Browsing by Author "Stewart, Amanda C."

Now showing 1 - 20 of 51
  • Thumbnail Image
    Acetone, Butanol, and Ethanol (ABE) Production from Food Waste via Clostridium beijerinckii
    Poe, Nicholas Edward (Virginia Tech, 2020-01-28)
    Annually, approximately 150 million metric tonnes of food goes to waste in the U.S., potentially causing economic loss and environmental pollution. Fermentation of food waste to produce acetone, butanol and ethanol (ABE) via fermentation has the potential to valorize food waste by producing value-added chemicals. However, the composition of food wastes from different sources vary, which affects ABE fermentation performance and hinders the commercialization of food waste fermentation. The objective of this study is to investigate the compositional variation of food waste collected weekly for 16 weeks (a total of sixteen samples) and determine how this variation affects ABE fermentation performance. Samples collected from Southgate Center, a food processing facility operated by Virginia Tech Dining Services, was characterized for use as a feedstock for ABE fermentation. Water, sugar, starch, fiber, protein, fat and ash concentrations in each of food waste samples were determined. ABE fermentation of these wastes was performed using Clostridium beijerinckii via batch fermentations. Correlations of ABE and butanol yields with the individual components of food waste composition were performed to better understand which components are key to ABE fermentation. Overall, this study demonstrated the feasibility of using food waste as a viable feedstock for ABE fermentation and investigated the effect of variation of food waste composition on the ABE fermentation performance. In the 16 collected samples, each major compositional attribute exhibited high variability. The concentration of total soluble sugar, defined as glucose, fructose, sucrose for the purposes of this experiment, ranged from 0.5 to 53.5% (dry basis) among different food waste samples. The concentration ranges of total starch, neutral detergent fiber (NDF), crude protein, crude fat and ash were 0 to 23.4% (dry basis), 0.6 to 25.8%, 5.5 to 21.2%, 0.1 to 37.9%, 1.4 to 13.7%, respectively. The high variation of food waste composition resulted in a high variation of ABE yield when these food wastes were subjected to fermentation by C. beijerinckii. The total ABE concentration following fermentation ranged between 6.9 to 17.0 g/L with an average value of 13.2 g/L. ABE and butanol concentrations are positively correlated with starch and equivalent glucose, i.e., the sum of initial free glucose and glucose that could be theoretically hydrolyzed from starch and sucrose during fermentation, but is negatively correlated with NDF concentrations.
  • Thumbnail Image
    Amorphous solid dispersion effects on in vitro solution concentrations of quercetin
    Gilley, Andrew (Virginia Tech, 2016-08-31)
    Quercetin is a flavonol with potential health benefits including activities against cardiovascular disease, obesity, and oxidative stress. However, the benefits of quercetin are likely limited by poor bioavailability, primarily attributed to its poor aqueous solubility (due to its hydrophobicity and crystallinity) and extensive phase-II metabolism. Improving the apparent solubility of quercetin has the potential to improve its in vivo bioavailability. Strategies to increase solution concentrations in the small intestinal lumen have the potential to substantially increase quercetin bioavailability, and efficacy. We aimed to achieve this by incorporating quercetin into amorphous solid dispersions (ASDs) with cellulose derivatives, eliminating crystallinity, and selectively releasing amorphous quercetin under simulated intestinal conditions (pH 6.8, 37C). Amorphous quercetin was dispersed in cellulose esters including 6-carboxycellulose acetate butyrate (CCAB), hydroxypropylmethylcellulose acetate succinate (HPMCAS) and cellulose acetate suberate (CASub) to achieve stability and provide pH-triggered release. In addition, polyvinylpyrrolidone (PVP) containing CASub and CCAB blends were prepared to further promote enhanced dissolution. The ASD employing 10% quercetin in 20% PVP:70% CASub was most successful at enhancing the solution concentration of quercetin, providing an 18-fold increase in the area under the concentration/time curve (AUC) compared to quercetin alone. These results warrant in vivo assessment of quercetin-loaded ASDs formulated with CASub and its blend with PVP towards improving the bioavailability of quercetin.
