The impact of conjugated wpi-lactose on the physicochemical and functional properties and in-vitro infant digestion

• Main Author: Sarizan Sabari
• Format: Thesis
• Language: English; English
• Published: 2023
• Subjects: TX341-641 Nutrition. Foods and food supply
• Online Access: https://eprints.ums.edu.my/id/eprint/40860/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/40860/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/40860/
• Institution: Universiti Malaysia Sabah

Proteins are crucial for body metabolism, are abundant in whey proteins isolate (WPI) with a high concentration of essential amino acids. The natural form of WPI has limitations as it is susceptible to temperature, pH changes and digestibility in gastrointestinal tract of infant. The influence of protein processing is significant but is dependent upon the variety of parameters and controlled conditions. Thus, the aim of the current study to evaluate the physicochemical and functional properties of conjugates proteins of WPI-Lactose (WPI-Lac) versus native WPI under the optimized condition (temperature of reaction is 40℃, 1,3,5 and 7 days of incubation time, 0.8 of water activity (Aw) and a protein-to-disaccharide ratio of 1:0.4) of Maillard reaction (MR). This study also investigates the impact of the conjugated proteins-lactose in proteins digestibility on infant static in- vitro digestion model. Amongst those conjugates p roteins, the WPI WPI-Lac day 3 is showed the particularly acceptable browning colour intensity of Maillard reaction products (MRPs) (0.784±0.000, 290nm), (0.197±0.000, 420nm) and have colour index (ΔE) (90.37) and chroma value (C) (17.96 ) increased with the incubation time. The conjugated proteins increased in molecular weight and were elucidated in SDS SDS-PAGE gel by slightly shifting upwards and sm earing from day 1 to day 7 on incubation time (>20 kDa). 75% of the free amino group available in WPI WPI-Lac (day 3) which indicated only 25% of leucine was conjugated with lactose and this prevent the advancedadvanced-stage reaction of MR. The conjugates protein cl early changed (p<0.05) in Amide I ( 1634.52 cm-1) and Amide II (1500 cm cm-1) from day 0 to day 7. Higher solubility of protein is shown in WPI-Lac (day 3) at 36.27%, while the ABTS+ radical scavenging activity of conjugates protein significantly increased (p<0.05) with incubation time from 10.14% (day 0) to 61.94% (day 7), respectively. In The heating treatment of WPI-Lac (day 3) by MR and conjugated with lactose under optimized conditions of MR has enhanced the digestibility of the α-Lac which were completely disappear after 5 minutes of digestion in gastric digestion. Additionally, after 60 minutes, the α-Lac of WPI-Lac (day 3) was breakdown into smaller peptides (<10kDa) as shown in the SDS-PAGE. In in-vitro duodenal digestion, β-Lg of WPI-Lac (day 3) was mostly completely degraded at 100 minutes of digestion. Thus, dry MR of protein at 40 °C for three days with 0.8 water activity and conjugated with lactose may be a useful alternative for improving the digestibility of protein in infants' digestive systems. Additionally, due to the ability of β-Lg to be digested in the duodenal digestion phase, conjugated proteins have a significant potential to give strong impact on the release of the immunogenic protein.