Human digestion – a processing perspective

Abstract

The human digestive system is reviewed in the context of a process with four major unit operations: oral processing to reduce particle size and produce a bolus; gastric processing to initiate chemical and enzymatic breakdown; small intestinal processing to break down macromolecules and absorb nutrients; and fermentation and water removal in the colon. Topics are highlighted about which we need to know more, including effects of aging and dentition on particle size in the bolus, effects of different patterns of food and beverage intake on nutrition, changes in saliva production and composition, mechanical effects of gastric processing, distribution of pH in the stomach, physicochemical and enzymatic effects on nutrient availability and uptake in the small intestine, and the composition, effects of and changes in the microbiota of the colon. Current topics of interest including food synergy, gut-brain interactions, nutritional phenotype and digestion in the elderly are considered. Finally, opportunities for food design based on an understanding of digestive processing are discussed.

Which variables should be controlled when measuring the granulometry of a chewed bolus? A systematic review

“…Overall, bolus granulometry was explained by 60 variables that could be distributed in five categories: (a) Type of test (Chewing‐ or Mastication‐test); (b) Food or material chewed (type, shape, length or diameter, mass, volume, sample used number); (c) Chewing parameters (one chewing side only, side of chewing, number of strokes for granulometry analysis, number of strokes for kinematic analysis, duration of the chewing sequence, bolus granulometry analysis at the point of swallowing, chewing analysis at the point of swallowing); (d) Subjects (number of males [total in the study], average age [total in the study], standard deviation of age [total in the study], minimum age [total in the study], maximum age [total in the study], health state [in the group], number of subjects [in the group], number of males [in the group], average age [in the group], standard deviation of age [in the group], minimum age [in the group], maximum age [in the group], subjects’ dental state, number of posterior functional units); (e) Experimental procedures (number of repetitions in granulometry analysis, number of repetition in kinematic analysis, number of subjects [total in the study], number of test sessions [total in the study], time interval between two‐test sessions [total in the study], number of groups, inclusion number of the group, number of tests sessions [in the group], time interval between two tests [in the group], time of observation, study sort, measurement type, sample mass after the test, sample freezing, sample rinsing, chemical product added, sample drying, drying temperature, drying time, rinsing sieve size, physical sieving conditions [number of sieves, maximum mesh size, minimum mesh size, bottom plate used, wet sieving, mechanical shaker used, shaker time], image analysis conditions [scanner type, resolution, presieving used, presieving mesh size, assumption particles are spheres with scanner, analysis software used]). The number of strokes and dental status were most frequently used to describe the conditions for producing the bolus granulometry variability found in previous studies (Boland, ; van der Bilt, ).…”

“…Surprisingly, no studies used variables related to the content of saliva in the bolus, or of the quality and/or quantity of saliva production by the subjects. Saliva is one of the main components in the formation of the bolus before swallowing (Boland, ; Mishellany‐Dutour et al, ). It has different functions and roles in the upper part of the gastrointestinal tract and especially in the mouth: mechanical cleansing of food and bacteria, lubrication of oral and oro‐oesophageal mucosa, protection of teeth, oral acid neutralization and dilution of detritus, antimicrobial activity, dissolution of taste compounds, facilitation of speech, mastication and swallowing, formation of food bolus conducive for swallowing, initial digestion of starches and lipids, esophageal clearance, and gastric acid buffering (Pedersen, Bardow, Jensen, & Nauntofte, ).…”

Physicochemical properties and fatty acid composition of star fruit (<i>Averrohoa carambola</i>) seed oil

“…The oil yield (28.45%) is higher than 18.30-21.53% oil yield reported for various soybean cultivars (Vasconcelos et al, 1997) and lower than 45.71% for Ximenia americana seed oil (Eromosele et al, 1994) and castor seed oil 44.69% (Onukwli and Igbokwe, 2008), suggesting the classifying of Averrohoa carambola plant as an oilseed plant. The iodine value of the oil was 140.50 g I 2 100g -1 this value compares very well with that of rubber seed oil 136.20 g I 2 100g -1 (Ikhuoria and Okieimen, 2005).…”

Acute Colonic Pseudo-Obstruction with Feeding Intolerance in Critically Ill Patients: A Study according to Gut Wall Analysis

“…Therefore, ileostomy may prevent bacterial translocation besides having the merits of minimal trauma. On the other hand, since nutrition was mainly absorbed in the small bowels [33], ileostomy could make the large bowels rest and EN could be avoided in the large bowel, thus avoiding the occurrence of FI caused by colonic dysfunction which may also be secondary to colostomy or colectomy; thus, not surprisingly, ileostomy could avoid the occurrence of FI afterwards. For these reasons, patients in this study all underwent ileostomy when surgical interventions were needed, and colectomy was only applied in cases of colonic necrosis and perforation.…”