Ivan Salmerón

Production of potentially probiotic beverages using single and mixed cereal substrates fermented with lactic acid bacteria cultures.

In the present work, single and mixed cereal substrates were fermented with lactic acid bacteria to study and compare the effect of the media formulation on fermentation parameters. Three cereal flours namely malt, barley and barley mixed with malt (barley-malt) were selected and fermented with two probiotic strains: Lactobacillus plantarum (NCIMB 8826) and Lactobacillus acidophilus (NCIMB 8821). The effect of the single and mixed cereal flour suspensions on the fermentation of these two strains of lactic acid bacteria (LAB) was studied at an incubation temperature of 30 °C for 28 h. It was found that the LAB growth was enhanced in media containing malt and significant amounts of lactic acid were produced (0.5-3.5 g/L). A cell concentration between 7.9 and 8.5 Log₁₀ CFU/mL and a pH below 4.0 was achieved within 6 h of fermentation. Though the cell populations in the mixed culture fermentations of mixed substrates were similar to the ones obtained with single cereal flours, significant differences in the production of lactic acid were observed. These results suggest that the functional and organoleptic properties of these cereal-based probiotic drinks could be considerably modified through changes in the substrate or inocula composition.

Investigation of the factors influencing the survival of Bifidobacterium longum in model acidic solutions and fruit juices

The survival of Bifidobacterium longum NCIMB 8809 was studied during refrigerated storage for 6weeks in model solutions, based on which a mathematical model was constructed describing cell survival as a function of pH, citric acid, protein and dietary fibre. A Central Composite Design (CCD) was developed studying the influence of four factors at three levels, i.e., pH (3.2-4), citric acid (2-15g/l), protein (0-10g/l), and dietary fibre (0-8g/l). In total, 31 experimental runs were carried out. Analysis of variance (ANOVA) of the regression model demonstrated that the model fitted well the data. From the regression coefficients it was deduced that all four factors had a statistically significant (P<0.05) negative effect on the log decrease [log10N0 week-log10N6 week], with the pH and citric acid being the most influential ones. Cell survival during storage was also investigated in various types of juices, including orange, grapefruit, blackcurrant, pineapple, pomegranate and strawberry. The highest cell survival (less than 0.4log decrease) after 6weeks of storage was observed in orange and pineapple, both of which had a pH of about 3.8. Although the pH of grapefruit and blackcurrant was similar (pH ∼3.2), the log decrease of the former was ∼0.5log, whereas of the latter was ∼0.7log. One reason for this could be the fact that grapefruit contained a high amount of citric acid (15.3g/l). The log decrease in pomegranate and strawberry juices was extremely high (∼8logs). The mathematical model was able to predict adequately the cell survival in orange, grapefruit, blackcurrant, and pineapple juices. However, the model failed to predict the cell survival in pomegranate and strawberry, most likely due to the very high levels of phenolic compounds in these two juices.

Fermentation adaptability of three probiotic Lactobacillus strains to oat, germinated oat and malted oat substrates

Functional foods targeting the improvement of gastrointestinal health are widely recognized; of these, dairy‐based probiotics are the most popular. Thus, the design of nondairy probiotics applying fruits, vegetables and cereals has raised great interest in the healthy food sector. The objective of this work was to assess the potential of germinated and malted oat substrates to support the growth of the probiotic cultures Lactobacillus acidophilus, Lactobacillus casei and Lactobacillus rhamnosus. Fermentations were carried out with distinctive oat substrates at inoculum levels of 3, 5 and 7% v/v, substrate concentrations of 3, 5 and 7% w/v and with sucrose addition 1·5% w/v. Lag phase profiles, maximum growth rates and maximal growths were evaluated; protein and sugar contents were also quantified. There was no significant effect (P > 0·05) of the inoculum size on the fermentation kinetics; however, oat media significantly affected the growth kinetics. In simple oat media, Lact. acidophilus exhibited biphasic growth patterns. Lactobacillus growth patterns were significantly affected (P < 0·05) by the supplementation with protein sources. The germination and malting processes significantly improved oats nutrient characteristics demonstrating to be adequate substrates for the fermentation with probiotic lactobacilli.

Sensory characteristics and volatile composition of a cereal beverage fermented with Bifidobacterium breve NCIMB 702257

Most of the commercialized lactic acid fermented products are dairy-based. Hence, the development of non-dairy fermented products with probiotic properties draws significant attention within the functional foods industry. The microorganisms used in such products have complex enzyme systems through which they generate diverse metabolites (volatile and non-volatile) that provide significant flavour attributes of importance for fermented foods. The correlation of the volatile flavour compounds of a malt beverage fermented with a Bifidobacterium breve strain with its unique sensory characteristics was performed. The volatile composition analysis exposed the presence of 12 components. Eight of these flavour volatiles were produced through the metabolic activity of the bifidobacteria strain. Notably acetic acid, of reported sour flavour characteristics, exhibited the greatest intensity. Four components of considerable organoleptic characteristics were identified as Maillard-derived products, namely maltol, pyranone, 2 (5H)-furanmethanol and 3-furanmethanol. The sensory evaluation exhibited that the fermented cereal beverage had a sour flavour with mild sweet and malty notes. These results indicate that the volatile compounds identified can be appointed as significant flavour markers of the novel fermented cereal beverage.

