Acetylated pectins in raw and heat processed carrots
Broxterman, Suzanne E. ; Picouet, Pierre ; Schols, Henk A. - \ 2017
Carbohydrate Polymers 177 (2017). - ISSN 0144-8617 - p. 58 - 66.
Acetylation - Enzymatic fingerprinting - Heat processing - Homogalacturonan - MALDI-TOF MS
Heat processing results in softening of carrots, changing the pectin structure. The effect of heat processing on pectin was studied, showing that the amount of pectin in water soluble solids (WSS) and chelating agent soluble solids (ChSS) increased substantially upon heat processing of the carrots. Pectin in WSS from both unprocessed and heat processed carrot had a degree of methyl-esterification (DM) of ≈60% and a degree of acetylation (DA) of ≈20%. Enzymatic degradation released methyl-esterified galacturonic acid oligomers of degree of polymerisation ≥6 carrying acetyl groups. Mass spectrometry confirmed acetylation in highly methyl-esterified homogalacturonan (HG) regions, next to known rhamnogalacturonan (RG-I) acetylation. ChSS HGs were un-acetylated. RG-I levels of both heat processed carrot WSS and ChSS increased. Digestion of WSS with RG-I degrading enzymes showed that WSS arabinan became more linear upon heat processing resulting in the release of oligosaccharides, while in ChSS galactan became more linear.
Denaturation and in Vitro Gastric Digestion of Heat-Treated Quinoa Protein Isolates Obtained at Various Extraction pH
Ruiz, Geraldine Avila ; Opazo-Navarrete, Mauricio ; Meurs, Marlon ; Minor, Marcel ; Sala, Guido ; Boekel, Tiny van; Stieger, Markus ; Janssen, Anja E.M. - \ 2016
Food Biophysics 11 (2016)2. - ISSN 1557-1858 - p. 184 - 197.
Denaturation - Digestibility - Extraction pH - Heat processing - Protein - Quinoa
The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60, 90 and 120 °C for 30 min led to protein denaturation and aggregation, which was enhanced at higher treatment temperatures. The in vitro gastric digestibility measured during 6 h was lower for protein extracts pre-treated at 90 and 120 °C compared to 60 °C. The digestibility decreased with increasing extraction pH, which could be ascribed to protein aggregation. Protein digestibility of the quinoa protein isolates was higher compared to wholemeal quinoa flour. We conclude that an interactive effect of processing temperature and extraction pH on in vitro gastric digestibility of quinoa protein isolates obtained at various extraction pH is observed. This gives a first indication of how the nutritional value of quinoa protein could be influenced by heat processing, protein extraction conditions and other grain components.