Sequence alterations affect the antidiabetic attributes of hazelnut peptide fractions during the industrial manufacture and simulated digestion of hazelnut paste.

Press cakes are by-products of cold press oil manufacture and are characterized by significant protein concentrations. Our group has previously demonstrated potential bioactive attributes of hazelnut protein hydrolysates including their antidiabetic activities. Here, an effort was made to utilize DPP-IV (Dipeptidyl peptidase-IV)-inhibitory hazelnut peptides in industrial food manufacture. Hazelnut protein isolates (approx. 95% protein) were obtained via an alkali extraction-isoelectric precipitation method. Papain, bromelain and pepsin were used in the enzymatic hydrolysis and hydrolysates were fractionated via Fast Protein Liquid Chromatography. As a general observation, although fractionation lead to dilution of the samples, fractions were observed to be more bioactive than the total hydrolysates. In vitro antidiabetic activities of the fractions were tested and 3 antidiabetic fractions were added to hazelnut paste. Afterwards simulated gastrointestinal digestion and antidiabetic activity assays were performed. DPP-IV inhibition was the major antidiabetic mechanism in the fractions and digested paste, while some fractions were characterized by comparable IC50 values as the positive controls. Alpha-glucosidase inhibition was limited by digestion trials, whereas alpha-amylase inhibition was only slight in the digested paste (< %6). In silico analyses predicted partial degradation of the peptides, whereas the interactions between DPP-IV or alpha-glucosidase and hazelnut peptides were predicted to be significant (p < 0.05). Consequently hazelnut press cakes were regarded as a potential source of antidiabetic peptides that can be used in industrial manufacture of functional foods, while food processing conditions or gastrointestinal digestion could largely affect peptide bioactivity. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05601-2.

Hazelnut peptide fractions preserve their bioactivities beyond industrial manufacture and simulated digestion of hazelnut cocoa cream.

Cold press hazelnut cakes represent a concentrated source of proteins that can be industrially exploited. Previously, bioactive attributes of hazelnut protein hydrolysates including antihypertensive and antidiabetic activities were documented. Here, we made an attempt to utilize bioactive hazelnut protein hydrolysates (1 % w/w) in the manufacture of industrial hazelnut cocoa cream and investigate their stability through processing and simulated gastrointestinal digestion. The inclusion of bioactive peptide fractions was a safe practice in the microbiological sense. Proteolysis lowered the potential allergenicity of hazelnut proteins in the cocoa cream products up to about 20 %. In silico trypsinolysis predicted partial degradation for 51.8 % of the peptide sequences (i.e., 43/83) that were present in the hydrolysates. However, partial degradation and mixing of degraded vs non-degraded peptides preserved and/or further elevated bioactive attributes in the digested cocoa cream products in terms of Angiotensin converting enzyme (ACE)-inhibitory (up to about 92 %) and antidiabetic activities (between 7.5 and 44.4 %). In most cases, however, antioxidative activity was < 10 %. While simulated in vitro digestion potentially influenced the bioactive attributes of protein hydrolysates, the influence of cocoa cream processing and food matrix were relatively limited for hydrolysate fractions and more pronounced for protein isolates. Hazelnut press cakes represent a significant resource for the generation and industrial utilization of bioactive peptides, which could preserve their bioactivity beyond industrial manufacture and digestion and lead to slightly reduced allergenicity.

Tombul hazelnut (Corylus avellana L.) peptides with DPP-IV inhibitory activity: In vitro and in silico studies.

Cold press technology generates high quality value-added oil products along with highly stable oilseed cakes. Hazelnut cakes are characterized by high protein concentrations that can be industrially valorized. Here, using an aqueous extraction scheme along with enzymatic proteolysis and FPLC (fast protein liquid chromatography)-based fractionation, a variety of hazelnut peptide fractions with varying bioactive properties were manufactured and their sequences were determined based on mass spectrometry. DPP-IV inhibitory attributes were determined based on an in vitro DPP-IV assay and in silico techniques were administered for for the analysis of overall bioactive potential and DPP-IV inhibitory characteristics of peptides. Based on these investigations, 256 peptides were identified in 81 different fractions. The majority of fractions were characterized with low to moderate DPP-IV inhibitory activity possibly due to their dilute nature. Some hazelnut peptides were characterized by comparable IC50 values as the positive control (Diprotin-A). The most influential 7 peptides were shown to generate higher docking scores than the control. The main interaction mechanism between hazelnut peptides and DPP-IV possibly depended on hydrophobic interactions. While further concentration could enhance the DPP-IV inhibitory potential of hazelnut peptides, hazelnut cakes represent a sustainable resource of potentially antidiabetic peptides.