Headspace gas chromatography (HS-GC) analysis of imperative flavor compounds in Lactobacilli-fermented barley and malt substrates

The kinetics of volatile flavor compounds produced during the fermentation of cereal substrates inoculated with potentially probiotic lactobacilli were determined by HSGC. Barley and malt substrates were single cultured with Lactobacillus acidophilus, Lactobacillus reuteri, and Lactobacillus plantarum. The volatile flavor profiles were unique for each of the formulations. Acetaldehyde, acetone and ethyl acetate concentrations (2.86, 1.82, and 0.39 mg/ L, respectively) were significantly higher in L. plantarum fermented malt substrates. L. reuteri produced greater values of ethanol in the malt medium (2,300 mg/L) and the three lactobacilli strains produced diacetyl only in the malt substrate. These results suggest that the cereal substrate plays a meaningful role for the production of imperative flavor compounds in Lactobacillus-fermentations. Furthermore, the enzymatic systems of particular lactobacilli strains have the ability to produce flavor compounds at concentrations that can significantly influence the organoleptic quality of non-dairy fermented products for potential development.

Ultraviolet Irradiation Effect on Apple Juice Bioactive Compounds during Shelf Storage

Clarified and standardized apple juice was ultraviolet-irradiated to inactivate polyphenol oxidase enzyme and microbiota, and its effect on bioactive compounds and stability during storage was also evaluated. Apple juice was irradiated with 345.6 J/cm2 and treatment effect was evaluated in terms of color, antioxidant capacity, polyphenol content, pH, titratable acidity and total soluble solids. Using a linear regression design, inactivation kinetic of polyphenol oxidase enzyme was also described. In addition, a repeated measures design was carried out to evaluate apple juice during 24 days of storage at 4 °C and 20 °C. After irradiation, reduction of antioxidant capacity was observed while during storage, ascorbic acid content decreased up to 40% and total polyphenol content remain stable. Ultraviolet irradiation achieved a complete inactivation of polyphenol oxidase enzyme and microbiota, keeping apple juice antioxidants during ultraviolet treatment and storage available until juice consumption. UV-treated apple juice can be used as a regular beverage, ensuring antioxidant intake.

Fermented cereal beverages: from probiotic, prebiotic and synbiotic towards Nanoscience designed healthy drinks

The consumption of fermented foods by human kind goes a long way back in history and there are as many types of fermented food as civilizations. Food Science and Technology has progressed from designing nutritional foods towards food with health improvement characteristics such as functional foods. In this sense, the area of food with properties to improve gastrointestinal health such as probiotics, prebiotics and synbiotics has been the most important segment within functional foods. Most of these products are dairy‐based so the development of nondairy gut improvement products has been of great interest for the food industry, resulting in the rise of cereal‐based probiotic and synbiotic products. Finally, through Nanoscience and the application of Nanotechnology techniques in the food sector, it has been possible to design fermented beverages with synbiotic properties, and the incorporation of nanoparticles with unique and specific bioactivity, which has opened a new horizon in this segment of food created to improve human health and well‐being.

Ultrasound-assisted crystallization of lactose in the presence of whey proteins and κ-carrageenan

The conventional process of lactose crystallization is prolonged, hardly controllable and the crystals have low quality. In this work, the effect of ultrasound on the crystallization of lactose in an aqueous system was assessed. Additionally, it was studied how the presence of whey proteins (which are a common impurity) and κ-carrageenan (that possess high water-binding capacity) could modify the process of lactose crystallization. Lactose solutions at 25% were sonicated in a continuous flow chamber at two different energy densities (9 and 50 J mL-1) before the start of crystallization. Some of these lactose solutions were previously added with κ-carrageenan (0, 150 and 300 mg L-1), with whey proteins (0.64%) or with both at the same time. Ultrasound sped up the rate of crystallization, decreased the crystals size and narrowed the crystal size distribution (CSD). The presence of whey proteins accelerated the process of crystallization but induced the formation of amorphous lactose. Likewise, the rate of lactose crystallization was improved by the addition of 150 mg L-1 of carrageenan. Whereas, the combination of carrageenan and whey proteins generated the smallest crystals (6 μm), the narrowest CSD and minimized the formation of amorphous lactose.