Untitled

Funder

Organizational Unit

Publications

Long-term frozen storage and pasteurization effects on strawberry polyphenols content

Publication . Oliveira, Ana; Coelho, Marta; Alexandre, Elisabete M. C.; Almeida, Domingos P. F.; Pintado, Manuela

The profile of the strawberry polyphenols was analysed on fresh strawberry, immediately after freezing or after pasteurization and during frozen storage of strawberry at -20 A degrees C for 360 days. Freezing increased the extractability of (-)-epigallocatechin gallate (60 %), (-)-epicatechin (48 %) and ellagic acid (51 %) and decreased the pelargonidin-3-glucoside (18 %). Direct pasteurization of fresh strawberry increased the extractability for (-)-epigallocatechin gallate (73 %), (-)-epicatechin (45 %) and ellagic acid (143 %) and decreased for pelargonidin-3-glucoside (16 %). During storage at -20 A degrees C for 360 days the extractable levels of pelargonidin-3-rutinoside, (-)-epigallocatechin gallate, (+)-catechin, (-)-epicatechin and ellagic acid decreased by 17, 20, 37, 65 and 80 %, respectively, while those of pelargonidin-3-glucoside increased 13 %. Changes in polyphenols content, produced by pasteurization after 360 days frozen storage, were minimal. Polyphenols content decreased during storage of strawberry pieces at -20 A degrees C for 360 days, while the thermal treatment applied after freezing storage did not induce any significant change.

2015Journal article

Restricted access

Impact of storage on phytochemicals and milk proteins in peach yoghurt

Publication . Oliveira, Ana; Coelho, Marta; Alexandre, Elisabete M. C.; Pintado, Manuela

Yoghurt supplemented with peach is a dairy product consumed around the world with a shelf-life of ca. 30 days. During this period protein–polyphenol complexes can be formed and have a detrimental effect on the in vivo solubility of both phenolic and proteins. Yoghurt enriched with peach preparate were produced and stored up to 28 days at 2 °C. Total antioxidant activity decreased 24%, total carotenoids increased 66%, while total phenolics remained unchanged during the yoghurt shelf-life. Carotenoids presented significant differences between peach enriched yoghurt and peach preparate stored under the same conditions. After 28 days the zeaxantin + lutein, β-cryptoxanthin and β-carotene increased 133, 122, and 84% respectively, for peach preparate, while in peach yoghurt they increased 68, 40, and 15%, indicating interactions of carotenoids with matrix components mainly proteins and fat present in yoghurt. Polyphenols presented higher stability when added to yoghurt with slight variations in their content of ca. 10% for (+)-catechin and 12% for p-coumaric acid, and no variations were recorded in neochlorogenic and chlorogenic acids and in rutin. The α-lactalbumin content decreased 22% after 24 h of peach addition while β-lactoglobulin content did not change. Peach polyphenols were very stable during yoghurt shelf-life while carotenoids were the compounds that presented higher interactions with the matrix.

2017Journal article

Restricted access

Behaviour of cyanidin-3-glucoside, β-lactoglobulin and polysaccharides nanoparticles in bulk and oil-in-water interfaces

Publication . Oliveira, Ana; Pizones Ruiz-Henestrosa, Víctor M.; von Staszewski, Mariana; Pilosof, Ana M. R.; Pintado, Manuela

Particle size distributions as well the interfacial and rheological properties of the films at the oil/water interface were used to study the effect of the interacting system between β-lactoglobulin, cyanidin-3-glucoside and pectin or chitosan in buffer solutions. The particles obtained were smaller with cy-3-gluc-β–lg-pectin and had reduced polydispersity with cy-3-gluc-β–lg-chitosan. Based on time dependent surface pressure results, β–lg-pectin mixtures showed a slower increase at the beginning of the measurement, while β-lg-chitosan mixtures showed no differences with β–lg alone. Contrarily, dilatational properties increased for ternary chitosan mixtures, but they remained similar to the pure protein in ternary pectin mixtures. Cy-3-gluc interfacial properties were reduced by the presence of pectin and chitosan. The interactions between cy-3-gluc and the biopolymers that have been selected in the present work resulted in a lower content of free polyphenol, reduced antioxidant properties as well as free β–lg. The impact of this effect was more relevant when pectin was used.

2015Journal article

Restricted access

Incorporation of strawberries preparation in yoghurt: impact on phytochemicals and milk proteins

Publication . Oliveira, Ana; Alexandre, Elisabete M. C.; Coelho, Marta; Lopes, Cláudia; Almeida, Domingos P. F.; Pintado, Manuela E.

An immediate decrease in the total antioxidant activity (23%) and total phenolic content (14%) was observed after addition of strawberry preparations to yoghurt. The total anthocyanin content did not change immediately, but decreased 24% throughout the yoghurt shelf-life. The individual compounds, (+)-catechin (60%), (-)-epicatechin (60%), kaempferol (33%) and quercetin-3-rutinoside (29%) decreased after 24 h in the yoghurt made with the strawberry preparation. During the remaining period of storage these compounds increased by 47%, 6%, 4% and 18%, respectively. Pelargonidin-3-glucoside decreased 49% after 28 d. Immediately after the addition of the strawberry preparation to yoghurt, beta-lactoglobulin decreased to values lower than the limit of detection and alpha-lactalbumin by approximately 34%, and was reduced further slowly throughout yoghurt self-life. An immediate interaction between the carrageenan present in the strawberry preparation and beta-LG was observed. The variations of both polyphenols and protein in the presence of carrageenan and the potential interactions were discussed.

2015Journal article

Restricted access

Phytochemicals preservation in strawberry as affected by pH modulation

Publication . Oliveira, Ana; Gomes, Maria Helena; Alexandre, Elisabete M. C.; Poças, Fátima; Almeida, Domingos P. F.; Pintado, Manuela

Strawberries purees are incorporated in foods and subjected to pH modulation according to the expected final food matrix. The effect of pH on strawberry polyphenols stored at 4 and 23 degrees C for 90 days was evaluated. Total antioxidant activity and total phenolics content were only affected by time according to a first order model. The pH 4.5 induced higher decrease in (-)-epigallocatechin gallate (71% and 79%) and quercetin-3-glucoside (29% and 36%), for both storage temperatures. For pH 2.5 and 3.0, ellagic acid increased 84% for 4 degrees C. and 185% for 23 degrees C. Anthocyanins concentration changes along storage were well described by first order model. The pH value of 2.5 presented the lower kinetic constant rate where cyanidin-3-glucoside, pelargonidin-3-glucoside and pelargonidin-3-rutinoside had a k = 0.04, 0.05 and 0.03 day(-1). Lower storage temperature (4 degrees C) and lower pH (2.5) were the best condition for the preservation of polyphenols in pasteurized strawberry during a 90-day storage period.

2015Journal article

Restricted access