Mystery of novel clove-like off-flavor in orange juice solved

Off-flavor in orange juice

Peer-Reviewed Publication

LEIBNIZ-INSTITUT FÜR LEBENSMITTEL-SYSTEMBIOLOGIE AN DER TU MÜNCHEN

 

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PHD STUDENT EVA BAUERSACHS IS WORKING IN THE SENSORY LAB AT THE LEIBNIZ INSTITUTE FOR FOOD SYSTEMS BIOLOGY AT THE TECHNICAL UNIVERSITY OF MUNICH

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CREDIT: PHOTO CREDIT: J. KRPELAN / LEIBNIZ-LSB@TUM

A research team led by the Leibniz Institute for Food Systems Biology at the Technical University of Munich has solved the mystery of a novel clove-like off-flavor in orange juice, the cause of which was previously unknown. The study proves for the first time that the undesirable flavor note is due to the odorant 5-vinylguaiacol. As the results of the study show, the substance is mainly produced during the pasteurization process when residues of a cleaning agent react with a natural orange juice component under the influence of heat.

This is not the first time that the orange juice industry has had to contend with clove odor. So far, 4-vinylguaiacol has been considered the main cause of this undesirable flavor note, which is particularly abundant in orange juices that have been stored for a long time. The quantitative determination of this odorant has therefore long been an established part of routine quality controls.

Eva Bauersachs, PhD student at the Leibniz Institute in Freising and first author of the study, explains: "Recently, however, we have received reports of orange juice samples that had a pronounced clove odor despite a low concentration of 4-vinylguaiacol. We therefore asked ourselves which other odorants contribute to this undesirable off-flavor."

On the trail of off-flavors

To investigate this question, the research group led by Martin Steinhaus, head of the Food Metabolome Chemistry research group at the Leibniz Institute, carried out extensive investigations in cooperation with the Professorship of Functional Phytometabolomics and the Chair of Food Chemistry and Molecular Sensory Science at the Technical University of Munich. The aim was to identify the odorants that cause the previously unexplained off-flavor and to elucidate their origins.

Using techniques such as gas chromatography-olfactometry and aroma extract dilution analysis, the team identified the odorant 5-vinylguaiacol as the source of the off-flavor in an orange juice with a pronounced clove odor. The presence of this substance in orange juice was previously unknown. Compared to 4-vinylguaiacol, it even proved to be more odor-active in five out of six commercially available orange juices with a clove-like off-flavor.

Natural component + cleaning agent residue + heat = off-flavor

Further studies suggested that 5-vinylguaiacol is formed during pasteurization when the characteristic orange juice component hesperidin reacts with peracetic acid. Peracetic acid is used as a cleaning agent for cleaning-in-place (CIP) in the fruit juice industry, among others.

"Inadequate rinsing of the machines after the CIP process could therefore have led to contamination of the orange juice with peracetic acid and caused the formation of 5-vinylguaiacol during further processing," says principal investigator Martin Steinhaus. Based on the new scientific findings, the team recommends that orange juice processing companies should no longer use peracetic acid as a cleaning agent.

Publication: Bauersachs, E., Walser, V., Reglitz, K., Dawid, C., and Steinhaus, M. (2024). Peracetic acid residues in orange juice can lead to a 5-vinylguaiacol-induced clove-like off-flavor via Baeyer-Villiger oxidation of hesperidin. Food Chemistry 440, 138252. doi.org/10.1016/j.foodchem.2023.138252.

More Information:

Other sources of off-flavors in orange juice:

4- and 5-vinylguaiacol are not the only odorants that may be the cause of off-flavors in orange juice. For example, heating orange juice can produce cabbage-like smelling dimethyl sulfide. Prolonged storage of the juice can also lead to chemical reactions that produce α-terpineol, which smells like turpentine. This odorant is formed under the influence of acid from the compounds limonene and linalool, which are present in high concentrations in orange juice. In addition, oxidation reactions during storage can lead to the formation of (S)-carvone from limonene, which smells like caraway.

