Viticulture and Oenology Commons^™

Evaluating Fungicide Programs For Grapevine Disease Management And Fungicide Sensitivity Monitoring, Abraham Ahumada

Master's Theses

Grapevine diseases, such as powdery mildew and Botrytis bunch rot, require repeated fungicide applications to maintain fruit quality and reduce yield losses. However, fungicide performance can vary among products, application programs, disease pressure, and pathogen sensitivity. This thesis evaluated fungicide programs for control of powdery mildew in ‘Chardonnay’ grapes and assessed fungicide sensitivity of Botrytis cinerea isolates collected from California vineyards.

Powdery mildew, caused by the fungal pathogen Erysiphe necator, is a major threat to the production of Vitis vinifera grapes worldwide. Because powdery mildew management relies heavily on fungicide applications, field evaluations are needed to compare the efficacy …

Chemical And Sensory Consequences Of Oxidative And Reductive Handling Of White Wines, Amelia Pargellis

Master's Theses

In the 2024 and 2025 vintage four experiments were performed each with a different varietal, namely Albariño, Grenache blanc, Loureiro, and Vermentino. These experiments investigated the effects of hyperoxygenation, reductive winemaking techniques, while monitoring the oxidation-reduction potential.

Albariño grapes were made following two juice protocols, control/reductive (Reductive Control) and oxidative (HyOx). Reductive Control received antioxidants (50 ppm SO₂, 160 mg/L ascorbic acid) and CO₂ blanketing, and HyOx underwent hyperoxygenation at approximately 700 mL/L/h of air for two hours through a stainless-steel sparging stone with 10-µm pores. Juice was cold-settled and racked. Reductive Control juice was split into …

Measurement And Control Of The Oxidation-Reduction Potential And Its Chemical And Sensory Consequences In Wines, William Jordan Wright

Master's Theses

The oxidation-reduction potential (ORP) is a measurement thought to reflect the overall ability of a solution to oxidize or reduce substances within that solution. In wine, there is no absolute agreement as to which substances control or dominate the ORP; however, oxygen, ethanol, iron-tartrate and copper-tartrate complexes, and glutathione are suspected to play key roles, while sulfur dioxide and phenolics may act as buffers. Anecdotally, some varieties of Vitis vinifera are prone to oxidation while others are prone to reduction, though the chemical basis of this remains unclear. The following works aim to further elucidate the influence of specific chemical …

Evaluating Nanobubble-Enriched Water Treatments For Cleaning Stainless Steel Winery Tanks At The Gallo Winery Research Station In Livingston, California, Edgar Godoy-Garcia

Master's Theses

ABSTRACT

Evaluating nanobubble-enriched water treatments for cleaning stainless steel winery tanks at the Gallo winery research station in Livingston, California.

Edgar A. Godoy-Garcia

Sanitation of stainless steel wine storage tanks is a critical component of quality control in commercial winemaking operations. Ineffective cleaning can lead to microbial contamination, product spoilage, and safety concerns. Traditionally, wineries rely on manual scrubbing, chemical cleaning agents, and extensive water rinsing cycles to maintain sanitary tank conditions. However, these methods are resource-intensive and may pose risks to both workers and the environment due to chemical exposure and wastewater generation. In response to growing industry interest …

The Temporal Evaluation Of Mouthfeel And Retronasal Sensations In Red Wines From The Central Coast Of California, Emily S. Stoffel

Master's Theses

Time-based sensory analysis techniques capture the dynamic retronasal and mouthfeel sensations in wines. It is important to understand how common winemaking practices and popular varietals impact the retronasal and mouthfeel profile as consumers tend to judge wine quality based on the taste, flavor, and mouthfeel of a wine. Three time-based sensory analysis methods were utilized with the objective to understand the effect of five commonly applied winemaking techniques (blending, varietal choice, fermentation temperature, cap management, and stem addition) on the dynamic retronasal and mouthfeel profile of six different varietals (Merlot, Malbec, Petite Sirah, Pinot noir, Grenache, and Tannat) grown on …

Determination Of Fungicide Resistance In Botrytis Cinerea On Wine Grapes In California's Central Coast Region, Evelyn Alvarez-Mendoza

