Advances and prospects in the food applications of pectin hydrogels

Pectin hydrogel is a soft hydrocolloid with multifaceted utilities in the food sector. Substantial knowledge acquired on the gelation mechanisms and structure-function relationship of pectin has led to interesting functions of pectin hydrogel. Food applications of pectin hydrogels can be categorized under four headings: food ingredients/additives, food packaging, bioactive delivery and health management. The cross-linked and tangly three-dimensional structure of pectin gel renders it an ideal choice of wall material for the encapsulation of biomolecules and living cells; as a fat replacer and texturizer. Likewise, pectin hydrogel is an effective satiety inducer due to its ability to swell under the simulated gastric and intestinal conditions without losing its gel structure. Coating or composites of pectin hydrogel with proteins and other polysaccharides augment its functionality as an encapsulant, satiety-inducer and food packaging material. Low-methoxyl pectin gel is an appropriate food ink for 3D printing applications due to its viscoelastic properties, adaptable microstructure and texture properties. This review aims at explaining all the applications of pectin hydrogels, as mentioned above. A comprehensive discussion is presented on the approaches by which pectin hydrogel can be transformed as a resourceful material by controlling its dimensions, state, and rheology. The final sections of this article emphasize the recent research trends in this discipline, such as the development of smart hydrogels, injectable gels, aerogels, xerogels and oleogels from pectin.

Unraveling the science of coffee foam - a comprehensive review

Coffee foam is the frothy layer that forms above the liquid phase of espresso and instant coffee beverages. While the carbon dioxide formed during roasting is responsible for crema formation in espresso, gasification is the established foaming approach in instant coffee. The protein-like fractions and polysaccharides extracted from roasted coffee promote foamability and foam stability, respectively. Crema of consolidated texture retains the volatile aromatic substances and prevents the espresso from cooling too rapidly. Further, an inverse relationship has been observed between foam persistence and volatility of aroma molecules above the cup. Gasified spray-dried instant coffee exhibited an accelerated delivery rate of hydrophobic aroma compounds. Thus, foam is the signature of a high-quality cup of coffee. Despite its various functionalities, coffee foam is scarcely investigated owing to its metastable nature. Only recently, the chemical, structural, and interfacial rheology properties of the coffee foam have been looked at. The current study intends to review the scientific knowledge acquired on coffee foam, thus far. The initial sections describe the general attributes and functions of espresso and instant coffee foam. Further, the mechanisms of formation and stabilization of coffee foam are detailed, followed by the factors influencing the same. The following discussions focus on the role of coffee foam in determining the sensory and aroma release characteristics of the beverages. The scope for future research in this field of study is highlighted in the concluding section.