Category: Science

Research Findings: High-Power Ultrasound Improves the Quality of Spanish Rosé Wine

A recent study by Spanish researchers concluded that ultrasound improves wine quality by shortening maceration time.

In 2019, The International Organization of Vine and Wine (OIV) approved the use of ultrasound to favor the extraction of grape compounds, its application in obtaining superior quality red wines has been widely studied.

Spanish researchers have turned their attention to rosé, a booming market that has experienced strong growth over the past 15 years. A research team from the University of Castilla-La Mancha, and the University of Murcia in Spain used high-powered ultrasound technology to treat crushed Monastrell grapes, a process known as sonication. They compared the resulting rosé with the wine obtained after a four-hour maceration period.

The research team described the improvements in color and sensory profile of the sonicated wine compared to the macerated sample, here are their findings: https://onlinelibrary.wiley.com/doi/10.1002/jsfa.12757

Professor Encarna Gómez Plaza, from the University of Murcia explained the importance of the research for the wine industry. He stated that “the ultrasonic application was primarily designed to reduce maceration time in red wine vinification. However, experiments with white wines have shown that the aromatic fraction can be increased by sonicating crushed grapes. Therefore, we decided to study the effect of ultrasound on rosé wines, something that had not been done before.”

Prolonged maceration can cause oxidation of certain compounds in the wine, leading to a bitter taste and other undesirable effects.. This is where ultrasounds come in. Ultrasonic sonication causes the cells in the skin of the grape to rupture, allowing the desirable compounds to be extracted in a significantly shorter steeping time, thus reducing the adverse effects of oxidation.

Sensory analysis of the wines by a panel revealed that the ultrasonic rosé had superior aromas

“Sonication resulted in wines with intense aromas of red fruits and flowers, with higher scores than wines from macerated grapes,” the authors note.

Analysis of the chemical composition supported this claim: ultrasonication improved the extraction of several volatile aroma-enhancing compounds, such as terpenes, which can give off a floral or citrus fragrance.

The team hopes that this study will draw attention to the potential of ultrasonic technology to produce high-quality rosé wines. Now they are studying other applications of high-power ultrasound in the wine industry.

Ancient wine grapes related to today’s grape varieties, research shows

“A recent international study led by two Israeli universities analyzed 1,000-year-old seeds which were discovered at archaeological excavations in the Negev; the findings are ‘significant for Israel’s modern wine industry” research scientist states

A recent study led by the paleogenetic laboratory of the Steinhardt Museum of Natural History at Tel Aviv University and the University of Haifa analyzed DNA from ancient local wine grape seeds discovered at archaeological excavations in the Negev.

One seed was found to be almost identical to the Syriki variety used today to make high-quality red wine in Greece and Lebanon, while another seed is a relative of the white variety called Be’er, still growing in deserted vineyards in the dunes of Palmachim.

The genetic study was led by Dr. Pnina Cohen and Dr. Meirav Meiri of the paleogenetic lab at the Steinhardt Museum of Natural History at Tel Aviv University. The seeds were found at archaeological excavations led by Prof. Guy Bar-Oz from the School of Archaeology and Maritime Cultures at the University of Haifa, in collaboration with researchers from the Israel Antiquities Authority. Other participants included researchers from the University of Haifa, the Weizmann Institute, Bar-Ilan University, and research institutions in France, Denmark, and the U.K. The paper was published in the journal Proceedings of the National Academy of Sciences.

“Archaeological excavations conducted in the Negev [Israel] in recent years have revealed a flourishing wine industry from the Byzantine and early Arab periods (around the fourth to ninth centuries A.D.), especially at the sites of Shivta, Haluza, Avdat, and Nizana, which were large, thriving cities at the time,” says Prof. Guy Bar-Oz from the University of Haifa.

“The findings include large winepresses, jugs in which the exclusive wine, exported to Europe, was stored, and grape seeds preserved for more than a thousand years. This industry gradually declined following the Muslim conquest in the 7th century, since Islam forbids the consumption of wine.”

“The cultivation of wine grapes in the Negev was renewed only in

Modern times, in the state of Israel, mostly since the 1980s. This industry, however, relies mainly on wine grape varieties imported from Europe.”

One especially interesting finding was a large hoard of grape seeds, discovered on the floor of a sealed room at Avdat. The researchers explain that these seeds have been relatively well-preserved thanks to protection from climatic phenomena such as extreme temperatures, flooding, or dehydration. To learn more about the seeds, in the hope of discovering which varieties they might belong to, the researchers prepared to extract their DNA in the paleogenetic lab.

“The science of paleogenomic uses a range of advanced technologies to analyze ancient genomes, primarily from archaeological findings,” explains Dr. Meiri from the Steinhardt Museum of Natural History at Tel Aviv University.

“Since the DNA molecule is very sensitive and disintegrates over time, especially under high temperatures, we usually get only small pieces of DNA, often in a poor state of preservation. To protect them we work under special conditions: the paleogenetic lab is an isolated clean laboratory, with positive air pressure that keeps contaminants out, and we enter it in sterilized ‘spacesuits’ familiar to everyone from the COVID pandemic.”

To begin with, the researchers looked for any organic matter remaining in the seeds. For this purpose, they used FTIR (Fourier-transform infrared spectroscopy)—a chemical technique applying infrared radiation to produce a light spectrum that identifies the sample’s content. Finding remnants of organic matter in 16 seeds, the researchers went on to extract DNA from these samples.

The extracted DNA was sequenced, with an emphasis on about 10,000 genomic sites where variety-specific features are usually found, and the results were compared to databases of modern grapevines from around the world: In 11 samples, the quality of genetic material was too poor to allow any definite conclusions. Three of the remaining samples were identified as generally belonging to local varieties. Finally, the two samples of the highest quality, both from around 900 A.D., were identified as belonging to specific local varieties that still exist today.

Further details found here:

https://phys.org/news/2023-05-international-reveals-genetic-link-modern.html

Sources:

Tel-Aviv University, and
National Academy of Sciences