Orange juice is very popular:

Orange juice is one of the world's most popular beverages. According to Statista data from 2022, the amount consumed annually was around 8.15 billion liters. The USA and Germany had the highest consumption rates, with per capita consumption of around 6.6 and 5.9 liters respectively.

Contacts:

Scientific Contact:

PD Dr. Martin Steinhaus
Speaker of Section I and Head of the Research Group Food Metabolome Chemistry
Leibniz Institute for Food Systems Biology
at the Technical University of Munich (Leibniz-LSB@TUM)
Lise-Meitner-Str. 34
85354 Freising, Germany
E-mail: m.steinhaus.leibniz-lsb(at)tum.de

Eva Bauersachs
Research Group Food Metabolome Chemistry
Phone: +49 8161 71-2722
E-mail: e.bauersachs.leibniz-lsb(at)tum.de

Press Contact at Leibniz-LSB@TUM:

Dr. Gisela Olias
Knowledge Transfer, Press and Public Relations
Phone: +49 8161 71-2980
E-mail: g.olias.leibniz-lsb(at)tum.de

www.leibniz-lsb.de

Information about the Institute:

The Leibniz Institute for Food Systems Biology at the Technical University of Munich (Leibniz-LSB@TUM) comprises a new, unique research profile at the interface of Food Chemistry & Biology, Chemosensors & Technology, and Bioinformatics & Machine Learning. As this profile has grown far beyond the previous core discipline of classical food chemistry, the institute spearheads the development of a food systems biology. Its aim is to develop new approaches for the sustainable production of sufficient quantities of food whose biologically active effector molecule profiles are geared to health and nutritional needs, but also to the sensory preferences of consumers. To do so, the institute explores the complex networks of sensorically relevant effector molecules along the entire food production chain with a focus on making their effects systemically understandable and predictable in the long term.

The Leibniz-LSB@TUM is a member of the Leibniz Association, which connects 97 independent research institutions. Their orientation ranges from the natural sciences, engineering and environmental sciences through economics, spatial and social sciences to the humanities. Leibniz Institutes devote themselves to social, economic and ecological issues. They conduct knowledge-oriented and application-oriented research, also in the overlapping Leibniz research networks, are or maintain scientific infrastructures and offer research-based services. The Leibniz Association focuses on knowledge transfer, especially with the Leibniz Research Museums. It advises and informs politics, science, business and the public. Leibniz institutions maintain close cooperation with universities - among others, in the form of the Leibniz Science Campuses, industry and other partners in Germany and abroad. They are subject to a transparent and independent review process. Due to their national significance, the federal government and the federal states jointly fund the institutes of the Leibniz Association. The Leibniz Institutes employ around 21,000 people, including almost 12,000 scientists. The entire budget of all the institutes is more than two billion euros.

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JOURNAL

Food Chemistry

DOI

10.1016/j.foodchem.2023.138252 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Peracetic acid residues in orange juice can lead to a 5-vinylguaiacol-induced clove-like off-flavor via Baeyer-Villiger oxidation of hesperidin.

 

Study demonstrates antitumor action of substance present in Brazilian green propolis

The analysis compared the effects of artepillin C on healthy cells and cancer cells, as well as the effects on its efficacy of variations in the medium’s pH.

Peer-Reviewed Publication

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO

Propolis has long been used in traditional medicine and has won attention from the scientific community following proof of its health benefits, which include antioxidant, anti-inflammatory, antimicrobial, antitumor and immunomodulatory properties. Its composition varies according to origin, geographic location, and the bee species that produces it. Researchers affiliated with São Paulo State University (UNESP) in Brazil and the University of Southern Denmark (SDU) set out to analyze Brazilian green propolis, which is produced by the Africanized honeybee (Apis mellifera).  

Its main component is artepillin C (3,5-diprenyl-4-hydroxycinnamic acid), a phenolic compound primarily found in the resin of Baccharis dracunculifolia, a native Brazilian plant (popular name alecrim-do-campo) known to have antitumor properties.