  • Thumbnail Image
    Anti-Diabetic and Anti-Obesity Activities of Cocoa (Theobroma cacao) via Physiological Enzyme Inhibition
    Ryan, Caroline Mary (Virginia Tech, 2016-06-01)
    Fermentation and roasting of cocoa (Theobroma cacao) decrease levels of polyphenolic flavanol compounds. However, it is largely unknown how these changes in polyphenol levels caused by processing affect cocoa's anti-diabetic and anti-obesity bioactivities, such as inhibition of certain enzymes in the body. Polyphenol profiles, protein-binding abilities, presence of compounds termed oxidative polymers, and abilities to inhibit α-glucosidase, pancreatic α-amylase, lipase, and dipeptidyl peptidase-IV (DPP4) in vitro were compared between unfermented bean (UB), fermented bean (FB), unfermented liquor (UL), and fermented liquor (FL) cocoa extracts. Overall, there were significant decreases (p<0.05) in total polyphenols, flavanols, and anthocyanins between the two sets of unfermented and fermented cocoa extracts (CEs). All CEs effectively inhibited α-glucosidase (lowest IC50 = 90.0 ug/mL for UL) and moderately inhibited α-amylase (lowest IC50=183 ug/mL for FL), lipase (lowest IC25=65.5 ug/mL for FB), and DPP4 (lowest IC25=1585 ug/mL for FB) in dose-dependent manners. Fermentation and roasting of the samples affected inhibition of each enzyme differently (both processes enhanced α-amylase inhibition). Improved α-glucosidase and α-amylase inhibitions were correlated with presence of different classifications of oxidative polymers, suggesting that these compounds could be contributing to the bioactivities observed. Some α-glucosidase inhibition might be due to non-specific protein-binding. Improved DPP4 inhibition was strongly correlated to increased CE degree of polymerization. In conclusion, potential enzyme inhibition activities of cocoa were not necessarily negatively affected by the large polyphenol losses that occur during fermentation and roasting. Additionally, it is possible that more complex compounds could be present in cocoa that contribute to its potential anti-diabetic and anti-obesity bioactivities.
  • Thumbnail Image
    Appeal of the Apple: Exploring consumer perceptions of hard cider in the Northeast and Mid-Atlantic United States
    Calvert, Martha D.; Neill, Clinton L.; Stewart, Amanda C.; Chang, Elizabeth A. B.; Whitehead, Susan R.; Lahne, Jacob (Taylor & Francis, 2023-10-23)
    Alcoholic or “hard” cider is experiencing a resurgence in popularity, particularly throughout the Northeast and Mid-Atlantic regions of the United States. Yet, many stakeholders struggle to understand how consumers define and distinguish hard cider from the sea of options in the saturated alcoholic beverage market. This study aimed to explore consumer preferences for hard cider using a phenomenological, qualitative approach. The research comprised 14 focus groups with regular cider consumers (99 participants) throughout three leading cider-producing states in the Northeast and Mid-Atlantic United States: Virginia, Vermont, and New York. All focus group sessions were subject to reflexive thematic analysis for themes broadly related to cider product preference and the cider-drinking experience. Results of the study suggest that cider preference is motivated largely by sensory quality in addition to various other factors including perceived health effects, regionality and proximity, the drinking occasion, and product information. Results also emphasize the importance of nostalgia in cider sensory experiences, as well as the role of social norms in consumer valuation of cider products. Overall, this research highlights diverse consumer preferences for cider and serves as a framework for using qualitative research methods to explore consumer preferences in the food and beverage industries.
