Open Access
Physical, chemical and microbiological changes in liquid micellar casein concentrates induced by high-pressure treatments
(Elseiver, 2022) García Amezketa, Arantza; Iturmendi Vizcay, Nerea; Galarza Iriarte, Uxue; Maté Caballero, Juan Ignacio; Fernández García, Teresa; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
Microfiltration and diafiltration were conducted to obtain 3 distinct levels of liquid micellar casein concentrates from raw skim milk: 8, 10 and 11.5 g casein/100 g. All the concentrates were subjected to 300, 450 and 600 MPa for 5 min. The physicochemical and microbiological changes in the matrix were studied and compared with their untreated counterparts on the day of production and after storing the samples for 7 d at 10 °C. Slight changes in pH were correlated with pressurization; the higher the pressure the greater the decrease in pH. For the least concentrated sample, changes were more noticeable. Furthermore, changes in particle size mainly occurred as a consequence of pressurization but also depended on casein concentration: aggregation and disruption phenomena were observed in the most concentrated samples. In terms of microbial quality, 600 MPa was the only treatment capable of achieving effective microbial control.
Open Access
Morphometry and textural surface properties of heat induced whey protein microparticles
(Elsevier, 2025-09-01) Angós Iturgaiz, Ignacio; Vele, Lenin; Espinosa Rábanos, Isabel; Iturmendi Vizcay, Nerea; Fernández García, Teresa; Maté Caballero, Juan Ignacio; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
The present work focuses on the study of four key factors controlling the process of whey protein microparticulation: protein suspension concentration (%WPI 2.5 % vs. 5.0 %); medium acidity (pH 4.5 vs. 5.5); denaturation temperature (80◦C vs. 90◦C); and particle size reduction method (180 bar x 1, 2 or 3 cycle(s); 1800 bar x 1 cycle). The effects of the microparticulation process were studied by analysing the degree of protein aggregation, morphometry, and surface textural characteristics of the microparticles. The results obtained indicate that the most favourable treatments to achieve a higher proportion of particles within the optimal range required by the food industry (1–10 μm) can be obtained by gentle protein denaturation (80◦C) using a medium with a pH lower than the isoelectric point of β-lactoglobulin and moderate concentrations of whey protein (2.5–5.0 %). Under these premises, it is necessary to use a high intensity particle size reduction method (1800 bar) to achieve the average diameter and the adequate homogeneity in a consistent fashion.
Open Access
Combined effect of antimicrobial edible coatings with reduction of initial microbial load on the shelf-life of fresh hake (Merluccius merluccius) medallions
(Wiley, 2019) Otero Tuárez, Víctor Oswaldo; Carrión Granda, Ximena; Fernández Pan, Idoya; Fernández García, Teresa; Maté Caballero, Juan Ignacio; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
Two distinct strategies were combined to preserve fresh fish (Merluccius merluccius) under refrigeration at 4 °C for 12 days: (i) the application of an antimicrobial edible coating enriched with oregano essential oil (OEO) or carvacrol (CV) and (ii) the reduction of initial microbial load by good handling practise and the use of sodium hypochlorite (NaOCl). The action of antimicrobial coatings alone retarded the growth of Enterobacteriaceae, lactic acid bacteria (LAB) and H2S producing bacteria on fish samples. The reduction of initial microbial load by itself only affected the evolution of LAB, but not the rest of the bacterial groups. When using both techniques combined, edible antimicrobial coatings were significantly more effective with additional and significant delays in the growth of mesophilic, psychrotrophic and Pseudomonas bacteria. Thus, the use of both strategies combined resulted in a reduction of the counts of all bacterial groups after 12 days of storage which ranged from 1.5 log and 8 log, in Pseudomonas and H2S producing bacteria, respectively. Moreover, no significant differences were observed when comparing the microbiological evolution of samples treated with OEO compared to those only treated with CV.
Open Access
Evolution of microbial and protein qualities of fractions of milk protein processed by microfiltration
(Elsevier, 2022) Galarza Iriarte, Uxue; Iturmendi Vizcay, Nerea; García Amezketa, Arantza; Fernández García, Teresa; Maté Caballero, Juan Ignacio; Agronomia, Bioteknologia eta Elikadura; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Agronomía, Biotecnología y Alimentación; Gobierno de Navarra / Nafarroako Gobernua
In dairy industry there has always been great concern about the microbial and protein quality of liquid milk protein fractions obtained by microfiltration (MF). The objectives of research were to study the impact of MF on the evolution of protein and microbial quality of microfiltered milk (MFM), liquid micellar casein concentrates (LMCC) and serum permeates (SP) during storage at 4 °C. This study was carried out with three different batches of milk using diafiltration. Samples were characterized by physicochemical properties; evolution of microbial load and protein (RP-HPLC). Ceramic MF (pore size 1.4 μm) did not change the protein profile, but reduced microbial load by up to 2 log CFU/mL. Polymeric MF (pore size 0.1 μm) was not a sterilizing process since all samples from the permeate presented bacterial growth after 6 days. Protein degradation was observed after 13 days at 4 °C in all studied products. Caseins (CN) were much more affected than whey proteins. β-CN A2 content was reduced by 25–50%, αs1-CN by 30% and β-CN A1 by 10–30%.; κ-CN was the most stable casein. The contents of the whey proteins remained unaltered for 21 days. Protein degradation was likely due to the action of endogenous and bacterial enzymes.
Open Access
Combined effect of nisin addition and high pressure processing on the stability of liquid micellar casein concentrates
(Elsevier Science, 2022) García Amezketa, Arantza; Iturmendi Vizcay, Nerea; Maté Caballero, Juan Ignacio; Fernández García, Teresa; Agronomia, Bioteknologia eta Elikadura; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Agronomía, Biotecnología y Alimentación; Gobierno de Navarra / Nafarroako Gobernua
The combined effect of high pressure (HP) processing and the addition of nisin on the microbial quality of liquid micellar casein concentrates (LMCCs) at two different concentrations (7 and 10%) were investigated. Two pressure levels were applied (300 and 450 MPa over 5 min) with three different nisin levels (0, 250, and 500 IU mL 1). Microbial and physicochemical quality were studied at day 0 and after 7 days at 10 C. Results indicated that low-intensity HP treatment (300 MPa) alone or in combination with nisin was not effective enough to limit microbial growth after storage (10 C, 7 days). However, 450 MPa HP treatment combined with nisin addition showed efficiency in bacterial control, without affecting physicochemical properties (acidity, pH, and colour). It has been proved that nisin has the potential to enhance the bacteriological effectiveness of HP processing and thus extend the self-life of LMCCs without altering their physicochemical properties.
Open Access
Influence of high hydrostatic pressure treatments on the physicochemical, microbiological and rheological properties of reconstituted micellar casein concentrates
(Elsevier, 2020) Iturmendi Vizcay, Nerea; García Amezketa, Arantza; Galarza Iriarte, Uxue; Barba González-Albo, Carmen; Fernández García, Teresa; Maté Caballero, Juan Ignacio; Agronomia, Bioteknologia eta Elikadura; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Agronomía, Biotecnología y Alimentación