Degree of Digestibility of Barley Rice Proteins

Barley rice protein is extracted from brewer spent grains (BSG), which is the most voluminous by-product of the brewing industry. Until now, BSG has been mainly used for animal feed or is directly discarded, which is an enormous waste of resources and causes serious environmental pollution. BSG is rich in cellulose and non-cellulosic polysaccharides, lignin, and proteins. The protein fraction of BSG contains a relatively high content of the essential amino acid, lysine, in comparison to other cereal products. Because of its high nutritional content, BSG can be applied in human food products for fortification. The digestion characteristics of barley rice protein are not known, but essential to evaluate their future potential as a sustainable protein source.

The primary objective is to estimate the degree of digestibility of barley rice protein by measuring post-prandial amino acid uptake kinetics, and compare this to pea protein and a benchmark protein (whey).

Secondary objectives are to assess the effects on blood glucose and insulin levels.

The study is a randomized, cross-over, double blind, controlled trial. Three different treatments, all representing a 20g protein load, will be evaluated with a washout period of minimum one week between the test days. Blood will be collected via a catheter before and up-to five hours after protein consumption. Wellbeing, health complaints or other adverse effects will be collected via a short questionnaire during each test day. After each test day gastrointestinal complaints are collected via an online questionnaire.

Inclusion criteria

• Apparently healthy men and women;
• Age between 18 and 40 years;
• Body mass index (BMI) between 18.5 and 30 kg/m2 ;
• Having veins suitable for blood sampling via a catheter (judged by study nurse/ medical doctor).

Exclusion criteria

• Any metabolic, gastrointestinal, inflammatory or chronic disease (such as diabetes, anaemia, hepatitis, cardiovascular disease),or having a condition or disease that may lead to an impaired immune system;
• History of gastrointestinal surgery or having (serious) gastrointestinal complaints;
• History of liver dysfunction (cirrhosis, hepatitis) or liver surgery;
• Kidney dysfunction (self-reported);
• Any use of medication that may suppress the immune system, this will be judged by the medical supervisor;
• Use of medication that may influence the study results, such as gastric acid inhibitors, laxatives, stomach protectors and drugs that can affect intestinal motility, this will be judged by the medical supervisor;
• Anaemia (Hb values <7.5 mmol/L for women and <8.5 mmol/L for men);
• Reported slimming, medically prescribed or other extreme diets;
• Use of protein supplements;
• Not willing to give up blood donation during the study;
• Current smokers;
• Alcohol intake ≥4 glasses of alcoholic beverages per day;
• Pregnant, lactating or wishing to become pregnant in the period of the study (self-reported);
• Abuse of hard drugs;
• Having food allergies and/or intolerances (e.g. for gluten);
• Not having a general practitioner;
• Participation in another clinical trial at the same time;
• Being an employee of the department Food, Health & Consumer Research of Wageningen Food & Biobased Research.