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The nitrogen fraction of 39 food waste streams was characterized by Kjeldahl analysis, amino acid analysis, protein analysis and racemization degree, for assessing their potential for further valorization. For every waste streams the specific nitrogen-to-protein conversion factor was calculated, allowing to assess the accurate protein content. The results indicated which streams are most rich in relevant proteins (all wastes of dairy origin, beer yeast, malted barley germs, brewing cake, rapeseed press cake, sea buckthorn spent pulp, leek leaves, parsley waste, pumpkin kernel cake, and mushroom waste), which ones have valuable proteins, but in too little amount, and also which ones are rich in proteins, but of low nutritional value. Specific data also indicated, for every waste stream, its possible use for supplementing specific amino acids. To date, this represents the most complete characterization with homogeneous methodologies of the nitrogen fraction in food waste streams ever reported in the literature and outlines in unprecedented molecular details the potentialities and the limitations of many waste streams to be used as source of proteins., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Proteolysis is the most important event occurring during maturation of dry-cured hams: it strongly influences the flavour and the texture of the aged ham by the accumulation of peptides and free amino acids released by protein hydrolysis. Apart from compounds of proteolytic origin, it has been demonstrated that also non-proteolytic amino acyl derivatives (γ-glutamyl amino acids, pyroglutamyl-amino acids and lactoyl-amino acids) may accumulate during ripening of cheese, and they can be also found in fermented soy sauce, where they contribute to the umami taste of the products. Using a semi-quantitative analysis, in this paper we report the occurrence of significant amounts of γ-glutamyl amino acids and, for the first time, pyroglutamyl-amino acids and lactoyl-amino acids, in aged ham. The amino acid counterparts were mainly found to be hydrophobic amino acids. The amount of these compounds was found to increase with time, because they are not degraded by proteolytic activity. They were also found to be stable to simulated gastrointestinal digestion. Angiotensin Converting Enzyme inhibitory activity was also tested, but they were not found to be characterized by significant ACE-inhibitory activity., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In this work the antioxidant capacity of water soluble extracts of Parmigiano-Reggiano cheese (Water Soluble Extracts - WSEs) at different aging time was studied, by measuring their radical scavenging capacity with a standard ABTS assay. The WSEs were also fractionated by semi-preparative HPLC-UV and for each fraction the antioxidant capacity and the molecular composition was determined by LC/ESI-MS, in order to identify the most active antioxidant compounds. The antioxidant capacity was also determined after simulated in vitro gastrointestinal digestion of WSEs. The data indicated that antioxidant capacity in WSE from Parmigiano-Reggiano cheese, quite unaffected by ripening time and gastrointestinal digestion, is mostly due to free amino acids, mainly tyrosine, methionine and tryptophan, and only in minimal part to antioxidant peptides.

Cheese ripening involves a complex series of biochemical events that contribute to the development of each cheese characteristic taste, aroma and texture. Proteolysis, which has been the subject of active research in the last decade, is the most complex of these biochemical events. However, also aminoacyl derivates of non-proteolytic origin (γ-glutamyl-amino acids and lactoyl-amino acids) with interesting sensory properties have been identified in cheeses. In the present work, an enzymatic activity producing γ-glutamyl-phenylalanine in Parmigiano-Reggiano water soluble extracts was observed. It was hypothesized that γ-glutamyl-amino acids and lactoyl-amino acids could be originated by enzymes of bacterial origin. In order to confirm this hypothesis, Lactobacillus helveticus and Lactobacillus rhamnosus were chosen as representative of starter and non starter microbiota of Parmigiano Reggiano cheese. They were used as model bacteria, in the presence of suitable precursors, to verify their ability to produce γ-glutamyl-phenylalanine and lactoyl-phenylalanine. The eventual abilities of these strains were tested both during growth and after cell lyses. While γ-glutamyl-phenylalanine was produced only by lysed cells, lactoyl-phenylalanine was produced either by growing or lysed cells in different amount depending on the species, the cells condition and the time of incubation., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The effect of the dry-curing processing time on the release of oligopeptides and amino acids was evaluated with 158 Parma hams subdivided into three groups: (1) traditional processing (450 days); (2) extended processing (570 days); and (3) extended aging (690 days). Most of the oligopeptides and free amino acids detected increased up to the last deadline (690 days); a sharp increase of peptides below 400 Da was the main change in most aged hams. In particular, gamma-glutamyl dipeptides showed a remarkable increase during ham extended aging, acting like permanent taste-active compounds, being unsuitable for further enzymatic breakdown. The pH of fresh hams showed negative relationships (P < 0.001) with most peptides. With regard to free amino acids, the pattern was modified by different processing lengths, together with their taste categories, so that the amino acids having monosodium glutamate-like and bitter tastes were enhanced in more aged hams.