  • Thumbnail Image
    Appeal of the Apple: Investigating Preference, Perception, and Communication Around Hard Cider in the Northeast and Mid-Atlantic United States
    Calvert, Martha D. (Virginia Tech, 2023-07-03)
    Alcoholic or "hard" cider, as it is known in the United States, is experiencing a resurgence in popularity worldwide, but most relevantly throughout the Northeast and Mid-Atlantic regions of the United States. Cider has a rich history of being America's drink of choice, beginning with the native apple trees of indigenous communities and the proliferation of apple growing in the original American colonies. Today, cider is becoming popular particularly in the Northeast and Mid-Atlantic where New York, Virginia, and Vermont are the 1st, 8th, 12th ranked states with the most cideries in America. In light of the American cider industry experiencing such a renaissance, leading industry stakeholders and various other scholars have drawn attention to the need for increased clarity regarding consumer and producer perceptions of cider quality, as well as a more comprehensive understanding of cider sensory quality. This dissertation utilizes qualitative research methods, including focus groups and interviews conducted in New York, Virginia, and Vermont, to explore consumer and producer preferences of cider and the cider-drinking experience. In addition, this research employed traditional sensory descriptive analysis (DA) to quantify sensory differences across cider products. Lastly, this research presents findings on the use of biterm topic modeling (BTM), an emergent method of text mining for small datasets, to explore topics of discussion in cider marketing materials for products in the American cider marketplace. This dissertation presents evidence of preferences, sensory perception, and discourse within a snapshot of the current American cider industry. Cider consumers and producers prioritize flavor when discussing cider quality, but also value how cider is made and where it comes from. Consumers, in particular, are nostalgic about the cider-drinking community and culture that is omnipresent in the Northeast. Secondly, the sensory quality of ciders can be discriminated across multiple variables, including region of origin, packaging, and style; suggesting that the sensory space of American cider products is diverse and nuanced. Lastly, when marketing cider products through website platforms, cider producers tend to emphasize topics related to sensory attributes, production elements, food-pairing, flavorings, and apple varieties. With a greater understanding of consumer and producer preferences of cider, cider sensory quality, and cider communication, industry actors and stakeholders may have a more actionable understanding of where the cider industry may be headed with continued growth. As well, this dissertation provides a framework for the use of qualitative and text mining tools to better understand facets of consumption and production, as well as marketing language in the food and beverage space.
  • Thumbnail Image
    Assessment of Vineyard Nitrogen Management upon Grape Chemistry
    Moss, James Russell (Virginia Tech, 2016-07-29)
    To combat excessive vine vigor, many vintners have employed intensive cover cropping techniques. While cover crops provide a multitude of benefits to the farming system, they can compete for nutrients and water. The seemingly ubiquitous adoption of cover crops in the Eastern United States has led to vines and grape musts which are deficient in nitrogen (N). A must that is deficient in yeast assimilable nitrogen (YAN) can lead to the production of off aromas and stuck or sluggish fermentations. It has also been suggested that musts with limited amino nitrogen sources can result in wines with less fruity aromas than those with a higher starting amino acid content. Varying rates of calcium nitrate were applied to the soil at bloom and foliar urea was sprayed at a Sauvignon blanc and Petit Manseng (Vitis vinifera L.) vineyard. Perennial White and Crimson clover as well as foliar urea applications at véraison were utilized at a Vidal blanc (Vitis spp.) site. Foliar urea was effective at significantly increasing YANs in all experiments with some year to year variation in efficacy. Foliar urea applications slightly favored the production of ammonia over primary amino nitrogen. While most of the measured amino acids in fruit increased in concentration with the application of either soil or foliar N, foliar applications were more effective at increasing fruit amino acids. Of the amino acids measured, arginine and glutamine were the most increased by foliar urea applications, whereas proline was relatively unaffected. The use of clover as a perennial under-vine cover crop did not increase berry YAN. The application of foliar urea sprays may present an effective means by which vintners can easily increase must YANs and amino acid contents.
