Dietary intake and tailored fermentation towards the development of functional cereal fibre-rich food products

: bridge between Africa and Europe

Abstract

Diets rich in high-sugar and -fat foods and poor in vegetable food products have been leading to the promotion or worsening of non-communicable diseases, whereas the consumption of vegetable products, namely whole grains, has been associated with beneficial effects on consumers’ health, with high fibre content being one of the main factors involved. In addition to the undeniable importance that the assessment of the dietary intake has in the design of strategies for the promotion of more balanced eating habits, the food industry is also a key player in this context. The development of food products with beneficial health properties is the first step for an effective consumption. Therefore, it is necessary to invest research efforts towards the development of innovative, functional food products, with a high-quality nutritional profile and tailored to consumers’ needs.
In this sense, this Ph.D. thesis responds to these two research areas in the fields of food science and nutrition, proposing a two-fold strategy based on the following objectives: to study the dietary intake of adult urban Kenyans, and further comparison with Portuguese data; and, to develop and characterize an innovative fermented gluten-free whole grain-based product, with functional properties and an improved nutritional profile, expecting a positive impact on the nutritional deficits of the populations under study.
Regarding the first objective outlined within this research work, a semi-quantitative food frequency questionnaire (FFQ) was firstly designed and developed, towards its further application in the target population. Once developed, this FFQ was validated (against three non-consecutive twenty-four hours recalls) and studied for its reproducibility (test-retest method). The developed FFQ presented higher nutrient intakes compared to the multiple recalls (median for total energy: 2998 kcal vs. 2032 kcal), thus showing moderate agreement between the classification of intake quartiles; nevertheless, it was shown to be a valid and reproducible (total energy median: 2978 kcal vs. 2506 kcal) tool for ranking Kenyan urban adults according to their dietary intake. This validated FFQ was then used for the study of the dietary intake of a wider heterogeneous and representative sample of urban adult Kenyans. Macronutrients’ intake ranges were within the WHO/FAO dietary guidelines. Cereals and grain products (34.0 %), sugar, syrups, sweets, and snacks (9.8 %), fruits (9.7 %), and meat and eggs (8.8 %) were the major contributors to total energy. Individual characteristics such as gender, age and level of education seemed to have implications on the choice of food groups. When compared to the Portuguese diet, the Kenyan diet was similar in terms of contributors to energy, but with some differences regarding food sources.
Responding to the second objective, several bacterial strains (indigenous exopolysaccharides (EPS)-producing strains and commercial probiotics), in plain and combined cultures, were studied for fermentation of three different whole grain African flours, Sorghum, Pearl millet and Finger millet, expecting the selection of a bacterial consortium which would reveal fermentative capacity and after all show a positive impact on the physicochemical, nutritional, sensorial, biological profiles, and also on the human gut microbiota of the product under study. The selected bacterial consortium included the Lactiplantibacillus plantarum 299v probiotic strain and the EPS-producing Weissella confusa 2LABPT05 indigenous strain, inoculated in a 1:1 ratio (v/v), in finger millet suspended in an aqueous sucrose-based solution at 10 %, fermented at 30 ºC, 200 rpm, for 8 h. The final product obtained, hereinafter referred to as fermented yoghurt-like beverage (YLB), was shown to promote a significant growth of both strains (>108 colony-forming unit (CFU)/mL), and to have higher viscosity (35 vs. 12 mPa.s), significant EPS content (16 % vs. 0.3 %) contributing to matrix texturization and essential and non-essential amino acids (threonine, arginine, GABA, and glutamine), increased protein digestibility (64 % vs. 25 %) and high fibre content (4 g/100 g) comparatively to the native cereal prior fermentation. It was organoleptically acceptable, both per si and combined with a dairy matrix, an unsweetened plain yogurt. In terms of biological activity, antidiabetic activity (21 % vs. 14 %) and total phenolics (244 vs. 181 mg of gallic acid equivalents (GAE)/kg YLB) increased with fermentation. The digested fermented YLB contributed to the increase, during the first 6 h of feacal fermentation, of the Bifidobacterium’s number of copies of the 16S rRNA gene, which results were supported by the acidification, concomitant with an expressive metabolic activity reflected in the significant production of lactic acid and the acetic, propionic and butyric short chain fatty acids.
In conclusion, this research work has created useful nutritional epidemiology tools that can be applied in future studies carried out in Kenya. In addition, it has increased food alternatives in the
area of fermented probiotic products, specifically with the development of a novel synbiotic functional fermented African gluten-free cereal-based product. Thus, the work developed in this thesis brought
increased scientific knowledge and pioneering novelty in several areas of research.

Date of Award	26 Jul 2021
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Elisabete Pinto (Supervisor) & Ana Maria Gomes (Co-Supervisor)