Two selectors based on modified cyclodextrins containing a metal binding site and a dansyl fluorophore-6-deoxy-6-N-(N(alpha)-[(5-dimethylamino-1-naphthalenesulfonyl)aminoethyl]phenylalanylamino-beta-cyclodextrin-containing D-Phe (3) and L-Phe (4) moieties were synthesized. The conformations of the two selectors were studied by circular dichroism, two-dimensional NMR spectroscopy and time-resolved fluorescence spectroscopy. Cyclodextrin 4 was found to have a predominant conformation in which the dansyl group is self-included in the cyclodextrin cavity, while 3 showed a larger proportion of the conformation with the dansyl group outside the cavity. As a consequence, the two cyclodextrins were found to bind copper(II) with different affinities, as revealed by fluorescence quenching in competitive binding measurements. Addition of D- or L-amino acids induced increases in fluorescence intensity, which were dependent on the amino acid used and in some cases on its absolute configuration. The cyclodextrin 4 was found to be more enantioselective than 3, suggesting that the self-inclusion in the cyclodextrin cavity strongly increases the chiral discrimination ability of the copper(II) complex. Accordingly, a linear fluorescent ligand N(alpha)-[(5-dimethylamino-1-naphthalenesulfonyl)aminoethyl]-N(1)-propyl-phenylalaninamide, which has the same binding site and absolute configuration as 4, showed very low chiral discrimination ability. The enantioselectivity in fluorescence response was found to be due to the formation of diastereomeric ternary complexes, which were detected by ESI-MS and by circular dichroism. Time-resolved fluorescence studies showed that the fluorescence of the dansyl group was completely quenched in the ternary complexes formed, and that the residual fluorescence was due to uncomplexed ligand.

Microalgae are considered a valuable source of proteins that are used to enhance the nutritional value of foods. In this study, a standard vegetable cream recipe was reformulated through the addition of single-cell ingredients from Arthrospira platensis (spirulina), Chlorella vulgaris, Tetraselmis chui, or Nannochloropsis oceanica at two levels of addition (1.5% and 3.0%). The impact of microalgae species and an addition level on the amino acid profile and protein in vitro digestibility of the vegetable creams was investigated. The addition of microalgae to vegetable creams improved the protein content and the amino acid nutritional profile of vegetable creams, whereas no significant differences were observed in protein digestibility, regardless of the species and level of addition, indicating a similar degree of protein digestibility in microalgae species despite differences in their protein content and amino acid profile. This study indicates that the incorporation of microalgae is a feasible strategy to increase the protein content and nutritional quality of foods. [ABSTRACT FROM AUTHOR]

Peptides and amino acids generated during cocoa bean fermentation are known to be the most important precursors for the development of cocoa aroma. Although cocoa fermentation and aroma development have been extensively studied, the cocoa oligopeptide fraction is under-investigated. In particular, the identification of specific peptide sequences and the quantification of cocoa peptides are scarce in the literature. The aim of this study was to investigate the presence of oligopeptides in fermented cocoa beans. Peptides were analysed by reversed phase LC/ESI-MS and LC/ESI-MS/MS, and the molecular masses of 44 different peptides were obtained by analysing the mass spectra associated with the most intense chromatographic peaks. Peptides were identified based on the exact molecular masses, mass fragmentation patterns and by comparison with vicilin and 21 kDa cocoa seed protein sequences. Semi-quantitative data on peptide presence in fermented cocoa samples of different geographic origin, different fermentation levels and on roasted products were also provided. [ABSTRACT FROM AUTHOR]