Master's Theses

Botrytis bunch rot, caused by Botrytis cinerea, is a fungal disease that primarily affects the fruit of wine grapes. Infection of fruit consequently results in reduced yields and wine quality. These factors lead to significant economic losses for growers which prompts the implementation of management practices to control the disease. One objective of this study was to evaluate the level of resistance that populations of B. cinerea in the Central Coast region showed to various chemicals. A fungicide assay was conducted to determine resistant phenotypes to six fungicide active ingredients (pyrimethanil, iprodione, fenhexamid, fludioxonil, trifloxystrobin, boscalid). Thirty-five (2020) and …

Cofermentation, Post-Alcoholic, And Post-Malolactic Fermentation Blending Of Malbec, Merlot And Petite Sirah Wines, Armando Arturo Vega-Osorno

Master's Theses

A two-year study was conducted to assess the effects of cofermentation on red wine varietals. During the winemaking process, wines can be made from two or more varieties by picking, crushing and fermenting them together, a practice known as cofermentation. They can also be blended either after the completion of alcoholic fermentation or after malolactic fermentation. In the first year of the study, two grape varieties, Merlot (Mer), and Malbec (Mal) were cofermented. On the second year, a third varietal, Petite Sirah (PS) was also studied. Cofermented wines containing every possible binomial combination of the varietals was made and one …

Effect Of Vine Age And Selected Winemaking Techniques On The Sensory Profile Of Central Coast Red Wines, Isabelle Lomonaco

Master's Theses

Descriptive sensory analysis is essential to understanding how differing varietals, viticultural techniques, enological techniques, vintage, regions, etc. impact the sensory characteristics found in wines. These studies analyzed the sensory impacts of vine age, whole cluster and stem addition influences, the frequency of cap management regimes, and selected fermentation variables, on 2019 Zinfandel, 2020 Syrah, 2020 Tannat, 2020 Cabernet Sauvignon, and 2021 Graciano wines respectively, from the Central Coast of California, USA. The investigation of Old vine Zinfandel indicated that these wines were defined as complex due to the wide variety of descriptors used to characterize them, having high color saturation …

Climate Adaptation And Water Conservation Decision-Making In Paso Robles, California Vineyards, Christopher R. Klier

Master's Theses

This paper examines vineyard perceptions and adoption of climate change adaptation and water conservation measures in the Paso Robles American Viticultural Area (AVA). A survey was distributed to all 220 vineyards and vineyard management companies that operate in the AVA, with a 53.64% response rate. The objective of the survey was to determine vineyard manager and owner attitudes towards climate change and adaptation, as well as their perceptions of how these threats would impact their operation. A second objective was to document the current level of water conservation and climate adaptation while identifying the barriers and opportunities for further adoption …

The Effects Of Vine Age On Vine Performance, Fruit, And Wine Composition Of Zinfandel In The Templeton Gap Ava, California, Vegas L. Riffle

Master's Theses

A two-year study was conducted at a commercial vineyard in California’s Templeton Gap AVA to evaluate the effect of vine age on viticultural, enological, and sensory attributes of Vitis vinifera L. cv. Zinfandel grapes and wines. The experimental block was dry farmed, conventionally managed, with own-rooted Zinfandel vines that, when determined unproductive, were replaced with new vines of genetically identical scion plant material grafted onto St. George (Vitis rupestris Scheele) rootstock. Treatments included Young vines (5 to 12 years old), Control (representative proportion of young to old vines in the block), and Old vines (40 to 60 years old). …

The Effects Of Cluster Thinning On Vine Performance, Fruit, And Wine Composition Of Pinot Noir (Clone 115) In The Edna Valley Of California, Paul F W Mawdsley

Master's Theses

A three-year study was conducted at a commercial vineyard site in California’s Edna Valley AVA to evaluate the physiological and agronomical effects of the timing of cluster thinning on Pinot noir (clone 115) grapevines. Vines were thinned to one cluster per shoot at three selected time-points during the growing season (bloom, bloom + 4 weeks, bloom + 8 weeks), and fruit from each treatment was harvested and made into wine. Across all growing seasons, yield decreased 43% in thinned vines relative to un-thinned control vines. No effect of cluster thinning or interaction with growing season was found in vine shoot …