Processing Stability of Antioxidant Protein Hydrolysates Extracted from Degreased Walnut Meal

Abstract

Degreased walnut meal was hydrolyzed by trypsin and the optimal hydrolysis conditions were at the enzyme to substrate of 9.2×10 5 U/g with the hydrolysis time of 30h. The effects of acidic/alkaline treatments on the antioxidant stability of WPH (liquid walnut meal protein hydrolysate), WPHP-s (spray-dried WPH sample) and WPHP-f (freeze-dried sample) were assessed. These samples were quite stable under acidic conditions, remaining approximately 90% of its original reducing power and 85% of its OH• scavenging activity. However, they were susceptible to alkaline treatments (at pH>10.0) and lost>50% of their antioxidant activities. In terms of heat processing, common pasteurization (65°C×30 min) or autoclaving sterilization (121°C×20 min) treatment did not show notably effects on the antioxidant activities of these three samples. Different drying methods (spray-drying or freeze-drying) demonstrated very slight influence on their structure and activities, as further confirmed by molecular weight distribution assay. 

Enzymolysis of walnut ( Juglans regia L.) meal protein: Ultrasonication‐assisted alkaline pretreatment impact on kinetics and thermodynamics

“…Raw walnut is rated among the top four edible nuts with high protein content of more than 15 g/100 g aside its high oil content. The byproduct obtained from walnut oil production known as walnut meal (WM) contains more than 40%, approximately 80% protein on a dry matter basis (Lai et al, ; Oliveira, Rodrigues, & Bernardo‐Gil, ). This protein can be harnessed and used in food application to help increase the utility of walnut meal.…”

Stability to thermal treatment of dipeptidyl peptidase‐IV inhibitory activity of a boarfish (Capros aper) protein hydrolysate when incorporated into tomato‐based products

“…The results reported herein are consistent with the findings of Lai et al . (2016), who showed that walnut protein hydrolysates were stable and retained their antioxidant activity following heat treatment at 65 °C × 30 min and 121 °C × 20 min. Furthermore, the bioactivity exhibited by rapeseed, tuna cooking juice and bovine casein‐derived protein hydrolysate/peptides was reported to be stable when subjected to temperatures in the range 0–100 °C (Hwang, 2010; Wu et al ., 2014; Wali et al ., 2017).…”

“…To date, information regarding the influence of routinely used industrial processing and storage conditions on the bioactivity, in particular the potential anti‐diabetic activity, of protein hydrolysates when incorporated into different food matrices is limited. The majority of the research reported to date in this area has been performed with aqueous solutions of protein hydrolysates/peptides and not with delivery vehicles containing the functional protein hydrolysate/peptide ingredient (Hwang, 2010; Wu et al ., 2014; Zhu et al ., 2014; Lai et al ., 2016; Wali et al ., 2017; Rivero‐Pino et al ., 2020).…”

Effect of multi‐frequency countercurrent ultrasound treatment on extraction optimization, functional and structural properties of protein isolates from Walnut (Juglans regiaL.) meal

“…Control of food waste (by‐product) plays a vital role in reducing the source and recovery of by‐products in the food industries (Schieber, Stintzing, & Carle, 2001). Increased production of walnut oil has resulted in high amounts of by‐product (walnut meal) containing between 40% and 80% high‐quality protein (Lai et al, 2016; Liu et al, 2020; Ros, 2010). This protein‐rich by‐product used as animal feed could be harnessed for industrial use.…”

“…Literature reiterates optimization of the interaction of process constraints using response surface methodology (RSM) aiming at determining their optimum conditions for product quality (Golly et al, 2018). There exist some published literatures on the optimization processes involving walnut meal for antioxidant protein/peptide production through alcalase, pancreatin hydrolysis, and solid‐state fermentation (Gu et al, 2015; Lai et al, 2016; Liu et al, 2020; Wang et al, 2016) or trypsin (Lai et al, 2016), separation/purification of angiotensin‐I‐converting enzyme inhibitory protein/peptide (Liu et al, 2020; Liu & Wang, 2015; Wang et al, 2016). Functional properties, by definition, are the totality of physicochemical behavior or performance of proteins in food systems along the food chain (Kempka, Horvath, Fagundes, & Prestes, 2015).…”