Unraveling the science of coffee foam - a comprehensive review

Valorization of faba bean peels for fungal tannase production and its application in coffee tannin removal

This study describes the optimization of the production conditions of Penicillium commune tannase on unutilized food waste, green bean peels, using the central composite of the response surface methodology. It also focuses on applying purified tannase to reduce tannins in coffee. The proposed design recommended a temperature of 29.07 °C, pH of 6.74, a tannin level of 6.76%, and 3.31% bean peels for maximum tannase production (313.40 U/g/min) by solid-state fermentation. This waste can be used as a sustainable and low-cost substrate for tannase enhancement by ≈5 folds. Applying purified tannase in instant coffee beverage resulted in a ≈ 23% reduction in tannins and a ≈ 16% increase in reducing sugars, with no significant changes in caffeine and phenolic compound contents. Tannase had a detrimental effect on the volume and stability of the coffee foam. This study will pave the way for tannase industrial production and its promising use in low-bitter coffee production.

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

Foam, as a structured multi-scale colloidal system, is becoming increasingly popular in food because it gives a series of unique textures, structures, and appearances to foods while maintaining clean labels. Recently, developing green and healthy food-grade foaming agents, improving the stability of edible foams, and exploring the application of foam structures and new foaming agents have been the focus of foam systems. This review comprehensively introduces the destabilization mechanisms of foam and summarizes the main mechanisms controlling the foam stability and progress of different food-grade materials (small-molecular surfactants, biopolymers, and edible Pickering particles). Furthermore, the classic foam systems in food and modern cuisine, their applications, developments, and challenges are also underlined. Natural small-molecular surfactants, novel plant/microalgae proteins, and edible colloidal particles are the research hotspots of high-efficiency food-grade foam stabilizers. They have apparent differences in foam stability mechanisms, and each exerts its advantages. However, the development of foam stabilizers remains to be enriched compared with emulsions. Food foams are diverse and widely used, bringing unique enjoyment and benefit to consumers regarding sense, innovation, and health attributes. In addition to industrial inflatable foods, the foam foods in molecular gastronomy are also worthy of exploration. Moreover, edible foams may have greater potential in structured food design, 3D/4D printing, and controlled flavor release in the future. This review will provide a reference for the efficient development of functional inflatable foods and the advancement of foam technologies in modern cuisine.

Targeted and Non-Targeted HPLC Analysis of Coffee-Based Products as Effective Tools for Evaluating the Coffee Authenticity

Coffee is a very popular beverage worldwide. However, its composition and characteristics are affected by a number of factors, such as geographical and botanical origin, harvesting and roasting conditions, and brewing method used. As coffee consumption rises, the demands on its high quality and authenticity naturally grows as well. Unfortunately, at the same time, various tricks of coffee adulteration occur more frequently, with the intention of quick economic profit. Many analytical methods have already been developed to verify the coffee authenticity, in which the high-performance liquid chromatography (HPLC) plays a crucial role, especially thanks to its high selectivity and sensitivity. Thus, this review summarizes the results of targeted and non-targeted HPLC analysis of coffee-based products over the last 10 years as an effective tool for determining coffee composition, which can help to reveal potential forgeries and non-compliance with good manufacturing practice, and subsequently protects consumers from buying overpriced low-quality product. The advantages and drawbacks of the targeted analysis are specified and contrasted with those of the non-targeted HPLC fingerprints, which simply consider the chemical profile of the sample, regardless of the determination of individual compounds present.

Investigation of the factors affecting foamability and foam stability of cold brew coffee

BACKGROUND

In this study, the foamability and foam stability of nitrogen-infused cold brew coffee, as affected by coffee variety (Arabica and Robusta), degree of roast (light, medium, dark), brewing temperature (4, 20, 35 °C), brew ratio (1:5-1:15 w/w; coffee/water), ground particle size (712, 647 and 437 μm volume mean diameter) and beverage temperature (4, 20 and 35 °C), were investigated.

RESULTS

Dynamic surface tension of cold brew, as determined from bubble tensiometry, decreased from 65-70 mN m^-1 to about 60 mN m^-1 as the bubble lifetime increased from 0.1 s to 1 s. Infusing the cold brew coffee (70 mL) with nitrogen gas for 30 s at 50 mL min^-1 generated 30-40 mL of foam head. At the same degree of roast, brews prepared from Arabica beans had more stable foam than those from Robusta. Foam stability increased with increasing degree of roast, increasing brewing temperature, decreasing particle size, and decreasing the beverage temperature. By contrast, brew ratio had relatively less effect on foaming properties. Nitrogen-containing constituents present in the 80% (v/v) ethanol-soluble fraction (55.9% of total dissolved solids) of the brew samples were important contributors to foaming, while the 80% (v/v) ethanol-insoluble fraction (42.3% of total dissolved solids) that contained polysaccharides was important in stabilizing the foam.

CONCLUSION

The foamability and foam stability of cold brew coffee are significantly affected by coffee variety, degree of roast, brewing temperature, ground particle size, and beverage temperatures. The foam properties are dictated by the low-molecular-weight nitrogen-containing compounds and high-molecular-weight polysaccharides present in the cold brew coffee. © 2022 Society of Chemical Industry.

Current strategies to guarantee the authenticity of coffee

As they become more health conscious, consumers are paying increasing attention to food quality and safety. In coffee production, fraudulent strategies to reduce costs and maximize profits include mixing beans from two species of different economic value, the addition of other substances and/or foods, and mislabeling. Therefore, testing for coffee authenticity and detecting adulterants is required for value assessment and consumer protection. Here we provide an overview of the chromatography, spectroscopy, and single-nucleotide polymorphism-based methods used to distinguish between the major coffee species Arabica and Robusta. This review also describes the techniques applied to trace the geographical origin of coffee, based mainly on the chemical composition of the beans, an approach that can discriminate between coffee-growing regions on a continental or more local level. Finally, the analytical techniques used to detect coffee adulteration with other foods and/or coffee by-products are discussed, with a look at the practice of adding pharmacologically active compounds to coffee, and their harmful effects on health.