocin SB83 showed inhibitory activity against L. monocytogenes (serotypes 1/2a 1/2b and 4b) but did not inhibit vaginal lactic acid bacteria. Additionally, bacteriocin SB83 inhibited the growth of Enterococcus faecalis, Enterococcus faecium and Bacillus subtilis. Bacteriocin SB83 was produced at maximum levels between 24 h and 36 h of growth (6400 AU/mL against serotype 1/2b and 4b, 3200 AU/mL against serotype 1/2a). Significant reduction in antimicrobial activity was observed after treatment of cell-free supernatants with proteinase K, pepsin, papain and trypsin. Bacteriocin SB83 was resistant to treatments with Tween 80, Tween 20, Triton X-100, SDS and EDTA. This bacteriocin was stable at pH values between 4 and 6.5; a decrease in activity was observed at pH 2 and above 8. A decrease in antibacterial activity was recorded at 100 °C and 121 °C. In the range 4 °C to 80 °C, antimicrobial activity was not affected. The activity of bacteriocin did not change in simulated vaginal fluid (pH 4.2, 5.5 and 6.5). The molecular size of bacteriocin SB83 was between 3.5 and 6.5 kDa.In conclusion, the bacteriocin produced by P. pentosaceus SB83 has been proved to be resistant to several conditions, including conditions in the vaginal tract (pH and components of vaginal fluid).
- Development of probiotic fruit juice powders by spray-drying: a reviewPublication . Barbosa, Joana; Teixeira, PaulaThe use of spray-drying for the production of powdered fruit juices has been a common practice in recent years since it is a simple, economic, and advantageous technique. The current knowledge on the different spray-drying parameters, allowing the best conditions to obtain high-quality powders, is presented in this review. The incorporation of probiotic cultures into fruit juices can enhance the functional characteristics of fruit juices. The selection of these probiotics and their benefits to consumers' health are briefly discussed. As maintaining the viability of probiotics is extremely important in the development of a probiotic functional product, the factors that influence and improve survival, in all pre- and post-spray-drying steps, are also detailed. Finally, a few studies on probiotic fruit juices obtained by spray-drying are cited. Industries should bet on their development and commercialization, since despite being challenging to develop, these are very innovative and attractive products meeting modern consumer demands.
- Evaluation of a bacteriocinogenic Lactobacillus plantarum strain on the microbiological characteristics of “Alheira de Vitela”Publication . Macieira, Ariana; Albano, Helena; Pinto, Miguel; Linheiro, Raquel; Barbosa, Joana; Teixeira, PaulaLactic Acid Bacteria (LAB) and their bacteriocins can be successfully used as natural preservatives in meat products. This work aimed to investigate the effect of fresh and lyophilized starter cultures of an autochthonous bacteriocinogenic LAB strain (Lactobacillus plantarum ST153Ch: bac + culture) on the microbiological characteristics of “Alheira”, a traditional Portuguese smoked product. “Alheira” with the addition of fresh or lyophilized culture (ca. 108 cfu/g) and “Alheira” control (no bacteriocinogenic culture added) were produced by an industrial meat company. The antilisterial activity of this culture in this food matrix was investigated, with some samples being inoculated with Listeria monocytogenes (ca. 105 cfu/g). Detection of L. monocytogenes, Salmonella spp., sulphite reducing clostridia, Yersinia enterocolitica and enumeration of L. monocytogenes, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Enterobacteriaceae, lactic acid bacteria, yeasts and moulds were performed immediately after production and at 3, 7, 15, 21, 28, 60 and 90 days of storage at 4 ℃, according to ISO methodologies. Also, a 16S rRNA Gene Analysis was performed of the microbial communities of “Alheira” with and without the lyophilized bacteriocinogenic culture. Pathogenic and indicator organisms were not detected or were below acceptable levels in all samples. LAB counts increased during storage and reached similar values after 15 days (ca. 1010 cfu/g) in all samples. There was a clear trend for a higher reduction of L. monocytogenes in the presence of the bioprotective culture, more pronounced during the initial 15 days of storage. From the analysis of the microbial communities of samples of “Alheiras” at different stages of fermentation, Leuconostocaceae and Lactobacillaceae predominated in all the samples and Lactobacillus was the genus more prevalent in “Alheiras” after 60 days of storage with the addition of bacteriocinogenic culture.
- Listeria monocytogenes: biofilm formation abilityPublication . Barbosa, J.; Carvalheira, A.; Gibbs, P.; Teixeira, P.
- Clinical isolates of L. monocytogenes: serotyping, biotyping and susceptibility to antibioticsPublication . Almeida, G.; Ferreira, V.; Magalhães, R.; Barbosa, J.; Silva, J.; Teixeira, P.; Hogg, T.