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Alternative sweeteners, such as steviol glucosides from the plant Stevia rebaudiana Bertoni, are becoming increasingly popular for the design of next-generation foodstuffs. However, the bitter aftertaste of native steviol glucosides is one of the main reasons behind consumer reluctance towards stevia-containing products. Biocatalysis could be a sustainable solution to this problem, through addition of glucosyl moieties to the molecule. Glycoside hydrolases are enzymes performing transglycosylation reactions, and they can be exploited for such modifications. In the present work, the commercial β-glucanase Finizym 250L® was employed for the transglycosylation of stevioside. After optimization of several reaction parameters, the maximal reaction yield obtained was 19%, with barley β-glucan as the glycosyl donor. With the aim to develop a sustainable process, β-glucan extracts from different fungal sources were prepared. Pulsed Electric Field pretreatment of mycelial biomass resulted in extracts with higher β-glucan content. The extracts were tested as alternative glucosyl donors, reaching up to 15.5% conversion yield, from Pleurotus-extracted β-glucan. Overall, in the present work a novel enzymatic process for the modification of stevioside is proposed, with concomitant valorization of β-glucans extracted from fungal biomass, potentially generated as a byproduct from other applications, in concert with the principles of circular economy. [ABSTRACT FROM AUTHOR]

The research targeted on the production of an innovative shelf-stable cheese of high quality, through the combinatory effect of osmotic dehydration (OD) as pretreatment and conventional air-drying. The optimum OD processing conditions (process time/temperature, concentration of osmotic solution, food to OD agent ratio) were determined through a kinetic study of the effect of OD parameters on the water activity (aw) and water/solid transport phenomena, organoleptic and quality characteristics of the white cheese in cubes. Through Fick's second law for mass transfer, water and solid diffusion coefficients were determined. Taking into consideration the aw, the quality, and organoleptic characteristics of the final product, the optimum OD conditions were selected as 15 °C process temperature, food to osmotic agent ratio 1:4 (w/w), concentration of osmotic agent 65% to glycerol, and treatment time 30 min. The final moisture and aw of the OD-treated product were calculated as 40% and 0.88, respectively. The time of OD-pretreated product for air-drying at 40, 55, and 67 °C to 5% residual moisture was reduced by 35, 51, and 65% respectively. The selected air-drying conditions were 67 °C for 4 h. Quality parameters of the final white cheese product were studied during its storage at 15–40 °C, and the shelf life was estimated as 6 months at ambient temperature. [ABSTRACT FROM AUTHOR]

The scope of the present work was the development of an ice cream containing substantial amount of phenolic compounds by substituting sucrose by a Muscat de Hamburg grape pulp and skin matter (GPSM)-enriched bulking agent at the level of 25 to 100% w/w. Sucrose replacement by GPSM reinforced the pseudoplastic and thixotropic character of the ice cream mixes imparting weak gel-like properties (G′ > G′′). Oscillatory thermo-mechanical analysis revealed the occurrence of a β-relaxation peak at − 17 to − 12.8 °C, whilst a slight depression of the freezing point was observed. The increase in GPSM solids resulted in a significant increase in the instrumental hardness and overrun of ice cream samples, whilst it enhanced their meltdown resistance. Although GPSM boosted the nutritional value and flavour profile of the ice cream, when sucrose substitution exceeded 50%, undesirable sensory characteristics, such as coarse/grainy texture, bitterness and astringency, were detected. [ABSTRACT FROM AUTHOR]

The quality and preservation of fresh-cut fruits can be improved by applying mild, non-thermal pre-treatments, such as osmotic dehydration and high hydrostatic pressure. The aim of this study was to model the effect of the combined application of these two technologies, on the main quality attributes of peaches and apricots (sensory indices, color, texture) and microbial stability during subsequent refrigerated storage. Fresh-cut fruit spheres were osmotically treated at preselected osmotic conditions (45 °C for 45 min, wfruit/wsolution = 1/5) (OD samples) and by in-pack cold-pasteurization (HP: 600 MPa/25 °C/5 min) (OD/HP samples) and stored at isothermal (5 to 15 °C) and dynamic temperature conditions (Teff = 7.8 °C). Kinetics of quality indices' change was studied and modeled as a function of storage conditions. Shelf-life was significantly prolonged for OD/HP samples, at 309 and 320 days at 4 °C, for peach and apricot, respectively, compared to approximately 68-86 days, for OD samples, limited due to microbial growth. In any case, shelf-life extension is significant, in both pretreatments (OD and OD/HP), when compared to the respective non-treated samples, with an estimated chill storage durability of 5-7 days. Apricots (both fresh and pre-treated) were softer compared to peaches. HP effect on osmosed fruit tissue was considered as positive leading to a significant increase of hardness. OD/HP samples were characterized by dark yellow to light brown color, while OD samples by vivid yellow to orange color, both evaluated positively by the sensory panel. Both pre-treated samples were described to retain to a significant level, the fresh-like fruit characteristics (aroma/flavor). [ABSTRACT FROM AUTHOR]