Gamma-glutamyl-amino acids, lactoyl-amino acids and pyroglutamyl-amino acids, collectively named Non-Proteolytic Aminoacyl Derivatives (NPADs) are unusual aminoacyl derivatives of non-proteolytic origins found in consistent amount in several cheeses. Although their enzymatic origin arising from lactic acid bacteria has been demonstrated, the exact enzymes originating them, the ones eventually degrading them and also their resistance to digestive enzymes in the human gastrointestinal tract and in the blood serum after eventual absorption are still unknown. In this paper, pure enzymes and biological media were tested on NPAD and their aminoacidic precursors, for identifying the conditions favoring bioproduction and biodegradation of these compounds. Pure gamma-glutamyl-phenylalanine and its precursor (glutamic acid and phenylalanine), also in the isotopically labeled forms, were tested with Parmigiano-Reggiano extracts, blood serum and different pure enzymes, including typical digestion enzymes (pepsin, trypsin and chymotrypsin), gamma-glutamyl transpeptidase and carboxypeptidase. The data suggested that their production in cheese, and also their partial degradation, might be due to the action of peptidases and gamma-glutamyl transpeptidase. Anyway, under simulated gastrointestinal digestion and in blood serum these compounds turned out to be perfectly stable, suggesting a potential to be absorbed as such and possibly being transported to the body tissues. [ABSTRACT FROM AUTHOR]

PNA probes for the specific detection of DNA from olive oil samples by microarray technology were developed. The presence of as low as 5% refined hazelnut ( ) oil in extra-virgin olive oil ( L.) could be detected by using a PNA microarray. A set of two single nucleotide polymorphisms (SNPs) from the Actin gene of Olive was chosen as a model for evaluating the ability of PNA probes for discriminating olive cultivars. Both unmodified and C2-modified PNAs bearing an arginine side-chain were used, the latter showing higher sequence specificity. DNA extracted from leaves of three different cultivars (Ogliarola leccese, Canino and Frantoio) could be easily discriminated using a microarray with unmodified PNA probes, whereas discrimination of DNA from oil samples was more challenging, and could be obtained only by using chiral PNA probes. [ABSTRACT FROM AUTHOR]

Abstract: For the first time, the identification of N-γ-glutamyl-, N-pyroglutamyl- and N-lactoyl-amino acids in Parmigiano-Reggiano cheese is reported. Their structures were assigned by electrospray mass spectrometric analysis and demonstrated for several compounds by the synthesis of authentic specimens and sample spiking. The comparison with the synthesised compounds also allowed the determination of their absolute stereochemistry (l,l), which indicated a common enzymatic origin. All these molecules were shown to accumulate in Parmigiano-Reggiano during ripening, probably because of a resistance to proteolysis due to their unusual structures. Thus, these compounds can be used as markers of ripening time and may be involved in the development of the pleasant flavour of aged cheeses. Their presence in other cheeses was also demonstrated. [Copyright &y& Elsevier]

Abstract: A new submonomeric approach for the Fmoc solid phase synthesis of chiral PNAs is reported here. The design and synthesis of a new d-lysine-based Fmoc submonomer obtained by replacing the nucleobase residue with an Alloc group, compatible with Fmoc chemistry, is described starting from d-lysine and Fmoc-aminoacetaldehyde. The desired submonomer was obtained in high yield with no racemization. The conditions for synthesizing a chiral PNA dimer on solid support by a submonomeric approach have been optimized, allowing to obtain the desired PNA with a very high optical purity. [Copyright &y& Elsevier]