  • Thumbnail Image
    Can Cider Chemistry Predict Sensory Dryness? Benchmarking the Merlyn Dryness Scale
    Calvert, Martha D.; Cole, Elizabeth; Stewart, Amanda C.; Neill, Clinton L.; Lahne, Jacob (Taylor & Francis, 2022-09-23)
    The growing popularity of hard cider in the United States has been accompanied by an inconsistent understanding of the nature and importance of consumers’ perception of dryness and sweetness in the product. In 2018, the New York Cider Association proposed the Merlyn Dryness Scale as a tool to predict cider dryness using basic cider chemistry, but this approach has yet to be validated in sensory experiments. In the current study, panelists (N = 48) evaluated three different commercial ciders served at two different temperatures (2 °C and 22 °C) in three parts: by rating the dryness of the sample on a line scale equivalent to the range of the Merlyn Dryness Scale, by using a simple check-all-that-apply (CATA) tool that included dryness, and by rating their overall liking on a 9-point hedonic scale. The results indicated that the Merlyn Dryness Scale may not achieve its goal of predicting perceived dryness in cider, as consumers perceived cider samples to be more dry than was suggested using Merlyn Scale chemical procedures. Contrary to expectations, the serving temperature of the cider samples did not significantly impact perceived dryness rating but did influence overall liking. This study suggests that predicting sensory dryness from cider-chemistry parameters requires further study.
  • Thumbnail Image
    Comparing Extraction Methods in Sample Preparation for the Quantification of Cannabinoids in Industrial Hemp
    Sandbrook, Ann Marie (Virginia Tech, 2021-05-28)
    Industrial hemp is legally defined in the United States by the Agriculture Improvement Act of 2018 (2018 Farm Bill) as Cannabis containing <0.3% total tetrahydrocannabinol (THC). The 2018 Farm Bill does not, however, specify standard methods for sample preparation or quantification of cannabinoids (including THC) in Cannabis. Extraction efficiency of phytochemicals is well-known to depend on the solvent and extraction method used. In this project, we evaluated the effect of sample preparation extraction methods on the quantitative analysis of five cannabinoids found in industrial hemp with regulatory or commercial significance: cannabidiol (CBD), cannabidiolic acid (CBDA), delta-9-tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), and cannabinol (CBN). Extraction methods evaluated include: QuEChERS, diethyl ether, ethanol, and methanol. Extracts obtained via these methods were subject to quantitative cannabinoid analysis by UPLC/PDA. Standard curves for quantification of each cannabinoid were constructed using authentic standards for quantification. The concentrations of each cannabinoid in the plant material determined via each of the extraction methods were compared using one-way ANOVA followed by Tukey's HSD (significant difference defined as p <0.05). All extraction methods evaluated returned different concentrations of total THC in the plant material. The QuEChERS extraction resulted in the highest calculated concentrations of THC, THCA and CBDA, reporting three to four times greater than obtained via other extractions evaluated. Classification of the starting plant material as hemp or marijuana depended on the extraction method used. These findings clearly and quantitatively demonstrate the need for standardization of extraction methods for hemp analysis and regulation.
  • Thumbnail Image
    Comparison of Common Analytical Methods for the Quantification of Total Polyphenols and Flavanols in Fruit Juices and Ciders
    Ma, Sihui; Kim, Cathlean; Neilson, Andrew P.; Griffin, Laura E.; Peck, Gregory M.; O'Keefe, Sean F.; Stewart, Amanda C. (2019-07-17)
    Multiple analytical methods are used for quantification of total polyphenols and total flavanols in fruit juices and beverages. Four methods were evaluated in this study: Folin-Ciocalteu (F-C), Lowenthal permanganate (L-P), 4-dimethylaminocinnamaldehyde (DMAC), and the bovine serum albumin (BSA) precipitation method. Method validation parameters, including working range, limit of detection, limit of quantitation, precision (repeatability), accuracy, and specificity, were assessed and compared. The F-C method was not specific to polyphenols, and the L-P method had the widest working range but lacked accuracy. The DMAC method was the most specific to flavanols, and the BSA method was not suitable for quantification of smaller flavanols, such as catechin and epicatechin. Quantitative performance was evaluated using commercial fruit juice samples (n = 14), apple juice samples of different cultivars (n = 22), and commercial ciders (n = 17). In general, the L-P titration method and DMAC method resulted in higher quantitative values than the F-C method and BSA precipitation method, respectively. However, ratios of results obtained by the L-P and F-C method ranged from 1 to 28, and ratios of results obtained by the DMAC and BSA precipitation method ranged from <1 to 280. This tremendous variation is likely due to variation in polyphenol composition and sample matrix. This information provides perspective for comparison of results obtained through these different methods, and a basis for choosing the most appropriate analytical method for quantification of polyphenols to address a specific research question when working with commercial fruit juice, apple juice from different apple cultivars, and commercial ciders. Practical Application This study compared results obtained when four common polyphenol quantification methods were applied to a diverse selection of fruit juices and beverages with distinct polyphenol composition and sample matrix. The matrix and polyphenol composition of the samples significantly influenced the results. Our findings can help manufacturers of fruit-based products choose the most appropriate analytical method for polyphenol quantification as part of a quality assurance program or to convey information on dietary polyphenol content to consumers. An assessment of analytical method validation parameters is provided for each of the four methods, which will help users of these methods to understand their limitations.
