Flavor of fava bean (Vicia faba L.) ingredients: Effect of processing and application conditions on odor-perception and headspace volatile chemistry.

Application of plant-based sources for food, e.g. fava bean, is challenged by consumer acceptance. This study attempts to understand how ingredient processing and application conditions drive fava bean flavor. An approach was used to evaluate odor perception along with the analysis of headspace volatile compounds detected during ingredient utilization. Precisely, a protein-rich ingredient, i.e. air classified fava bean concentrate, selected for its high industrial potential, was modified by pH (2, 4, 6.4 and 11), temperature (55, 75 and 95 °C) and treatment duration (30 and 360 min). The experimental design produced 36 different modified ingredients, which were further subjected to two distinct models of beverage application (pH 4 and 7). Results showed that the "green" perception detected in the initial concentrate evolved more into "cooked" perception with ingredient processing. Application conditions drove aroma changes, ranging from a "sweet" to "rancid" perception when changed from neutral to acidic pH. Aldehydes were generated in many ingredients, as well as furanoids at pH 2, terpenoids at pH 4, alcohols at pH 6.4 and ketones at pH 11. Lipid oxidation was hypothesized as the major contributor to the aroma composition in the ingredient suspensions. Reactions involving protein, sugar and carotenoid degradation, including Maillard reaction and caramelization, also played a role in the flavor generation. Different suspension matrices at different pH during ingredient application might have influenced the release of pH-dependent volatiles. This data allows to better link the role of process conditions in the generation and release of hypothesized odor-active molecules associated with different odor sensory notes. Thus, various flavor profiles can be driven by process conditions for fava bean concentrates - making it promising for several food applications.

Two Statistical Tools for Assessing Functionality and Protein Characteristics of Different Fava Bean (Vicia faba L.) Ingredients.

Fava bean (Vicia faba L.) is a promising source of proteins that can be potentially used as nutritional and/or functional agents for industrial food applications. Fava ingredients are industrially produced, modified, and utilized for food applications. Their processing conditions influence physico-chemical protein properties that further impact ingredient functionality. To design a functionally suitable ingredient, an understanding of the interrelationships between different properties is essential. Hence, this work aimed to assess two statistical analytical tools, Pearson's correlation and Principal Component Analysis (PCA), for investigating the role of the process conditions of fava ingredients on their functional and protein properties. Fava concentrates were processed by pH (2, 4, 6.4 and 11), temperature (55, 75 and 95 ∘C) and treatment duration (30 and 360 min) into different modified ingredients. These were utilized under two application conditions (pH 4 and 7), and their foam and emulsion properties as well as their ingredient characteristics (charge, solubility, and intrinsic fluorescence) were measured. The results show that foam and emulsion properties are not correlated to each other. They are associated with different protein and non-protein attributes as fava concentrate is a multi-component matrix. Importantly, it is found that the results from the two statistical tools are not fully comparable but do complement each other. This highlights that both statistical analytical tools are equally important for a comprehensive understanding of the impact of process conditions on different properties and the interrelationships between them. Therefore, it is recommended to use Pearson's correlation and principal component analysis in future investigations of new plant-based proteins.

Fava bean (Vicia faba L.) for food applications: From seed to ingredient processing and its effect on functional properties, antinutritional factors, flavor, and color.

The food industry, along with the consumers, is interested in plant-based diet because of its health benefits and environmental sustainability. Vicia faba L. (V. faba) is a promising source of pulse proteins for the human diet and can yield potential nutritional and functional ingredients, namely, flours, concentrates, and isolates, which are relevant for industrial food applications. Different processes produce and functionalize V. faba ingredients relevant for industrial food applications, along with various alternatives within each unit operation used in their production. Processing modifies functional properties of the ingredients, which can occur by (i) changing in overall nutritional composition after processing steps and/or (ii) modifying the structure and conformation of protein and of other components present in the ingredients. Furthermore, V. faba limitations due to off-flavor, color, and antinutritional factors are influenced by ingredient production and processing that play a significant role in their consumer acceptability in foods. This review attempts to elucidate the influence of different ways of processing on the functional, sensory, and safety aspects of V. faba L. ingredients, highlighting the need for further research to better understand how the food industry could improve their utilization in the market.