Abstract: The synthesis of new chiral PNA analogues based on lysine is reported. In particular, l- and/or d-lysine-based PNA submonomers bearing two lysine side chains exactly spaced as in the dipeptide Lys-Lys were synthesized and incorporated in the middle of decameric PNA strands, obtaining four diastereomeric (LD, DL, LL and DD) lysine-based chiral PNAs. The hybridization with their complementary antiparallel DNA strand was studied by melting temperature determination and compared with the analogue achiral PNA and chiral PNAs bearing one residue with either of the two lysine enantiomers. The binding abilities were shown to be strongly dependent on the configuration of the stereogenic centres. [Copyright &y& Elsevier]

Insects are becoming increasingly relevant as protein sources in food and feed. The Black Soldier Fly (BSF) is one of the most utilized, thanks to its ability to live on many leftovers. Vegetable processing industries produce huge amounts of by-products, and it is important to efficiently rear BSF on different substrates to assure an economical advantage in bioconversion and to overcome the seasonality of some leftovers. This work evaluated how different substrates affect the protein and amino acid content of BSF. BSF prepupae reared on different substrates showed total protein content varying between 35% and 49% on dry matter. Significant lower protein contents were detected in BSF grown on fruit by-products, while higher contents were observed when autumnal leftovers were employed. BSF protein content was mainly correlated to fibre and protein content in the diet. Among amino acids, lysine, valine and leucine were most affected by the diet. Essential amino acids satisfied the Food and Agricultural Organization (FAO) requirements for human nutrition, except for lysine in few cases. BSF could be a flexible tool to bio-convert a wide range of vegetable by-products of different seasonality in a high-quality protein-rich biomass, even if significant differences in the protein fraction were observed according to the rearing substrate. [ABSTRACT FROM AUTHOR]

Brine soaking is one of the most important steps in the production of Parmigiano Reggiano cheese, since it determines the amount of salt in the final product. Reduction in salt in Parmigiano Reggiano cheese might be important for improving its nutritional profile, but it could affect the manufacturing processes by altering proteolysis and consequently the product quality. In this study, for the first time, salt reduction was explored at the industrial level on real cheese samples manufactured in a local dairy. In particular, 20 wheels were produced with conventional (18 days, 10 wheels) and shorter (12 days, 10 wheels) brining steps. In every group, wheels were studied at two different ripening times, 15 and 30 months. A shorter brining time resulted in an average 12% decrease in salt content. A full characterization of free amino acids and peptides was performed by LC-MS on all samples. Free amino acids and peptides, as expected, increased with ripening, due to proteolysis, with samples having low salt content showing a slightly faster increase when compared to standard ones, hinting to a slightly accelerated proteolytic process. Nonetheless, low-salt and conventional cheeses shared similar sensory profiles at both ripening times. [ABSTRACT FROM AUTHOR]

Parmigiano–Reggiano (PR) is a worldwide known Italian, long ripened, hard cheese. Its inclusion in the list of cheeses bearing the protected designation of origin (PDO, EU regulation 510/2006) poses restrictions to its geographic area of production and its technological characteristics. To innovate the Parmigiano–Reggiano (PR) cheese manufacturing chain from the health and nutritional point of view, the output of defatted PR is addressed. Two defatting procedures (Soxhlet, and supercritical CO2 extraction) were tested, and the obtained products were compared in the composition of their nitrogen fraction, responsible for their nutritional, organoleptic, and bioactive functions. Free amino acids were quantified, and other nitrogen compounds (peptides, proteins, and non-proteolytic aminoacyl derivatives) were identified in the extracts and the mixtures obtained after simulated gastrointestinal digestion. Moreover, antioxidant and angiotensin converting enzyme (ACE) inhibition capacities of the digests were tested. Results obtained from the molecular and biofunctional characterization of the nitrogen fraction, show that both the defatted products keep the same nutritional properties of the whole cheese. [ABSTRACT FROM AUTHOR]