Most studies on frozen foods' deterioration focus on measurements of selected quality determining indices at the reference frozen storage conditions at limited time points (e.g., 6 and 12 months). This information is not sufficient to predict the frozen system behavior under a different storage temperature, or under the real, dynamic conditions of the actual cold chain. For this purpose, a systematic kinetic study is essential; additionally, the real uncertainty of model parameters needs to be taken into account, in order to proceed to realistic shelf life estimations. In this review work, published findings on kinetic data of deterioration of frozen food of plant origin were analyzed. Kinetic parameters (e.g., activation energy, shelf life, etc.) were extracted and some of them incorporated to a further investigation. The scope is to provide a critical assessment and a comprehensive meta-analysis of the literature information on quality loss modeling of frozen foods. Therefore, common quality indices for specific systems are reviewed, fundamental methodologies used to build kinetic models are assessed, and alternative approaches to improve practical applications of these models are proposed. Alternative methodologies are described in order to take into account the calculated uncertainty of models' parameters when assessing the remaining shelf life of the product at any point within the cold chain. This was implemented in a FORTRAN code through a Monte Carlo scheme, on literature data of vitamin C loss in different frozen matrices, as well as for other quality indices (e.g., color). Results demonstrated the improved predictions obtained, with broader and more realistic confidence intervals. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify and kinetically study the most high-pressure (HP) resistant deteriorative factor of gilthead seabream ( Sparus aurata) fillets aiming in their shelf life extension using in pack cold pasteurization technology. Fillets were HP processed (600 MPa, 25 °C, 5 min) and stored at 15 °C for 15 days, until spoilage. Lactobacilli were isolated from the spoiled fillets and were identified and classified as Pediococcus spp. The necessary HP process conditions for Pediococcus spp. cells inactivation were studied at various combinations of pressure (150-600 MPa) and temperature (20-40 °C) for appropriate time. The D values were calculated at all pressure-temperature combinations. The effect of temperature ( z) and pressure ( z) was estimated at all pressures and temperatures, respectively. According to the developed model for Pediococcus spp. inactivation, HP treatment of seabream fillets at 600 MPa and 25 °C for 5 min seemed to be capable for a 6-log reduction of the initial microbial load, potentially providing shelf life extension. Shelf-life experiments were conducted for validation. Untreated and HP treated at 600 MPa for 5-min samples were stored at 0, 5, 10 and 15 °C. Quality indices (colour, texture, microbial growth, sensory scoring) were monitored and kinetically modelled. Temperature dependence of quality loss rates was modelled by the Arrhenius equation. Microbial growth was well correlated with the sensory indices. HP treatment led to significant shelf life extension of fillets. Based on sensory scoring, the shelf life of the untreated samples was 11, 7, 4 and 3 days while for the HP-treated fillets 37, 27, 17 and 10 days after storage at 0, 5, 10 and 15 °C, respectively. [ABSTRACT FROM AUTHOR]

Sea buckthorn berries juice is a nutritious beverage, rich in vitamin C and carotenoids with high antioxidant activity. The main requirements for a freshly squeezed sea buckthorn juice production are the cloud stability and antioxidant activity retention after processing. Appropriate process technologies and conditions have to be applied in order to inactivate pectin methyl esterase (PME), responsible for cloud loss, while maintaining the nutritional characteristics and antioxidant activity of the juice. The objectives of the present work were to study and model the effect of thermal treatment and high pressure (HP) processing on the inactivation kinetics of endogenous PME and on total antioxidant activity alteration. Thermal treatment significantly affected PME inactivation and residual antioxidant activity. Processing even at mild process conditions (60 °C for 1 min) resulted in 2.5-fold antioxidant activity reduction and 50 % PME inactivation compared to untreated sample. Pressure and temperature acted synergistically for PME inactivation that followed first-order kinetics with a residual PME activity at all pressure-temperature combinations used (200-600 MPa and 25-35 °C). The effect of temperature and pressure on the inactivation rate constants was expressed through the activation energy and activation volume, respectively. Values of 163 kJ/mol and −17 mL/mol at reference pressure of 600 MPa and reference temperature of 35 °C were estimated, respectively. Antioxidant activity of the samples was expressed through the determination of the effective concentration (EC). A slight increase in sea buckthorn antioxidant activity when applying pressures (200-600 MPa) at ambient temperature (25 °C) was observed compared to the corresponding value of untreated juice. Processing at higher temperatures did not significantly alter the total antioxidant activity of sea buckthorn juice. For sample treated at 600 MPa-35 °C for 5 min, a 5 % reduction of total antioxidant activity was observed. These conditions are proposed as effective process conditions for sea buckthorn juice cold pasteurization, based on the higher antioxidant activity retention and simultaneous PME inactivation. [ABSTRACT FROM AUTHOR]

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A kinetic study of the inactivation of endogenous pectin methylesterase (PME) in Greek commercial peach pulp under high hydrostatic pressure (HHP; 100–800 MPa) combined with moderate temperature (30–70 °C) was conducted. Thermal inactivation of the enzyme at ambient pressure conditions was also studied. PME inactivation was modeled by first order kinetics at all conditions tested. High pressure and temperature acted synergistically on PME inactivation, except at the high temperature of 70 °C at the middle pressure range (100–600 MPa), where an antagonistic effect of pressure and temperature was observed. At this specific middle pressure range, an increase of pressure processing led to increased inactivation rate constants of peach PME. A multiparameter model was developed to express the PME inactivation rate constant as a function of temperature and pressure process conditions, taking into account the dependence of both activation energy and activation volume on pressure and temperature, respectively. A good correlation between experimental and predicted values of inactivation rate constants was established. This modeling approach enables the quantitative estimation of the HHP–temperature conditions needed to achieve a targeted PME inactivation in the peach pulp. [ABSTRACT FROM AUTHOR]