“Prior research showed that artepillin C can alter model biological membranes, thin films around living cells, especially when we vary the pH of the medium in which they are placed,” said Wallance Moreira Pazin, a professor in the Department of Physics and Meteorology at UNESP’s Bauru School of Sciences (FC).

The researchers decided to find out how healthy cells and tumor cells behaved biochemically when brought into contact with artepillin C, focusing for this purpose on fibroblasts – the primary cells in healing and maintenance of connective tissue – and glioblastoma cells respectively. Glioblastoma is the most common primary brain cancer.

The culture medium’s pH was also varied to see whether a more acid microenvironment would lead to different effects of artepillin C. “This is relevant because tumor tissue converts glucose into lactic acid and makes the extracellular microenvironment more acid,” said Pazin, first author of an article on the research published in the journal Life. 

They next performed a meticulous analysis of the effects of the propolis on cell membranes, using an optical microscope to observe the integrity, fluidity and morphology of the membranes. The analysis showed that artepillin C interacted intensely with tumor cells, altering their fluidity and potential for reorganization. It also triggered autophagy, a cleansing process that involves degradation of worn, abnormal or malfunctioning cellular components. 

The study was supported by FAPESP via four projects (16/09633-4, 17/23426-4, 18/22214-6 and 20/12129-1). According to Pazin, it contributes to a deeper understanding of the substance’s action mechanisms and provides insights for future research leading to innovative treatments for cancer.

“However, although in vitro trials have demonstrated high efficiency for this molecule’s biological activities, oral or topical administration to patients would be hindered by certain particularities, such as low absorption and bioavailability,” Pazin said. “In this context, strategies to enhance its therapeutic action will be required in order for progress to be possible in the use of artepillin C against tumors. An example would be the deployment of nanocarriers for controlled release.”  

About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

  

 

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JOURNAL

Life

DOI

10.3390/life13112186 

ARTICLE TITLE

pH-Dependence Cytotoxicity Evaluation of Artepillin C against Tumor Cells

 

Scientists reveal why blueberries are blue

Peer-Reviewed Publication

UNIVERSITY OF BRISTOL

 

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BLUEBERRIES

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CREDIT: ROX MIDDLETON

Tiny external structures in the wax coating of blueberries give them their blue colour, researchers at the University of Bristol can reveal.

This applies to lots of fruits that are the same colour including damsons, sloes and juniper berries.

In the study, published today in Science Advances, researchers show why blueberries are blue despite the dark red colour of the pigments in the fruit skin. Their blue colour is instead provided by a layer of wax that surrounds the fruit which is made up of miniature structures that scatter blue and UV light. This gives blueberries their blue appearance to humans and blue-UV to birds. The chromatic blue-UV reflectance arises from the interaction of the randomly arranged crystal structures of the epicuticular wax with light.

Rox Middleton, Research Fellow at Bristol’s School of Biological Sciences, explained: “The blue of blueberries can’t be ‘extracted’ by squishing – because it isn’t located in the pigmented juice that can be squeezed from the fruit. That was why we knew that there must be something strange about the colour.

“So we removed the wax and re-crystallised it on card and in doing so we were able to create a brand new blue-UV coating.”

The ultra-thin colorant is around two microns thick, and although less reflective, it’s visibly blue and reflects UV well, possibly paving the way for new colorant methods.

“It shows that nature has evolved to use a really neat trick, an ultrathin layer for an important colorant," added Rox.

Most plants are coated in a thin layer of wax which has multiple functions, many of which scientists still don’t understand. They know that it can be very effective as a hydrophobic, self-cleaning coating, but it's only now they realise how important the structure is for visible coloration.

Now the team plan to look at easier ways of recreating the coating and applying it. This could lead to a more sustainable, biocompatible and even edible UV and blue-reflective paint.

Furthermore these coatings could have the same multiple functions as natural biological ones that protect plants.

Rox added: “It was really interesting to find that there was an unknown coloration mechanism right under our noses, on popular fruits that we grow and eat all the time.

