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Processing slime from snail (Helix aspersa maxima): a preliminary study on the effect on microbial load

Publication . Teixeira, Raquel; Barbosa, Joana; Albano, Helena; Maciel, Cláudia; Silva, Joana; Saraiva, Jorge A.; Castro, Sónia M.; Teixeira, Paula

Slime from earth snails (Helix aspersa maxima) is a sub-product often used in the cosmetic industry. Due to its origin, a decontamination process ought to be considered. After exposure to UV radiation, no significant (P > 0.05) reduction of the initial microbial load of slime was observed, while treated at 60 °C, a decrease of 4.0 log CFU∙mL-1 was obtained (when compared to non-treated slime). A similar reduction was attained for pressurized (500 MPa) slime. The sequential combination of temperature and pressure treatment had a similar effect (P > 0.05) on the microbial load when compared to 400 MPa (30 min), but the reduction was higher when compared to the less intense treatments (60 °C, 15 min; 400 MPa, 15 min). Overall, the results suggest that pressure ( 400 MPa) is a promising technology for processing snail slime, which can have positive effects on its microbial load, for further use in the cosmetic industry

2018Journal article

Open access

Antimicrobial activity of ethanolic extract of propolis in "Alheira", a fermented meat sausage

Publication . Casquete, Rocío; Castro, Sónia Marília; Jácome, Samuel; Teixeira, Paula

The objective of this study was to evaluate the efficacy of an ethanolic extract of propolis (EEP) in the control of Listeria innocua PHLS 2030c (as a surrogate for Listeria monocytogenes) during storage of Alheira at 4°C. Total phenolic content was evaluated to determine the minimal inhibitory concentration of EEP against the growth of L. innocua by the agar dilution method. Alheiras were manufactured by incorporating EEP (0.28 mg/mL) and pathogenic bacteria and storage during 62 days at 4°C. Growth of L. innocua was determined during storage. The behaviour of L. innocua in the food matrix was significantly affected (p < 0.01) by the addition of EEP. The ethanolic extract of propolis reduced the Listeria population to below the detection limit of the technique after 8 days of storage. These results suggest that incorporation of EEP in a food susceptible to Listeria contamination may be an interesting alternative to existing chemical preservatives and can extend the shelf life of these products.

2016Journal article

Open access

Enhancement of bacteriocin production and antimicrobial activity of pediococcus acidilactici HA-6111-2

Publication . Garcia, J. M.; Castro, S. M.; Casquete, R.; Silva, J.; Queirós, R.; Saraiva, J. A.; Teixeira, P.

The effect of sequential treatments of pressure (50-150 MPa, 10 degrees C, 5 min) and temperature (57 degrees C, 15 min) on the survival and bacteriocin production of Pediococcus acidilactici HA-6111-2 cells in the exponential growth phase was assessed. The growth curves were fi tted with the modifi ed Gompertz model, and the estimated maximum specifi c growth rate was considered to be pressure dependent. A delay in the maximum value of bacteriocin production was registered for more severe pressure conditions, but it was found more notorious for pressure followed by temperature treatments. At lower pressure intensity treatment, regardless of the application order, there was an enhancement of bacteriocin production per cell when compared to the control while maintaining the maximum production value. Bacteriocin production after the treatments can be described by an exponential model.

2017Journal article

Restricted access

High hydrostatic pressure effects on Listeria monocytogenes and L. innocua: evidence for variability in inactivation behaviour and in resistance to pediocin bacHA-6111-2

Publication . Bruschi, Carolina; Komora, Norton; Castro, Sónia Marília; Saraiva, Jorge; Ferreira, Vânia Borges; Teixeira, Paula

The effect of high hydrostatic pressure (HHP) on the survival of 14 strains of Listeria monocytogenes from food or clinical origins, selected to represent different pheno and genotypes, was evaluated. Stationary phase cells were submitted to 300, 400 and 500 MPa at 10 °C, for 5 min. A high variability in the resistance of L. monocytogenes to pressure was observed, and particularly two strains isolated from food were significantly more baroresistant than the rest. Strains of L. monocytogenes resistant to one or more antibiotics exhibited significantly higher levels of survival after the high pressure treatment at 400 MPa. No correlation was found between strains' origin or thermal tolerance and resistance to HHP. The suitability of two strains of L. innocua as surrogates of L. monocytogenes, was also investigated. These exhibited significantly higher sensitivities to HHP than observed for some L. monocytogenes. The antimicrobial effect of the antilisterial bacteriocin (bacHA-6111-2) increased after L. monocytogenes cells had been exposed to pressure. The data obtained underlines the importance of strain selection for studies aiming to evaluate HHP efficacy to ensure safety of HHP-treated foods.

2017Journal article

Restricted access

Effect of a HPP pretreatment on thermal inactivation kinetics of polyphenoloxidase obtained from three apple cultivars

Publication . Machado, Maria F.; Sousa, Alexandra; Castro, Sónia M.; Moreira, Sílvia A.; Saraiva, Jorge A.

Enzymatic browning due to the action of polyphenoloxidase (PPO) is highly undesirable and efficient methodologies to avoid/reduce it are of great interest for food industry. The effect of a pressure pretreatment (100 MPa, 15 min, room temperature) on the activity of PPO extracts obtained from three apple cultivars (Bravo de Esmolfe [BE], Reineta [RN], and Golden delicious [GD]), and subsequent thermal inactivation kinetics was evaluated, as a way to more efficiently achieve thermal inactivation of PPO. The effect of pH on PPO activity was also assessed to define the value at which carry out the thermal inactivation of PPO. The enzymatic activity decreased in the order BE, RN, and GD. Two log-linear ranges ([62.5-72.5]degrees C and [72.5-80.0]degrees C) of D-value with temperature were found. The pressure pretreatment caused enhanced stability within the range of 62.5-67.5 degrees C, caused no changes at 70.0-72.5 degrees C, and decreased the stability at 75.0-80.0 degrees C (e.g., at 75 degrees C the D-values for BE, GD, and RN ranged, respectively, from 25.6/27.3, 14.5/18.6, and 8.8/10.4, after/before the pressure pretreatment) and increased thermal sensitivity (decreased the z-value), particularly in the lower temperature range studied (up to 72.5 degrees C). Practical applicationsKnowledge of PPO activity level and its thermal resistance for different cultivars is of interest to develop efficient and optimized enzymatic browning control by thermal treatments. Sequential combination of low intensity pressure treatments followed by thermal treatments can be an interesting approach to enhance enzyme inactivation. In this work was found that after a low intensity pressure pretreatment (100 MPa, 15 min), apple PPO temperature stability could be reduced, since a lower stability (lower D-values) and increased sensitivity toward temperature (lower z-value) was systematically found for PPO thermally inactivated at T>72.5 degrees C. These findings are of interest for a more efficient PPO inactivation for enhanced browning control.

2017Journal article

Restricted access