Browsing by Author "Nova, P."
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- Effect of the application of bioactive extracts on the storage time of smoked horse mackerel (Trachurus trachurus) with reduced saltPublication . Barros, D.; Nova, P.; Cunha, S.; Barbosa, C.; Pintado, M.; Gomes, A.; Vaz-Velho, M.Smoking of food is one of the oldest preservation methods and quite popular among fish and meat preservation strategies. The process combines salting, drying, heating and smoking steps. Salting and smoking, besides their preserving effects, are important to add flavour so appreciated by traditional foods consumers1-3. However, reducing salt intake is an important public health issue. Thus, both food industry and food services are interested in reducing the salt content of products4. Moreover, today's consumer is also looking for more natural foods with high nutritional value and functionality 5,6. Special attention has been given to the addition of bioactive compounds mainly with antioxidant and antimicrobial activities7-9. The general objective of the present study was the valorisation of low commercial value and abundant fish species such as horse mackerel (Trachurus trachurus) by developing smoked products with reduced salt content and fortified with natural bioactive compounds extracted from seafood and forest by-products. The fish, obtained in the local auction market, was smoked in a semi-industrial smoking oven for 4 h at 70 °C with a final thermal shock step of 1 h at 90 °C. Smoked fillets were divided into four groups and sprayed with one of four bioactive extract solution (100 mg/ml): two different solutions of mussel extract with peptides <3kDa, one solution of microalgae extract, Tetraselmis sp. with peptides <3KDa and a pine bark extract (Pinus pinaster Aiton subsp. atlantica) solution. A control sample without any spraying completed the set of five samples. Smoked fillets were vacuum-packed and stored at 4-6 °C, over 30 d. Quality changes, over the 30 days of storage, were studied by monitoring microbiological and physicochemical properties at weekly intervals. For microbial enumeration a pack was opened weekly, and 30 g of smoked fish was taken aseptically, from different sites, and homogenised for 90 s in a stomacher and subsequently decimally diluted. Total viable counts were performed on pour plates according to EN ISO 4833-1:2013; psycrotrophic microorganisms according to ISO 17410:2001; Enterobacteriaceae counts according to ISO 21528-2:2017 and yeasts and molds according to NP 3277-1:1987. Detection of Salmonella and Listeria monocytogenes was done according to ISO 6579-1: 2017 and ISO 11290-1:2017, respectively. Physicochemical properties analysed included: salt (NaCl) content, aw, moisture, pH, peroxide value index (PV) and thiobarbituric acid index (TBA), antioxidant activity (DPPH and ABTS methods), colour and firmness. Sensory evaluation by quantitative descriptive analysis (11 attributes) was performed by four trained panellists. Average total viable cell numbers were similar among all samples (including control) except for mussel extract MuE (CPC) that maintained levels above 8 log CFU, form 2 wk of storage onwards; the remaining samples demonstrated a steady increase in total viable cell numbers (30 ºC) only from 21 d onwards and reached final numbers between 6-7 log CFU. Enterobacteriaceae were reported constantly between 1-2 log CFU, molds were undetectable and yeasts reached higher viable numbers (3 log CFU) in smoked fillets with mussel extracts. Salmonella and Listeria were not detected throughout storage. In terms of antioxidant activity samples were quite stable over time. Concerning degradation indicators, such as TBA and PV, no tendency was noticeable. TBA index after 7 d of storage was low and stable and PV was unstable. Nevertheless, panellists found some off-flavours during their evaluation especially in the samples with mussel extract and microalgae extract that was more intense after 15 d of storage (Figure 1). The pine bark-treated samples presented more similarity with the control samples throughout storage. Texture and firmness were generally stable over time and with small differences between treatments, control samples showing higher values. Principle component analysis applied to physicochemical data (Figure 2) showed that antioxidant activity and pH, moisture and water activity discriminate samples over time (PC1) and, sample treatment with mussel extract MuE(ESB) as well. In this output, samples with higher values are projected towards the left side and this was also clear in pine bark (PBE) treated samples. Samples with mussel extract (MuE(ESB)) are quite stable (PC1) except for those with 7 d of storage. Overall, these results indicate the potential of these treatments to extend shelf-life of fish products and contribute to reintroduce sea and forest by-products into the food chain along adding value to abundant and undervalued fish products.
- Microalgae hydrolysates as functional ingredientsPublication . Cunha, S. A.; Nova, P.; Silva, J. L. da; Pintado, M. E.Microalgae have been used in food and cosmetic industries due to their richness in compounds with high biological value, such as proteins, essential amino acids, vitamins and minerals [1]. Several microalgae contain high protein content, similar to other common protein sources such as meat and soybean [1], making them a promising source of bioactive peptides. Bioactive peptides are inert inside proteins but can show several interesting properties when isolated [2]. Antioxidant, antihypertensive, antidiabetic, anticancer, anti-inflammatory and anti-aging are some properties that can be found described in bioactive peptides. Bioactive peptides may be more easily absorbed by the gastrointestinal tract than the intact protein, which allied with their potential bioactivities make them interesting for the development of functional foods, with health benefits for the consumer. Hypertension is one of the main causes of cardiovascular diseases, which can lead to heart attack or stroke. Angiotensin-converting enzyme (ACE) is involved in blood pressure regulation, thus inhibiting it can help to control high blood pressure. Thus, this research aimed to produce water soluble hydrolysates rich in proteins and bioactive peptides, with antioxidant and anti-hypertensive potential, from the five microalgae species Chlorella vulgaris, Nannochloropsis oceanica, Tetraselmis sp., Scenedesmus obliquus and Phaeodactylum tricornutum. The five microalgae species were submitted to an enzymatic hydrolysis (one of the most described methods for producing bioactive peptides) with a cellulase and a subtilisin protease, using previously optimized methods. Prior to the enzymatic hydrolysis, C. vulgaris was submitted to an acid hydrolysis, using a weak and food-grade acid. The anti-hypertensive potential was evaluated by the hydrolysate’s ability of inhibiting ACE. Previous studies [3] showed that C. vulgaris and S. obliquus hydrolysates stood out with the higher antioxidant potential. All the hydrolysates demonstrated anti-hypertensive potential by showing an IC50 lower than 500 μg protein/mL for ACE inhibition (Table 1). Thus, production of peptide hydrolysates from microalgae may represent an interesting approach for the development of sustainable, natural functional ingredients to be used to prevent hypertension on the consumers by incorporating it in food matrices.In conclusion, the enzymatic hydrolysis of microalgae allowed to produce hydrolysates with antioxidant and anti-hypertensive potential. Further studies should be done to confirm the anti-hypertensive ability after the gastrointestinal digestion of the hydrolysates. If the bioactivity is maintained, these hydrolysates may be incorporated in food matrices as functional ingredients, contributing to the development of functional foods with antioxidant and anti-hypertensive benefits for the consumers.