  • Thumbnail Image
    Compositional Characterization of Different Industrial White and Red Grape Pomaces in Virginia and the Potential Valorization of the Major Components
    Jin, Qing; O’Hair, Joshua; Stewart, Amanda C.; O'Keefe, Sean F.; Neilson, Andrew P.; Kim, Young Teck; McGuire, Megan N.; Lee, Andrew H.; Wilder, Geoffrey; Huang, Haibo (MDPI, 2019-12-11)
    To better evaluate potential uses for grape pomace (GP) waste, a comprehensive chemical composition analysis of GP in Virginia was conducted. Eight commercial white and red pomace samples (cv. Viognier, Vidal Blanc, Niagara, Petit Manseng, Petit Verdot, Merlot, Cabernet Franc, and Chambourcin) obtained from different wineries in Virginia, USA were used. For extractives, GPs contained 2.89%–4.66% titratable acids, 4.32%–6.60% ash, 4.62%–12.5% lipids with linoleic acid being the predominant (59.0%–70.9%) fatty acid, 10.4–64.8 g total phenolic content (gallic acid equivalents)/kg GP, 2.09–53.3 g glucose/kg GP, 3.79–52.9 g fructose/kg GP, and trace sucrose. As for non-extractives, GPs contained 25.2%–44.5% lignin, 8.04%–12.7% glucan, 4.42%–7.05% xylan, and trace amounts of galactan, arabinan, and mannan (less than 3% in total). Potential usages of these components were further examined to provide information on better valorization of GP. Considering the valuable extractives (e.g., polyphenols and oil) and non-extractives (e.g., lignin), designing a biorefinery process aiming at fully recover and/or utilize these components is of future significance.
  • Thumbnail Image
    Consumer Acceptance of Beer: An Automated Sentiment Analysis Approach
    Canty, Ellise Adia (Virginia Tech, 2022-07-13)
    Selecting the correct methodology to better understand how consumers perceive food products is a challenging task for the food industry and sensory researchers alike. Free comment tasks (FC) utilize the advantages of open-ended questions to generate intuitive comments from untrained consumers to help identify and describe sensory attributes of products. However, FC data is typically analyzed using text analysis done by hand and is very cumbersome to organize and interpret. There is a growing need and interest to add to the library of data analysis tools used to understand FC data and consumer acceptance studies. Sentiment analysis is an opinion mining tool commonly used in marketing and computer science that extracts the emotional valence of the author from an unstructured text in the form of a sentiment score. A few studies in sensory evaluation use lexicon-based sentiment analysis which has many drawbacks: it is time-consuming, requires a large amount of data and dictionaries need to be tailored for food. We used a deep learning sentiment analysis approach to analyze and predict consumer sentiment/acceptance. The research objectives of this study are 1) to explore quicker and automated methods of sentiment analysis to better understand and predict consumer acceptance, and 2) to examine the advantages and disadvantages of sentiment analysis as a data analysis tool in sensory evaluation. We avoided the pitfalls of creating a sentiment lexicon by using online beer reviews to train a word embedding model where all of the relevant words in the review are converted into vectors. We used the distance and similarity (clustering) of the vectors to determine taste/flavor attributes that correspond to negative and positive sentiment. Next, to validate and test our model we gathered FC data in a consumer acceptance study. Panelists (N=68) were presented with six beers, one at a time and were instructed to taste and smell before leaving comments. We performed sentiment analysis on the FC data, and we compared our deep learning sentiment analysis model with three other pre-existing sentiment analysis models: SentimentR, VADER, and Liu and Hu opinion lexicon. Our deep learning sentiment analysis model had the highest accuracy (69%) and precision rate (73%). Overall, our findings provide an early look into the advantages and disadvantages of sentiment analysis applied to FC data in sensory evaluation.