The extent of protein enzymatic hydrolysis is considered to be mostly determined by protease specificity and the number of cleavage sites (CS) on the substrate. However, this theoretical maximum is typically not reached. The limited hydrolysis of certain CS may be due to the differences in enzyme preference resulting from neighbouring amino acids (AA) of the CS (secondary specificity). This study aims to find the link between enzyme secondary specificity and the relative hydrolysis rate constants (selectivity) of individual CS in a protein, to better predict the maximum experimental degree of hydrolysis. Bovine tryptic hydrolysis of α-lactalbumin and β-casein showed that ≥50% of the CS were inefficiently hydrolysed. The selectivity depended on the number of charged AA at P2 and P2′ positions of a CS. Trypsin efficiently cleaves CS with neutral AA at these two positions. The selectivity towards 12 out of 18 (67%) CS in β-lactoglobulin was correctly predicted. The predicted maximum degree of hydrolysis is within ∼13% error of the experimental value, which is ∼5 times better than the prediction based only on enzyme specificity. This work helps to estimate the extent of hydrolysis and the peptide formation of bovine tryptic hydrolysis of other substrates. [ABSTRACT FROM AUTHOR]

[Display omitted] • The essential amino acids profile is comparable for both analogue and beef burgers. • Protein integrity of plant- and animal-based products was not affected by treatments. • INFOGEST in vitro model showed good protein solubilisation for both protein sources. • High prevalence of collagen-deriving peptides was observed in beef digestates. • The quality of raw material affects digestibility regardless of the protein source. Nowadays, consumers are increasingly inclined toward plant-based meat analogues for sake of food security, safety, and sustainability. This growing interest, not only from consumers but also from food companies, brought the offer on the market to be wide and vast. From our previous study it emerged that the market supply, especially the Italian one, is diversified both in terms of protein sources and nutrient content. Although these products are increasingly consumed, for most of the meat analogues today on the market, little is still known about their actual protein quality and digestibility. To fill this gap, in this study different commercial plant-based burgers (2 soy-based and 2 pea-based) were selected and compared to two beef burgers, as controls, in terms of protein quality and digestibility. The findings of this study demonstrated the essential amino acidic profile lacks lysine for almost all burgers (including the meat-based ones) compared to the amino acid scoring pattern set by FAO/WHO (for older children and adults), even if the sum of essential amino acids was within the range of sufficiency. All samples showed good initial protein integrity with low hydrolysis (above 6%) and percentage of D-enantiomers (above 15%). The study of the digestibility, performed by the validated INFOGEST in vitro model, showed better protein solubilisation in the case of meat burgers (63 ± 3% and 61 ± 8%), but a good digestibility also in the case of plant-based ones (from 55% to 40%). The degree of hydrolysis of the solubilised proteins was very high in all samples (from 65% to 40%) indicating a very good protein accessibility to digestive enzymes. The analysis of the peptide fraction of digestates indicated a high prevalence of collagen proteins in beef burgers and of reserve proteins in plant-based burgers. This study showed that the differences between these products are mostly dependent on the quality of the raw materials used, rather than on the vegetal or animal protein source. Therefore, to have a product with a good protein quality and digestibility, independently from the protein origin, the consumer needs to make an accurate choice, carefully reading the ingredient list. [ABSTRACT FROM AUTHOR]

Peptides and amino acids generated during cocoa bean fermentation are the most important precursors for the development of cocoa aroma, however cocoa oligopeptide fraction is under-investigated. In this study, we perform a deep investigation of the presence of oligopeptides in unfermented, under fermented, and well-fermented cocoa beans from all of the main producing countries, with the aim to obtain a better definition of cocoa quality and a deeper comprehension of biochemical changes occurring during fermentation. Oligopeptides were determined by UPLC/ESI-MS and 35 low-molecular weight peptides were identified and subjected to semi-quantitative analysis. Results showed that fermented cocoas can be differentiated from unfermented cocoas by their possession of a higher total amount of oligopeptides and a lower ratio of vicilin to 21 kDa cocoa seed albumin peptides. A variability in the peptide pattern was observed also among well-fermented cocoa samples of different geographical origin, suggesting diversified proteolytic activities. [ABSTRACT FROM AUTHOR]