“It was even more exciting to be able to reproduce that colour by harvesting the wax to make a new blue coating that no-one’s seen before.

“Building all that functionality of this natural wax into artificially engineered materials is the dream!”

 

Diagram showing how wax structure reflect light

CREDIT

Rox Middleton

Paper:

‘Self-assembled, Disordered Structural Colour from Fruit Wax Bloom’ by Rox Middleton et al in Science Advances.

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JOURNAL

Science Advances

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Self-assembled, Disordered Structural Colour from Fruit Wax Bloom

ARTICLE PUBLICATION DATE

7-Feb-2024

 

Friend or foe? MSU researchers explore ancient partnership between moss and fungi

Study could have impact on food supply and future space exploration

Peer-Reviewed Publication

MICHIGAN STATE UNIVERSITY

 

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A MUSHROOM COEXISTING WITH ITS MOSSY NEIGHBOR. AT LEAST 80% OF MODERN PLANTS COORDINATE WITH FUNGI, WITH THESE RELATIONSHIPS HELPING PLANTS GROW STRONGER AND BECOME MORE RESILIENT.

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CREDIT: BRITTA HAMBERGER

The next time you walk through the woods in the dead of winter, take a moment to see if you can spot one of nature’s most persistent and heartiest survivors.

No, not the patch of brown grasses peeking through a snowbank, or the acres of trees with their bare boughs and branches, waiting for spring.

Look down, and you’ll find the only green to see is right under your boot — a lush carpet of mosses.

For Björn Hamberger, a James K. Billman Jr., M.D., Endowed Professor in the College of Natural Science’s Department of Biochemistry and Molecular Biology, this year-round toughness is cause for admiration on its own.

“It gives you an idea of just how resilient these organisms are, and it’s probably one of the reasons that mosses have stuck around and haven’t been lost through evolution,” said Hamberger.

But it’s also a starting point for research with a scope that spans eons — from ancient Earth to humanity’s future in space. Appearing in The Plant Journal, the Hamberger lab’s latest paper seeks to better understand how mosses and other plants conquered our planet, and how, in order to do so, may have gotten some much-needed help from their longtime collaborators fungi.

From early Earth to future Mars

Mosses made the transition to land 450 million years ago during the Ordovician period, a process that Hamberger suspects couldn’t have succeeded without some teamwork. 

When mosses made landfall, they would’ve had to account for a host of new and challenging variables, including water regulation, gravity, fluctuating temperatures and exposure to UV light.

Thankfully, mosses encountered a landscape already colonized by early fungi whose root-like networks, or mycelium, could absorb critical nutrients from the earth. In exchange for these nutrients, early terrestrial plants provided the fungi with a carbon source, kickstarting a new relationship that’s endured until the current day.

“At least 80% of modern plants still collaborate in some way with fungi, getting help to grow stronger and to become more resilient,” Hamberger explained. “As we look into a future where plants need to sustain a growing population, this will be a critical factor.”

Working with mosses for over a decade, Hamberger and his research group took part in a special exhibit at the Detroit Science Gallery called “Fog of Dawn” in 2019 that featured mosses growing in terrariums aimed at mimicking the ambience of primordial Earth and the subsequent takeover of plants and fungi.

The group also engineered moss to express foreign, modern land-plant biochemical pathways, producing products such as patchouli oil.

Here, Hamberger sees exciting potential in the realm of space exploration. Mosses and other plants could act as natural fabricators for building materials or medicines while converting carbon dioxide to oxygen during space flights.

“If you can bring plants with you on such a journey and give them the blueprints to create useful products, that will cut down on the immense weight of raw materials in orbit,” Hamberger said.

“Plus, when it comes to terraforming a place such as Mars, why not start with moss — a plant that’s successfully altered our own planet already?”

With their latest research in The Plant Journal, the Hamberger lab hopes to further pull back the curtain on plant-microbial interactions and discover the ways moss and fungi communicate at a microscopic level.

Friend or foe?

