Maite Cháfer

Vacuum impregnation and osmotic dehydration in matrix engineering: Application in functional fresh food development

Abstract Health benefits are one of the specific issues that will greatly influence the food industry in the next few years. Functional foods are products that may provide a health benefit beyond the traditional content of nutrients, or through other added physiologically active components (PAC). Fruits and vegetables are increasingly being consumed because of their appreciated nutritional and fresh properties. The enrichment of these products with minerals, vitamins or other PAC can be a good choice to develop functional foods. Vacuum impregnation (VI) allows to introduce controlled quantities of a solution in the porous structure of fruit and vegetable (matrix). This solution can contain PAC, a w or pH depressors, antimicrobials, etc., in order to formulate functional, stable, fresh-like products. The feasibility of VI for a great quantity of fruits and vegetables is discussed by means of analysing their response to VI. Porosity and VI effectiveness of impregnated products were observed by Cryo-SEM. A model to determine the concentration level of PAC in the impregnating solution was established in order to formulate functional foods with different calcium and iron salts which could represent a determined percentage of the recommended daily intake of these minerals.

Influence of substituting milk powder for whey powder on yoghurt quality

Abstract Milk whey is an important source of lactose, calcium, milk proteins and soluble vitamins, which make this product be considered as functional food and a source of valuable nutrients. In this work, whey powder was used to substitute partially the milk powder in yoghurt fortification. Five different formulations were obtained and analysed for acidity, pH, gel consistency and microstructure and flow behaviour, colour (CIE L*, a*, b*) and syneresis index, after 1, 15 and 28 storage days at 5°C. Sensory properties were also evaluated after 15 storage days. Results show that the use of whey powder implies a slower acidification rate in yoghurts which becomes a little yellowish. They also show a better flow properties and greater syneresis than those obtained for products prepared with skim mil powder. Yoghurt samples with highest WP percentage (3.64–5.20%) were preferred by the sensorial panel.

Effect of amylose:amylopectin ratio and rice bran addition on starch films properties.

The influence of the amylose:amylopectin ratio on the properties of pea, potato and cassava starch films and the effect of the incorporation of rice bran of two different particle sizes were studied. The structural, mechanical, optical and barrier properties of the films were analyzed after 1 and 5 weeks. The high content of amylose gave rise to stiffer, more resistant to fracture, but less stretchable films, with lower oxygen permeability and greater water binding capacity. Although no changes in the water vapour permeability values of the films were observed during storage, their oxygen permeability decreased. Throughout storage, films became stiffer, more resistant to break, but less stretchable. Rice bran with the smallest particles improved the elastic modulus of the films, especially in high amylose content films, but reduced the film stretchability and its barrier properties, due to the enhancement of the water binding capacity and the introduction of discontinuities.

Fungal decay and shelf life of oranges coated with chitosan and bergamot, thyme, and tea tree essential oils.

UNLABELLED Chitosan coatings, containing or not essential oils (bergamot, thyme and tea tree oil), were applied to oranges (cv. Navel Powell). Antifungal effect was evaluated by applying coatings before and after inoculating the fruit with Penicillium italicum CECT 2294 (10(5) spores/mL), preventive and curative treatments, respectively. The effect of coatings on the quality parameters (acidity, pH, soluble solids, juice percentage, weight loss, firmness, color parameters, and respiration rate) was controlled for the different oranges samples throughout the cold storage time. Preventive antimicrobial treatments with coatings containing tea tree oil were the most effective with a reduction of the microbial growth (expressed as the percentage of infected samples) of 50%, as compared to the uncoated samples. The coatings did not lead to any relevant changes in the development of the sample quality parameters throughout the cold storage, except for a slightly reduced loss of both weight and firmness when the coatings contained bergamot oil. PRACTICAL APPLICATIONS Results of this study are a useful tool for the development of new environmental friendly and healthier commercial applications in the control of the main postharvest fungal decay of citrus fruits.

Microstructure and vacuum impregnation response of citrus peels

Abstract Vacuum impregnation (VI) technique represents a good choice for developing high quality peel products or food ingredients, taking advantage of their interesting composition, increasing their sweetness and improving their sensory acceptance. Vacuum impregnation response of citrus peels (orange, mandarin, lemon, grapefruit) were analysed using different isotonic solutions. Sample deformation and impregnation levels in line with pressure changes have been determined. Peel microstructure has also been analysed (by Cryo-SEM) before and after the VI process. Results reflect a high capacity of impregnation (45–70% of initial sample volume) and swelling (12–33% of initial sample volume) of the peels. The great porosity of the albedo zone is responsible for this behaviour. In this zone, the great intercellular spaces can be flooded by an external solution, and this makes the citrus peels highly suitable to obtain new products with improved functionality and sensory acceptance.