  • Thumbnail Image
    Crop Load Density Affects 'York' Apple Juice and Hard Cider Quality
    Peck, Gregory M.; Boudreau, Thomas F. IV; McGuire, Megan N.; Stewart, Amanda C. (2016-09-01)
    To assess the impact crop load has on hard cider chemistry, ‘York’ apple (Malus3domestica Borkh.) trees were hand thinned to three different crop loads: low [two apples per cm2 branch cross-sectional area (BCSA)], medium (four apples per BCSA), and high (six apples per BCSA). Higher crop loads produced smaller, less acidic fruit that were slightly more mature. In juice made from fruit from these treatments, the total polyphenol content did not differ at harvest, but, after fermentation, the medium crop load had 27% and the high crop load had 37%greater total polyphenol content than the low crop load. Yeast assimilable nitrogen (YAN) concentration in juice made from fruit from the low crop load treatment had 18%and 22% greater than the medium and high crop load, respectively. YAN concentrations in juice from the medium and high crop load treatments were similar. Our results provide apple growers and hard cider producers with a better understanding of how apple crop load impacts YAN concentrations in juice and total polyphenol concentrations in juice and cider.
  • Thumbnail Image
    Development and Characterization of a Pilot-Scale Model Cocoa Fermentation System Suitable for Studying the Impact of Fermentation on Putative Bioactive Compounds and Bioactivity of Cocoa
    Racine, Kathryn C.; Lee, Andrew H.; Wiersema, Brian D.; Huang, Haibo; Lambert, Joshua D.; Stewart, Amanda C.; Neilson, Andrew P. (MDPI, 2019-03-19)
    Cocoa is a concentrated source of dietary flavanols—putative bioactive compounds associated with health benefits. It is known that fermentation and roasting reduce levels of native flavonoids in cocoa, and it is generally thought that this loss translates to reduced bioactivity. However, the mechanisms of these losses are poorly understood, and little data exist to support this paradigm that flavonoid loss results in reduced health benefits. To further facilitate large-scale studies of the impact of fermentation on cocoa flavanols, a controlled laboratory fermentation model system was increased in scale to a large (pilot) scale system. Raw cocoa beans (15 kg) were fermented in 16 L of a simulated pulp media in duplicate for 168 h. The temperature of the fermentation was increased from 25–55 °C at a rate of 5 °C/24 h. As expected, total polyphenols and flavanol levels decreased as fermentation progressed (a loss of 18.3% total polyphenols and 14.4% loss of total flavanols during fermentation) but some increases were observed in the final timepoints (120–168 h). Fermentation substrates, metabolites and putative cocoa bioactive compounds were monitored and found to follow typical trends for on-farm cocoa heap fermentations. For example, sucrose levels in pulp declined from >40 mg/mL to undetectable at 96 h. This model system provides a controlled environment for further investigation into the potential for optimizing fermentation parameters to enhance the flavanol composition and the potential health benefits of the resultant cocoa beans.
