Marta Henriques

Growth aspects of the marine microalga Nannochloropsis gaditana

Nannochloropsis is well appreciated in aquaculture due to its nutritional value and the ability to produce valuable chemical compounds, such as pigments (zeaxanthin, astaxanthin...) and polyunsaturated fatty acids (EPA). Commercial exploitation needs high cell densities but the low growth rate and the small size of cells are practical difficulties. To increase biomass concentration the positive effect of several factors was evident: (i) pH approximately 8 control (with dilute Tris-HCl buffer); (ii) the continuous illumination (no evidence of photo-inhibition was observed); (iii) a quite large temperature range (25+/-5 degrees C); (iv) the presence of organic carbon source (with the danger of contamination); (v) the presence of urea as an additional nitrogen source (10 mM); (vi) a small air flow rate with large bubbles can be more efficient for CO(2) mass transfer (associated to reduced shearing).

Effects of Liquid Whey Protein Concentrate on Functional and Sensorial Properties of Set Yogurts and Fresh Cheese

The production and incorporation of liquid whey protein concentrates (LWPCs) in fresh cheese and set yogurt is proposed as a solution for immediate reutilization of whey produced by small- and medium-scale dairy plants avoiding expensive processing steps (e.g., evaporation and drying) for the recovery of this by-product. Accordingly, the incorporation of LWPCs in such products was performed in order to compare the functional and sensorial properties of modified products with the conventional ones. The use of LWPC in fresh cheese increased water-holding capacity as well as product stability during storage. Fresh cheese hardness, chewiness, and gumminess decreased during storage in a more pronounced way in products with LWPC. The fat content influences significantly all the physicochemical properties tested in set yogurts. Incorporating LWPC in set yogurts does not produce appreciable differences in the visual properties when considering products with medium-fat content, but these differences become significant for full-fat yogurts. Adhesiveness and springiness were not significantly affected with storage time or by the amount of LWPC incorporated for medium-fat yogurts. Higher values of hardness and gumminess were obtained for full-fat yogurts, but these parameters decreased with LWPC incorporation. Syneresis was reduced using LWPC but increased with storage time. During storage, viscosity differences between LWPC incorporated yogurts and the conventional ones were only maintained in the case of creamy yogurts. The sensory panel detected differences between conventional and modified products in the case of fresh cheeses but no significative differences were detected between yogurts. LWPCs can be a good alternative to conventional dry products used in fresh cheese and set yogurt manufacture since their utilization reduces milk consumption and allows for the increase in total solids content. Additionally, their incorporation in milk originates end products with attractive physicochemical and sensorial characteristics at lower production costs.

Whey Protein Edible Coatings: Recent Developments and Applications

Increasing concerns about reducing the use of limited resources and substituting them with renewable alternatives stimulated the production of edible and biodegradable films and coatings. These materials have already shown good performance in preventing mass transfer from foods and increasing their quality and shelf life. Whilst many biopolymers such as wheat, gluten, soy protein, starch, cellulose and casein have been studied as edible films and coatings, this chapter reviews the existing literature on whey protein-based films and coatings and states their recent developments and applications. The main topics are: (1) functions of edible whey protein films and coatings applied to food systems; (2) their composition; (3) the identification of some available and emerging methods for its production; (4) a discussion of the existing and potential applications for whey protein films and coatings as active food systems; and (5) a case study of bioactive whey protein coatings applied to ripened cheese.

Fermented dairy products based on ovine cheese whey

This work presents an alternative solution for ovine whey components recovery in medium/small cheese plants that predominate in the rural areas of Southern European countries, which are specialized in the production of protected designation of origin (PDO) cheeses. These plants lack the capacity to concentrate and dry whey, and although a significant amount of this by-product is used in the manufacture of whey cheeses, in several cases it is used as animal feed or simply discarded. As an alternative to these practices, we propose the production of liquid whey protein concentrates (LWPC) by means of ultrafiltration (UF) followed by thermal denaturation and homogenization and their utilization in the production of fermented products based on kefir grains and/or commercial probiotic bacteria. Two types of fermented products were prepared: one in a liquid form (low protein and fat contents) and other in a gel form (high protein and fat contents). The microbiological, physicochemical (gross composition, pH, titratable acidity) and rheological properties of such products were assessed and compared during fermentation and at the 7th, 14th and 21st days of refrigerated storage. The fermented products presented adequate amounts of lactococci, lactobacilli (>7 Log10 CFUmL-1) and yeasts (>6 Log10 CFUmL-1). The rheological properties of liquid products were stable during the 21 days of refrigerated storage. However, gel type products showed variations in viscosity after 14 days, in the cases in which kefir grains were present. Although further work is needed in order to optimize the formulations regarding to the improvement of their sensory properties, it was concluded that this approach allows for the production of innovative fermented dairy products.