Improvement of Robusta coffee aroma by modulating flavor precursors in the green coffee bean with enzymatically treated spent coffee grounds: A circular approach.

Spent coffee grounds (SCG) are by-products obtained from the industrial process of instant coffee production or alternatively after brewing of coffee at the point of consumption. This solid residue represents one of the largest waste materials worldwide, making this fraction a rational target for valorization. The composition of SCG varies significantly depending on the brewing and extraction methods. However, this by-product is mainly composed of cellulose, hemicellulose polysaccharides and lipids. Here, we report on the enzymatic hydrolysis of industrial SCG by the use of a combination of specific carbohydrate active enzymes, enabling sugar extraction yield of 74.3 %. The generated sugar-rich extract, primarily composed of glucose (8.41 ± 1.00 % of total SCG mass) and mannose (2.88 ± 0.25 % of total SCG mass), is separated from hydrolyzed grounds and soaked with green coffee. After drying and roasting, the coffee soaked with SCG enzymatic extract displayed lower earthy, burnt and rubbery notes as well as smoother and more acidic notes in the flavor profile as compared to untreated reference. Aroma profiling performed by SPME-GC-MS corroborated the sensorial effect, with a 2-fold increase in the generation of sugar-derived molecules such as Strecker aldehydes and diketones after soaking and roasting and a 45 % and respectively 37 % reduction in phenolic compounds and pyrazines. This novel technology could represent an innovative in situ valorization stream for the coffee industry, coupled with sensory improvement of the final cup.

Hydrolysis of chicoric and caftaric acids with esterases and Lactobacillus johnsonii in Vitro and in a gastrointestinal model.

Chicoric acid (ChA) and caftaric acid (CafA) were identified as bioactive components of chicory and have been ascribed a number of health benefits. This study investigated the hydrolysis of ChA and CafA with enzymes and a probiotic bacterium Lactobacillus johnsonii (La1). Esterase from Aspergillus japonicus (24 U/mg) hydrolyzed 100% of ChA (5 mM) and CafA (5 mM) after 3 h, at pH 7.0 and 37 °C. Under the same reaction conditions, 100% hydrolysis of ChA and CafA was achieved with a spray-dried preparation of La1. The addition of La1 (100 mg/mL, 3.3 E9 cfu/g) to CafA solution in a gastrointestinal model (GI model) resulted in 65% hydrolysis of CafA. This model simulates the physicochemical conditions of the human gastrointestinal tract. No hydrolysis of CafA was observed after passage through the GI model in the absence of La1. The results of this study support the hypothesis that ChA and CafA are degraded by gut microflora before absorption and metabolization.