  • Thumbnail Image
    The Development of a Lexicon for Virginia Ciders through Descriptive Analysis
    Cole, Elizabeth Jane (Virginia Tech, 2022-06-08)
    Hard cider or "cider" is a fermented, alcoholic beverage made from the juice of apples. The cider industry has experienced recent growth within the United States and Virginia. Virginia is one of the largest producers of apples in the United States, and apples are considered a top commodity in the state. Currently, there is inconsistent terminology to describe Virginia cider, and cider producers are using descriptors that are usually associated with beer and wine. Thus, this study aims to identify the distinct sensory profiles of Virginia ciders and to identify drivers of consumer liking. Understanding sensory profiles and drivers of consumer liking for Virginia ciders will aid consumers in understanding what kind of cider styles they prefer and could help producers identify acceptable cider products. A descriptive analysis (DA) was completed to determine a well-defined sensory profile for Virginia hard ciders. The DA consisted of 24 ciders that producers considered to be representative of Virginia and their brands from 16 of the 32 known cider producers in Virginia. In the DA, 6 panelists defined reference standards for 48 descriptors consisting of 20 aromas, 3 tastes, 13 flavors, and 12 mouthfeel attributes. Through M/ANOVA, 22 descriptors were identified as significant, and 6 groups of ciders were identified using Hierarchical Cluster Analysis (HCA). Then, an exploratory consumer study using 8 representative ciders from the DA was conducted with 67 subjects. Subjects were first asked a series of demographic questions, then presented with samples in randomized, sequential, monadic fashion and reported overall liking, purchasing intent, and willingness to pay. Internal and external preference mapping was accomplished with Partial Least Squares Regression (PLS) and Clustering Around Latent Variables (CLV). Three distinct clusters were identified with distinct product and sensory preferences. Finally, basic chemical analyses of all samples were performed. The DA demonstrated that Virginia ciders have distinct sensory characteristics and fall into distinct sensory groups. The 3 consumer clusters found through CLV may represent cider drinkers' preferences in both Virginia and the United States. While no unusual cider chemistry was found, we were able to observe expected connections between chemistry and sensory profiles.
  • Thumbnail Image
    Discovery and dissemination of new knowledge in food science: Analytical methods for quantification of polyphenols and amino acids in fruits and the use of mobile phone-based instructional technology in food science education
    Ma, Sihui (Virginia Tech, 2019-06-11)
    The discovery and dissemination of new knowledge are essential in food science. To advance our understanding of fruit chemistry, analytical methods were compared and applied. Polyphenols are secondary metabolites in fruits of particular importance in food science, as they contribute to the sensory attributes and health benefits of the products. Evaluation of common analytical methods for the quantification of polyphenols, including the Folin-Ciocalteu (F-C), Lowenthal permanganate (L-P), 4-dimethylaminocinnamaldehyde (DMAC) and the bovine serum albumin (BSA) precipitation methods, was conducted using analytical method validation procedures. The F-C method was not specific to polyphenols, and the L-P method had the widest working range but lacked accuracy. The DMAC method was the most specific to flavanols, and the BSA method was not suitable for quantification of smaller flavanols. Quantitative performance of these four methods was evaluated using a broad range of fruit-derived samples. Variation in quantitative results obtained using these four methods was explained by differences in polyphenol and matrix composition of these samples and differences in operating principles of the methods. The reactivity of individual polyphenol compounds (catechin, epicatechin, PC B2, PC pentamer, chlorogenic acid, phloretin, and quercetin) to the polyphenol and flavanol quantification results using Prussian blue (P-B), F-C, DMAC and BSA precipitation methods were also assessed and determined to differ by up to thirteen-fold, depending on the assay. Furthermore, the contribution and interactions of polyphenol compounds (catechin, PC B2, and chlorogenic acid) and potentially interfering compounds likely to be found in fruit and fruit products (ascorbic acid, glucose, and SO2) to the quantitative results of these methods were evaluated using a full factorial design. Significant interactions among polyphenol compounds, and among the interfering compounds were found. The standardized coefficient (β) for all factors and interactions of polyphenol compounds varied from 0.347 to 129, and