Abstract
Proteins from hemp bran (HPB), a byproduct of the hemp seed food-processing chain, were chemically extracted, hydrolyzed by Alcalase, and separated by membrane ultrafiltration into four fractions (MW <1, 1–3, 3–5, and >5 kDa). The antioxidant and antihypertensive properties of the initial extract and the fractions were evaluated by in vitro assays for their ability to scavenge radical species, bind with metal ions, reduce ferric ions, and inhibit angiotensin-converting enzyme (ACE) activity. Bioactive peptides were identified by high-resolution mass spectrometry and sequence comparison with BIOPEP and BioPep DB databases. The hydrolysate was strongly antioxidant and ACE-inhibiting; the most bioactive peptides were further concentrated by ultrafiltration. Of the 239 peptides identified, 47 (12 antioxidant and 35 ACE-inhibitory) exhibited structural features correlated with the specific bioactivity. These results highlight the promise of hydrolysate and size-based HPB fractions as natural functional ingredients for the food or pharmaceutical industry.
Highlights
In the last few years, the recovery of proteins from agricultural and agro-food industry waste byproducts has garnered more attention, as improving the sustainability of the food chain has become more urgent
The first step of the process is the mechanical pressing of the seeds, which yields crude oil and small cylindrical bars of hemp meal (HPM)
The coarser fraction, representing about 10% of the seed, is normally used for animal feed or even discarded
Summary
In the last few years, the recovery of proteins from agricultural and agro-food industry waste byproducts has garnered more attention, as improving the sustainability of the food chain has become more urgent. After the mixture stood for 5 min at room temperature, it was centrifuged (14,000g, 10 min, 4 °C), and the supernatant was analyzed by the Kjeldahl assay to obtain the Alc 10% TCA-soluble nitrogen This value was used in the following equation to calculate the DH (%): DH(%) = Alc 10%TCA − soluble N·100/total N , where total N is the total nitrogen content in undigested HPBPE (g) measured by the Kjeldahl assay. Aliquots of the sample (10 μL) were blended with 300 μL of the FRAP reagent; after incubation at room temperature for 10 min, the absorbance of the mixture at 593 nm was measured. The ACE-inhibitory activity was measured using the method of Sentandreu and Toldra.[28] Aliquots of the sample (50 μL) were mixed with the ACE solution (50 μL, 15 mU/mL) and preincubated at 37 °C for 10 min. De novo peptide sequencing was carried out with the Pepnovo software (http://proteomics.ucsd.edu/ProteoSAFe/) with the following parameters: fragment mass tolerance, ±0.12 Da; peptide
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