Purified oleocanthal and ligstroside protect against mitochondrial dysfunction in models of early Alzheimer's disease and brain ageing.

As components of the Mediterranean diet (MedDiet) olive polyphenols may play a crucial role for the prevention of Alzheimer's disease (AD). Since mitochondrial dysfunction is involved in both, brain ageing and early AD, effects of 10 different purified phenolic secoiridoids (hydroxytyrosol, tyrosol, oleacein, oleuroside, oleuroside aglycon, oleuropein, oleocanthal, ligstroside, ligstroside aglycone and ligustaloside B) and two metabolites (the plant metabolite elenolic acid and the mammalian metabolite homovanillic acid) were tested in very low doses on mitochondrial function in SH-SY5Y-APP695 cells - a cellular model of early AD. All tested secoiridoids significantly increased basal adenosine triphosphate (ATP) levels in SY5Y-APP695 cells. Oleacein, oleuroside, oleocanthal and ligstroside showed the highest effect on ATP levels and were additionally tested on mitochondrial respiration. Only oleocanthal and ligstroside were able to enhance the capacity of respiratory chain complexes. To investigate their underlying molecular mechanisms, the expression of genes associated with mitochondrial biogenesis, respiration and antioxidative capacity (PGC-1α, SIRT1, CREB1, NRF1, TFAM, complex I, IV and V, GPx1, SOD2, CAT) were determined using qRT-PCR. Exclusively ligstroside increased mRNA expression of SIRT1, CREB1, complex I, and GPx1. Furthermore, oleocanthal but not ligstroside decreased Aß 1-40 levels in SH-SY5Y-APP695 cells. To investigate the in vivo effects of purified secoiridoids, the two most promising compounds (oleocanthal and ligstroside) were tested in a mouse model of ageing. Female NMRI mice, aged 12 months, received a diet supplemented with 50 mg/kg oleocanthal or ligstroside for 6 months (equivalent to 6.25 mg/kg b.w.). Young (3 months) and aged (18 months) mice served as controls. Ligstroside fed mice showed improved spatial working memory. Furthermore, ligstroside restored brain ATP levels in aged mice and led to a significant life extension compared to aged control animals. Our findings indicate that purified ligstroside has outstanding performance on mitochondrial bioenergetics in models of early AD and brain ageing by mechanisms that may not interfere with Aß production. Additionally, ligstroside expanded the lifespan in aged mice and enhanced cognitive function.

Correction to: Two novel methylesterases from Olea europaea contribute to the catabolism of oleoside-type secoiridoid esters.

Page 5, paragraph 3, line 14, GenBank Accession Number which should read MK234850 instead of MK23485.

Two novel methylesterases from Olea europaea contribute to the catabolism of oleoside-type secoiridoid esters.

MAIN CONCLUSION: Two newly identified phytohormone cleaving esterases from Olea europaea are responsible for the glucosidase-initiated activation of the specialized metabolites ligstroside and oleuropein. Biosynthetic routes leading to the formation of plant natural products are tightly orchestrated enzymatic sequences usually involving numerous specialized catalysts. After their accumulation in plant cells and tissues, otherwise non-reactive compounds can be enzymatically activated, e.g., in response to environmental threats, like pathogen attack. In olive (Olea europaea), secoiridoid-derived phenolics, such as oleuropein or ligstroside, can be converted by glucosidases and as yet unidentified esterases to oleoside aldehydes. These are not only involved in pathogen defense, but also bear considerable promise as pharmaceuticals or neutraceuticals. Making use of the available olive genomic data, we have identified four novel methylesterases that showed significant homology to the polyneuridine aldehyde esterase (PNAE) from Rauvolfia serpentina, an enzyme acting on a distantly related metabolite group (monoterpenoid indole alkaloids, MIAs) also featuring a secoiridoid structural component. The four olive enzymes belong to the α/ß-hydrolase fold family and showed variable in vitro activity against methyl esters of selected plant hormones, namely jasmonic acid (MeJA), indole acetic acid (MeIAA), as well as salicylic acid (MeSA). None of the identified catalysts were directly active against the olive metabolites oleuropein, ligstroside, or oleoside 11-methyl ester. When employed in a sequential reaction with an appropriate glucosidase, however, two were capable of hydrolyzing these specialized compounds yielding reactive dialdehydes. This suggests that the esterases play a pivotal role in the activation of the olive secoiridoid polyphenols. Finally, we show that several of the investigated methylesterases exhibit a concomitant in vitro transesterification capacity-a novel feature, yielding ethyl esters of jasmonic acid (JA) or indole-3-acetic acid (IAA).