To accomplish these goals, Hamberger and Davis Mathieu, a doctoral student and first author of the paper, designed an experiment that would provide a front row seat to moss-fungi interactions in real-time.

Over three months, the lab observed the moss, Phsycomitrium patens, colonize different terrariums. Some habitats were entirely without fungi, while others were cocultured with two species of the ground-dwelling fungi lineage, Mortirellaceae, which likely existed at the same time plants first began to conquer land.

The fungi were provided by fungal and genetics expert Greg Bonito, associate professor in MSU’s Department of Plant, Soil and Microbial Sciences and a long-time collaborator of Hamberger.

Using microscopy, genetic analysis and Raspberry Pi microcomputers, the researchers tracked the subtle but distinct ways the moss interacted with its fungal neighbors. The team discovered that these interactions came to depend on a unique addition to the cast — endobacteria within the fungi.

These endobacteria provided a challenging question of their own. The endobacteria are completely dependent on their fungal host for survival, but it was unclear if they were bringing any value to the relationship.

“Generally, endobacteria are not seen as beneficial to fungi, with cells experiencing some big trade-offs for housing them,” said Mathieu. “This of course raises the question: why are they still around?”

Mathieu and others found that when endobacteria are present, fungi can more easily interact with their mossy neighbors. When experimenting with fungi that have their endobacteria removed, a complex web of relationships began to appear.

For instance, one species of fungi seemed to “eat” the moss from the inside when its endobacteria were present. But in samples where the endobacteria were absent?

“It lives side-by-side with the moss, totally indifferent,” Mathieu explained.

Meanwhile, another species of fungi that provided benefits to the moss changed its behavior when its endobacteria were removed. The fungi started producing spore-like structures indicative of stress and no longer colonized the moss as they once did.

The Hamberger lab is looking forward to further unraveling these friend-or-foe relationships between moss, fungi and endobacteria, and what these discoveries mean for understanding life on Earth.

“We thought we’d start with something simple and straightforward — the beginning of land plant life,” Hamberger said ironically. “But it turns out there’s this super exciting and very complex story that can teach us something about what happened during land plant evolution, what got us on this planet and what might get us to a different planet.”

He also hopes that this research might spur interest in crucial lifeforms we pass by every day, often without realizing it.

“Maybe it might inspire a little bit of appreciation for these cool organisms who can live under harsh conditions and are the first ones in spring to say, ‘Yay, let’s go,’ when the snow melts and the sunlight returns.”

Four panels of microscopic analysis show long, tube-like moss cells that have been colonized by smaller, filament-like fungal structures. White arrows are superimposed on the images, pointing to specific interactions.

Michigan State University researchers discovered a complex set of relationships dependent on the presence of endobacteria within the fungi themselves.

CREDIT

Mathieu, D., Bryson, A.E., Hamberger, B., Singan, V., Keymanesh, K., Wang, M., Barry, K., Mondo, S., Pangilinan, J., Koriabine, M., Grigoriev, I.V., Bonito, G. and Hamberger, B. (2024), Multilevel analysis between Physcomitrium patens and Mortierellaceae endophytes explores potential long-standing interaction among land plants and fungi. Plant J. https://doi.org/10.1111/tpj.16605

A close-up of moss on the forest floor during the Michigan winter. The latest research from the Hamberger lab at Michigan State University explores the long-running relationship between moss and fungi, and how this relationship is impacted by endobacteria.

CREDIT

Britta Hamberger

Björn Hamberger (left) and Davis Mathieu (right) pose next to a terrarium containing moss and fog. The Hamberger lab at Michigan State University has studied mosses for over a decade. This research considers how moss and other plants successfully transformed our planet, and how these organisms can help us tackle complex future problems, from food supply to space exploration.

