Effects of alkali treatment and heat treatment in the presence of fructose on digestibility of food proteins as determined by an immobilized digestive enzyme assay (IDEA)

Abstract

An immobilized digestive enzyme assay (IDEA) system composed of two bioreactors, one containing pepsin and the other trypsin, chymotrypsin, and intestinal mucosal peptidases, was used to assess changes in protein digestibility resulting from alkali treatment or heat treatment in the presence of fructose. The degree of amino acid racemization and the amount of lysinoalanine (LAL) formed due to alkali treatment were determined. A linear correlation (r = 0.84) was obtained between loss of digestibility and the sum of the effects of both LAL formation and racemization. The effect of Maillard reactions on both digestibility, as measured with the IDEA system, and available lysine also was assessed. A linear correlation (T = 0.87) between loss of digestibility and loss in available lysine was obtained. These data indicate that the IDEA system is quite sensitive to protein modifications resulting from alkali treatment or Maillard reactions and may be a good predictor of in vivo digestibilities of processed proteins.

STABILITY OF PEPSIN (EC 3.4.23.1) DURING IN VITRO PROTEIN DIGESTIBILITY ASSAY2

“…[Pi] is calculated by the initial pepsin concentration divided by the average molecular weight of amino acids (1 15 Da). The degree of hydrolysis (DH, %) of pepsin was calculated with the following formula derived from the calculation of food protein digestibility (Chung et al 1986):…”

Stability of a Pancreatic Enzyme Cocktail During in Vitro Protein Digestibility Assays

“…1983). For convenience of data analysis, the digestion of enzymatic proteins was expressed as degree of hydrolysis (Adler‐Nissen 1986a) and calculated using the formula of Chung et al. (1986).…”

“…The enzymatic protein digestion of the pancreatic enzyme cocktail was measured spectrophotometrically with the OPA method (Church et al 1983). For convenience of data analysis, the digestion of enzymatic proteins was expressed as degree of hydrolysis (Adler-Nissen 1986a) and calculated using the formula of Chung et al (1986). Enzymatic protein concentration used in the calculation equaled the concentration of the enzyme cocktail multiplied by the protein content of the enzyme cocktail (protein content: 72%).…”

Bacteria in the ageing gut: did the taming of fire promote a long human lifespan?

“…Other consequences of cooking food have less often been taken into consideration. For example, cooking has effects quite similar to those created by alkali treatment, resulting in racemization and cross‐linking of amino acids, rapid isomerization of l ‐aspartate and l ‐asparagine, concomitant with protein aggregation and decreased digestibility of amino acids present in the overcooked parts of food (Chung et al ., ). These chemical alterations may also play a key role in physiological outcomes related to protein metabolism and longevity.…”