Effects of Long-Term Treatment with a Blend of Highly Purified Olive Secoiridoids on Cognition and Brain ATP Levels in Aged NMRI Mice.

Aging represents a major risk factor for developing neurodegenerative diseases such as Alzheimer's disease (AD). As components of the Mediterranean diet, olive polyphenols may play a crucial role in the prevention of AD. Since mitochondrial dysfunction acts as a final pathway in both brain aging and AD, respectively, the effects of a mixture of highly purified olive secoiridoids were tested on cognition and ATP levels in a commonly used mouse model for brain aging. Over 6 months, female NMRI mice (12 months of age) were fed with a blend containing highly purified olive secoiridoids (POS) including oleuropein, hydroxytyrosol and oleurosid standardized for 50 mg oleuropein/kg diet (equivalent to 13.75 mg POS/kg b.w.) or the study diet without POS as control. Mice aged 3 months served as young controls. Behavioral tests showed deficits in cognition in aged mice. Levels of ATP and mRNA levels of NADH-reductase, cytochrome-c-oxidase, and citrate synthase were significantly reduced in the brains of aged mice indicating mitochondrial dysfunction. Moreover, gene expression of Sirt1, CREB, Gap43, and GPx-1 was significantly reduced in the brain tissue of aged mice. POS-fed mice showed improved spatial working memory. Furthermore, POS restored brain ATP levels in aged mice which were significantly increased. Our results show that a diet rich in purified olive polyphenols has positive long-term effects on cognition and energy metabolism in the brain of aged mice.

Activated transglutaminase from Streptomyces mobaraensis is processed by a tripeptidyl aminopeptidase in the final step.

Transglutaminase (TGase) from Streptomyces mobaraensis is secreted as a precursor protein which is completely activated by the endoprotease TAMEP, a member of the M4 protease family [Zotzel, J., Keller, P. & Fuchsbauer, H.-L. (2003) Eur. J. Biochem. 270, 3214-3222]. In contrast with the mature enzyme, TAMEP-activated TGase exhibits an additional N-terminal tetrapeptide (Phe-Arg-Ala-Pro) suggesting truncation, at least, by a second protease. We have now isolated from the culture broth of submerged colonies a tripeptidyl aminopeptidase (SM-TAP) that is able to remove the remaining tetrapeptide. The 53-kDa peptidase was purified by ion-exchange and phenyl-Sepharose chromatography and subsequently characterized. Its proteolytic activity was highest against chromophoric tripeptides at pH 7 in the presence of 2 mm CaCl2. EDTA and EGTA (10 mm) both diminished the proteolytic activity by half. Complete inhibition was only achieved with 1 mm phenylmethanesulfonyl fluoride, suggesting that SM-TAP is a serine protease. Alignment of the N-terminal sequence confirmed its close relation to the Streptomyces TAPs. That removal of Phe-Arg-Ala-Pro from TAMEP-activated TGase by SM-TAP occurs in a single step was confirmed by experiments using various TGase fragments and synthetic peptides. SM-TAP was also capable of generating the mature N-terminus by cleavage of RAP-TGase. However, AP-TGase remained unchanged. As SM-TAP activity against chromophoric amino acids such as Pro-pNA or Phe-pNA could not be detected, the tetrapeptide of TAMEP-activated TGase must be removed without formation of an intermediate.