CREDIT

Courtesy of Björn Hamberger

JOURNAL

The Plant Journal

DOI

10.1111/tpj.16605 

ARTICLE TITLE

Multilevel analysis between Physcomitrium patens and Mortierellaceae endophytes explores potential long-standing interaction among land plants and fungi

 

Exceptionally rapid tooth development and ontogenetic changes in the feeding apparatus of the Komodo dragon

Toothy Dragon: Shed teeth, histology and X-ray CT reveal exceptionally rapid tooth development in the largest living lizard

Peer-Reviewed Publication

UNIVERSITY OF TORONTO

 

IMAGE: 

KILAT, 20-YEAR-OLD KOMODO DRAGON.

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CREDIT: TORONTO ZOO

Tea Maho and Robert R. Reisz
University of Toronto Mississauga

 

Kilat, the largest living lizard at the Toronto Metro Zoo, like other members of his species (Varanus komodoensis), truly deserves to be called the Komodo Dragon! Its impressive size and the way it looks at you and tracks your every move makes you realize that it is an apex predator, not unlike a ferocious theropod dinosaur. So, it is not surprising when you look around at his enclosure to find that there are shed teeth sparkling on the ground, a common find when hunting for Mesozoic theropod dinosaurs. This startling phenomenon led us to study the teeth and feeding behaviour of this fascinating predator. The Toronto Zoo Team generously collected many shed teeth and allowed us to undertake this study, and skulls in the skeletal collection of the Royal Ontario Museum were also made available to us.

Previous studies have focused on the unique feeding behaviour of the Komodo Dragon but have not related this to its unique dental morphology, development, and replacement. We, therefore, examined the dentition and jaws of adults and juveniles with a combination of histological analysis and computed tomography (CT). We discovered that the adult Komodo teeth were surprisingly similar to those of theropod dinosaurs, with the strongly recurved teeth of adults having serrated cutting edges that were strengthened by dentine cores. “We were very excited by this discovery because it makes the Komodo an ideal living model organism for studies of the life history and feeding strategies of the extinct theropod dinosaurs” said PhD student Tea Maho, lead author of the paper published in PLoS One.

The Komodo Dragon, like most other reptiles, including the extinct theropod dinosaurs, replaces its teeth continuously throughout its life. The histology, a common technique for studying the microstructure of teeth, and x-ray CT of their heads showed that the Komodo dragon maintains up to five replacement teeth per tooth position in their jaws. “Having this many teeth within the jaw at a given time is a unique feature among predatory reptiles, and only seen In the Komodo” noted Dr. Robert Reisz, coauthor of the research paper.  Most other known reptiles have one or at most two replacement teeth in the jaw, and this includes most theropod dinosaurs. Perhaps the most surprising discovery was that the Komodo started to make new teeth in each tooth position every 40 days. This is why there were so many shed teeth in the Komodo Dragon enclosure, and this is how new teeth very rapidly replace the old functional teeth. Other reptiles, including most theropod dinosaurs, usually took three months to make a replacement tooth, sometimes as long as a year. “So, if in the wild a tooth breaks during prey capture or defleshing, no problem, a new one would replace the broken tooth very quickly” explained Tea Maho.

Since we had skulls and teeth of both adults and juveniles of the Komodo, we were also able to discover an interesting correlation between their teeth and their feeding behaviour. Hatchlings and juvenile Komodos have more delicate teeth, not suited for the typical defleshing behaviour of the adults, and spend most of their time in the trees, avoiding the adults and feeding mainly on insects and small vertebrates. As they grow to adult size, their teeth change dramatically in shape, and they eventually descend from the trees to become apex predators, able to attack and kill anything in their domain.

Finally, we also noticed that the front teeth of the Komodo adults are either very small or completely missing. This unusual dental morphology correlates well with their tongue-flicking behaviour, using the slender, forked snake-like tongue for foraging for prey without having to open their mouth.

Shed teeth, histology and X-ray CT reveal exceptionally rapid tooth development in the largest living lizard

CREDIT

Tea Maho, University of Toronto Mississauga

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0295002 

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Exceptionally rapid tooth development and ontogenetic changes in the feeding apparatus of the Komodo dragon

ARTICLE PUBLICATION DATE

7-Feb-2024