Effect of Blanching and Vacuum Pulse Application on Osmotic Dehydration of Pear

Osmotic dehydration of pear cylinders (var. blanquilla) was studied by analysing the effect of blanching pre-treatment and the application of a vacuum pulse on the kinetics and yield of the process and on product quality (colour and mechanical behaviour). Fresh and stem-blanched samples were treated with 65 Brix sucrose at atmospheric pressure and by applying a vacuum pulse (50 mbar for 5 min). The influence of the sugar gain and water loss fluxes, and the tissue structural response to the vacuum pulse, on the total mass and volume losses of the samples has been discussed. Blanching implied an increase in the mass transfer rate in pear tissue. Vacuum pulse in blanched samples resulted in more volume compression than sample impregnation with the external solution due to the sample softening by thermal effect and to the partial gas release during its thermal expansion. This provoked the greatest volume losses and a reductionof the ratio of sugar gain to water loss, where the highest values reached were for non-blanched samples submitted to vacuum pulse. Mechanical changes induced by treatments were similar inall cases, but colour hue and chrome were better preserved in samples treated by PVOD. Nevertheless, this treatment implied a transparency gain due to the sample gas release and so, samples become darker.

Development of salt profiles on Manchego type cheese during brining. Influence of vacuum pressure

Abstract Cheese brining is a slow process, consistent with the low values of salt diffusivity through the liquid phase trapped in the protein matrix, especially at low temperatures. The action of hydrodynamic mechanisms (HDM) in the porous protein matrix might accelerate mass transport by introducing brine directly in the pores. Promotion of HDM occurs when pressure gradients are applied to the system (e.g. applying vacuum). The influence of pressure in the system on the developing salt concentration profiles during brining of Manchego type cheese was analysed. Salting was carried out at atmospheric pressure (BI), at vacuum pressure (50 mbar) (VI) and by applying a vacuum pulse at the beginning of the process which then continued at atmospheric conditions (PVI). In VI brining, the developed salt concentration profiles can be better modelled by an advancing disturbance front model than by diffusional equations. Curd porosity and moisture greatly affected salt transport kinetics, in this case.

Long Term Osmotic Dehydration Processes of Orange Peel at Atmospheric Pressure and by Applying a Vacuum Pulse

Osmotic dehydration is a useful tool to obtain orange peel products with good sensory acceptance and stability. Osmodehydration of orange peel has been carried out in different osmotic solutions (65 Brix sucrose, 55 Brix glucose and concentrated rectified grape must) at 40 and 50 C for different durations (0–10 days), at atmospheric pressure and by applying a vacuum pulse at the beginning of the process. Changes in sample composition (water and soluble solid contents), weight, volume, density and porosity were analyzed. In all conditions, samples reached the same sample solute content as the osmotic solution at about 24 h of treatment, and the concentration rate was faster when vacuum pulse was applied. Mass transfer behavior showed that impregnation of the peel pores occurred to a great extent, not only when applying vacuum pulse, but also in treatments at normal pressure, due to the capillary effects and pressure gradients generated in the tissue associated with structural changes. Impregnation contributed to compositional changes and weight development of the sample. The greater the osmotic solution viscosity, the lower the impregnation level at equilibrium, which was always promoted by vacuum pulse.

Kinetics of Solute Gain and Water Loss During Osmotic Dehydration of Orange Slices

The effect of the osmotic solution (sucrose and dextrose syrups) on the kinetics and process yield was evaluated on osmotic dehydration of orange (Valencia Late var.). Processes were carried out at 30 C, using 35, 45, 55 and 65 Brix solutions and by applying a vacuum pulse (100 mbar for 10 min) at the beginning of the process. Kinetics of sugar gain-water loss and mass changes were analysed by separately considering peel and pulp fractions of orange slices. Mass transport properties of orange slices in osmotic treatments were different for pulp and peel fractions due to the different contributions of the mechanisms involved. Faster water and solute transport were observed in the peel impregnated with the osmotic solution. Sugar gain in sucrose solutions was enhanced in comparison with dextrose treatments, whereas diffusional water loss was faster in samples treated with dextrose. These effects made the process yield higher for sucrose treatments. An increase in the osmotic solution concentration implied higher mass transport rates, but did not notably affect process yield.

Optimisation of oat milk formulation to obtain fermented derivatives by using probiotic Lactobacillus reuteri microorganisms

Functional advantages of probiotics combined with interesting composition of oat were considered as an alternative to dairy products. In this study, fermentation of oat milk with Lactobacillus reuteri and Streptococcus thermophilus was analysed to develop a new probiotic product. Central composite design with response surface methodology was used to analyse the effect of different factors (glucose, fructose, inulin and starters) on the probiotic population in the product. Optimised formulation was characterised throughout storage time at 4 ℃ in terms of pH, acidity, β-glucan and oligosaccharides contents, colour and rheological behaviour. All formulations studied were adequate to produce fermented foods and minimum dose of each factor was considered as optimum. The selected formulation allowed starters survival above 107/cfu ml to be considered as a functional food and was maintained during the 28 days controlled. β-glucans remained in the final product with a positive effect on viscosity. Therefore, a new probiotic non-dairy milk was successfully developed in which high probiotic survivals were assured throughout the typical yoghurt-like shelf life.