Development of sustainable novel foods based on coffee by-products for chronic diseases

Resumo

At present, the global obesity epidemic is showing no signs of abating, which is fuelling an explosion in numbers of type 2 diabetes (T2D) worldwide. In order to control these two associated diseases, lifestyle modification, which encompasses diet, physical activity, and healthy habits, might be useful. Several studies have focused the attention on modifying the main nutrients of the diet to reduce body weight and to enhance blood glycaemia among other metabolic biomarkers. The use of bioactive compounds obtained from vegetable sources might be a favourable approach to reduce the risk of metabolic chronic diseases; however, it is still a challenge to face. Coffee silverskin (CS) and spent coffee grounds (SCG) are very abundant coffee wastes worldwide generating global environmental problems. They are natural sources of several bioactive compounds with potential to reduce the risk of chronic non-communicable diseases, such as chlorogenic acid (CGA), caffeine and dietary fibre. The widespread interest in select foods that might promote health has resulted in the use of functional foods to provide specific health benefits beyond basic nutrition. Therefore, these coffee wastes may become sustainable high value-added ingredients of interest for the management of obesity and T2D. The present PhD thesis aimed to produce sustainable high sensorial quality beverage and foods, for reducing the risk of chronic metabolic diseases, by means of employing as novel ingredients coffee by-products (CS and SCG) and their derivatives, in combination with other functional ingredients. In addition, the present investigation search for studying the impact of the digestive process of these functional foods containing coffee by-products, on the release of satiety hormones; as well as, the implication of this physiological event on the formation of potential harmful compounds such as Maillard reaction products (MRPs). For the first time, the application of CS for the elaboration of a high sensorial quality and sustainable antioxidant beverage was proposed. CS extract (CSE)-containing beverages possessed suitable nutritional quality regarding the content of soluble dietary fibre, proteins and glycaemic sugars. Physiologically effective concentrations of bioactive compounds such as CGA and caffeine were detected in the beverages, which have shown to contribute in the reduction of fat deposits in the worm model of Caenorhabditis elegans. The beverage prepared with Robusta CSE (RCSE), at 10 mg/ml, was the most effective dose, achieving a body fat reduction of 24%. Moreover, this beverage presented similar effect on body fat accumulation to that exerted by a commercial decaffeinated green coffee supplement. Furthermore, the feasibility of the combined use of non-nutritive sweetener and CS, in order to achieve healthier, nutritious and good quality biscuits, was also investigated. CS was used as a natural colouring and as a source of dietary fibre, leading to full recovery of this coffee waste. The texture and nutritional properties of the biscuits were also improved, and the typical golden colour expected of the baked products was obtained. The formation of the food processing contaminant, hydroxymethylfurfural (HMF), was greatly reduced and no bioaccessible acrylamide was detected in the digests of the CS-containing biscuits. On the other hand, this is the first time that SCG from the instant coffee process have been proposed as sustainable natural source of antioxidant insoluble dietary fibre. Its application as food ingredient in bakery products was patented (WO2014128320 A1) during the development of the PhD thesis. The coffee fibre was exhausted of sugars, and presented small levels of processing contaminants and free bioactive compounds (CGA and caffeine), as a consequence of the extraction process in the preparation of soluble coffee beverage. The coffee fibre resisted the baking conditions and the abiotic gastrointestinal digestion in vitro. All these findings mean that SCG might be considered a source of dietary fibre. Non-nutritive sweeteners (stevia and maltitol) and fructooligosaccharides (FOS) were added to biscuits, which contain antioxidant coffee fibre, to obtain bakery products that meet consumers’ preferences. No significant differences were found with those commercial biscuits presenting high consumer adhesion and similar characteristics in terms of nonnutritive sweeteners and dietary fibre content. The novel coffee fibre-containing biscuit (CFB) presented reduced levels of food processing contaminants. Value of acrylamide (166 µg acrylamide/kg) was 67% less than the indicative values established by the European Commission in biscuits. A 4-fold decrease in the compounds associated to diabetes, such as advanced glycation end products (AGEs), was also detected compared to a sucrose-containing biscuit (SCB). The digest obtained from simulated human digestion of the CFB presented significantly (p < 0.05) lower glycaemic sugar content (60.6 mg/g) and a higher antioxidant capacity (15.1 mg CGA/g) than SCB. Antidiabetic and satiety effects were described for the CFB. The bioaccessible fraction of the CFB digest presented significantly (p < 0.05) higher inhibitory effect on α-glucosidase activity (IC50 = 3.3 mg/ml) than the SCB (IC50 = 6.2 mg/ml), and promoted the release of satiety hormones, serotonin and glucagon-like peptide-1 (GLP-1) by Caco-2 and HuTu-80 cells, respectively (355% and 278%), in the same order of magnitude as the SCB. The formation of MRPs during digestive process of simplified meal systems was for the first time examined. Our results support the formation of non-fluorescent AGEs associated to the pathogenesis of diabetes during the digestion of model systems mimicking sugar-containing and average meals, respectively. Decrease of lysine (11.7-34%), arginine (24-35%) and other essential amino acids involved in key physiological events occurred during the digestion process affecting their bioavailability. Fructosamine (42.6 and 332.9 µg/ml) and fluorescent adducts (22270 and 9283 RFU) were detected in digests of those meals containing high-fructose corn syrup (HFCS) and starch, respectively. Carboxymethyl-lysine (CML) (5 µg/ml) and methylglyoxal (MGO)-derivative AGEs (12.2 µg/ml) were found in the meal systems composed of fructose. In conclusion, the findings derived from the present PhD thesis demonstrate the feasibility of using coffee by-products, CS and SCG, in the development of novel sustainable beverages and foods with enhanced technological, nutritional and sensorial quality. Technological strategies were achieved for valorisation of coffee by-products into novel health promoting food ingredients, avoiding the production of new industrial wastes. Scientific evidences regarding the potential of the sustainable beverages and foods for reducing the risk of obesity and T2D were obtained. The novel beverages and foods decreased body fat deposits in vivo, induced the release of satiety hormones related to the feeling of fullness in gut cells (Caco-2 and HuTu-80) and exhibited inhibitory effect on αglucosidase activity in vitro. Finally, preliminary data on the impact of the digestive process of an average and sugary meal systems suggested the formation of compounds of interest in health and diseases in the intestinal lumen.