Carbohydrates as targeting compounds to produce infusions resembling espresso coffee brews using quality by design approach.

All coffee brews are prepared with roasted coffee and water, giving origin to espresso, instant, or filtered coffee, exhibiting distinct physicochemical properties, depending on the extraction conditions. The different relative content of compounds in the brews modulates coffee body, aroma, and colour. In this study it was hypothesized that a coffee infusion allows to obtain extracts that resemble espresso coffee (EC) physicochemical properties. Carbohydrates (content and composition) were the target compounds as they are organoleptically important for EC due to their association to foam stability and viscosity. The freeze-drying of the extracts allowed better dissolution properties than spray-drying. Instant coffee powders were obtained with chemical overall composition resembling espresso, although with lower lipids content. The extracts were able to produce the characteristic foam through CO2 injection or salts addition. Their redissolution at espresso concentration allowed a viscosity, foamability and volatile profile representative of an espresso coffee, opening new exploitation possibilities.

In Vitro Hypocholesterolemic Effect of Coffee Compounds.

(1) Background: Cholesterol bioaccessibility is an indicator of cholesterol that is available for absorption and therefore can be a measure of hypocholesterolemic potential. In this work, the effect of commercial espresso coffee and coffee extracts on cholesterol solubility are studied in an in vitro model composed by glycodeoxycholic bile salt, as a measure of its bioaccessibility. (2) Methods: Polysaccharide extracts from coffees obtained with different extraction conditions were purified by selective precipitation with ethanol, and their sugars content were characterized by GC-FID. Hexane extraction allowed us to obtain the coffee lipids. Espresso coffee samples and extracts were tested regarding their concentration dependence on the solubility of labeled 13C-4 cholesterol by bile salt micelles, using quantitative 13C NMR. (3) Results and Discussion: Espresso coffee and coffee extracts were rich in polysaccharides, mainly arabinogalactans and galactomannans. These polysaccharides decrease cholesterol solubility and, simultaneously, the bile salts' concentration. Coffee lipid extracts were also found to decrease cholesterol solubility, although not affecting bile salt concentration. (4) Conclusions: Coffee soluble fiber, composed by the arabinogalactans and galactomannans, showed to sequester bile salts from the solution, leading to a decrease in cholesterol bioaccessibility. Coffee lipids also decrease cholesterol bioaccessibility, although the mechanism of action identified is the co-solubilization in the bile salt micelles. The effect of both polysaccharides and lipids showed to be additive, representing the overall effect observed in a typical espresso coffee. The effect of polysaccharides and lipids on cholesterol bioaccessibility should be accounted on the formulation of hypocholesterolemic food ingredients.

Impact of microwave-assisted extraction on roasted coffee carbohydrates, caffeine, chlorogenic acids and coloured compounds.

Microwave-assisted extraction (MAE) allows to quickly achieve soluble compounds from solid matrices due to the promotion of temperatures higher than the solvent (atmospheric) boiling point, once a closed-vessel system is used for operating at high pressure. In this study, the feasibility of MAE for producing high yield coffee extracts with properties that allow their commercial application was tested through a quality by design approach. It was studied the influence of time of extraction (1, 5.5, 10 min), temperature (120, 150, 180 °C) and the mass-to-volume (m/V) ratio (2, 4, 6 g/60 mL) in the overall extraction yield (24-47%, w/w), carbohydrates content (18-43%, w/w), sugars composition, caffeine (4-7%, w/w), 5-caffeoylquinic acid (1-2%, w/w), colour and antioxidant activity of the extracts. FTIR analysis was used to study the resemblance of coffee extracts and commercial instant coffee. MAE allowed overall extraction yields considerably higher than the home brewing methods, mainly when performed at 180 °C, with a substantial increase in arabinogalactans (AG) extraction associated to higher temperatures. Temperature exerted a crucial role in coffee extracts differentiation, although time and m/V ratio also lead to different values in the responses. Under a circular economy concept, MAE was able to produce extracts that can be used as defined food/brew ingredients and provides a galactomannan and cellulose rich residue that can also be valued as a source of dietary fibre.

Structural polymeric features that contribute to in vitro immunostimulatory activity of instant coffee.

An instant coffee fraction, rich in arabinogalactans, obtained by ultrafiltration, using 1 and 5kDa membranes, has previously shown in vitro stimulatory activity on BALB/c mice spleen B lymphocytes. The compounds inducing lymphocytic activation were shown to elute, mainly near the void volume by size-exclusion chromatography, using Bio-Gel P6 (1-6kDa). Treatment of the compounds with chymotrypsin, a digestive protease, did not affect the induced B lymphocyte activation. On the contrary, hydrolysis with an α-l-arabinofuranosidase, removing single terminally-linked arabinose residues, decreased the extent of B cell activation. The immunostimulatory activity of these compounds was also observed by in vitro experiments, using bone marrow-derived macrophages and dendritic cells as responders. Altogether, these results show the relevance of single arabinose residues, present at the non-reducing end of polymeric compounds, to the coffee stimulatory activity in cells mediating innate and acquired immunity.