from near 0 to -46.8 for all factors and interactions of interfering compounds. Our findings indicate that the choice of standards, polyphenol and matrix composition of the sample may cause disparity among the quantitative results of these methods. Amino acids in apple (Malus × domestica Borkh.) juice not only influence the quality of fermented cider through fermentation kinetics but also impact the flavor of the cider through yeast metabolism. Due to recent advances in analytical instrumentation, amino acids profiles in apple juice were determined much faster and more accurately than by previously applied methods. Twenty amino acids were quantified by UPLC-PDA in juices from 13 apple cultivars grown in Virginia. The relative amino acid profile was significantly different among the apple juices evaluated. The total amino acid concentration ranged from 18 mg/L in Blacktwig juice to 57 mg/L in Enterprise juice. L-Asparagine, L-aspartic acid and L-glutamine are the principal amino acids observed in most apple juices. These results will inform future research on yeast metabolism and nitrogen management during cider fermentation. To better disseminate knowledge gained through research to the next generation of food scientists, the effectiveness of new instructional technology—a cellphone-based personal response system—in food science education was evaluated. Students' academic performance was improved by the incorporation of this technology into lectures, and its use was well perceived by the students (easy to use and positively impacted their learning). This finding contributes to the scholarship of teaching and learning in food science by providing useful insight into the potential for application of such tools with improved student engagement and learning outcomes. Advances in food chemistry research will enable the development of value-added food products, and the pedagogical advancement in food science education will better convey new and existing knowledge to students, who will apply this knowledge to promote a safe and nutritious food supply that enhances human health and increases the value of specialty crops.
  • Thumbnail Image
    The Effect of Fungicide Residues and Yeast Assimilable Nitrogen on Fermentation Kinetics and H2S Production during Cider Fermentation
    Boudreau, Thomas F. IV (Virginia Tech, 2016-07-06)
    The Virginia cider industry has grown rapidly in the past decade, and demands research-based recommendations for cider fermentation. This study evaluated relationships between the unique chemistry of apples and production of hydrogen sulfide (H2S) in cider fermentations. Yeast assimilable nitrogen (YAN) concentration and composition and residual fungicides influence H2S production by yeast during fermentation, but these factors have to date only been studied in wine grape fermentations. This study surveyed 12 Virginia-grown apple cultivars and found that the majority were severely deficient in YAN. The effects of three fungicides on cider fermentation were investigated; elemental sulfur, fludioxonil and fenbuconazole. Fenbuconazole adversely impacted fermentation kinetics. Sulfur and fludioxonil marginally impacted fermentation kinetics. Sulfur increased H2S production, but fludioxonil and fenbuconazole did not affect H2S production. There was no difference in fermentation kinetics and H2S between nitrogen sources arginine (approximating grape), asparagine (approximating apple) and ammonium (YAN supplement). Supplementation with methionine resulted in increased fermentation rate and decreased H2S production. The detrimental effects of fenbuconazole and beneficial effects of methionine were diminished with increasing total YAN. Contrary to previous findings, the most H2S was formed at 153 mg/L YAN which is above the generally recommended minimum to prevent H2S formation. These results indicate that apple juice chemistry may influence yeast metabolism during cider fermentation, in ways that have not been previously studied in grape fermentation. Our findings indicate the need for and contribute to the development of targeted fermentation management practices for cidermaking.
  • Thumbnail Image
    The Effect of Supplemental Grape Seed Extract on Pig Growth Performance and Body Composition During Heat Stress
    Smithson, Andrew Todd (Virginia Tech, 2016-07-08)
    Prolonged exposure to high ambient temperature without cooling causes heat stress (HS) resulting in altered growth, body composition and metabolic dysfunction in pigs. Grape seed extract (GSE) has been shown to reduce inflammation, and improve glucose transport and metabolism. Thus, GSE may be an effective supplement to combat the consequences of heat stress; however this possibility has not been evaluated in a large animal model. The objective of the current study was to examine the effect of GSE supplementation on pig performance and body composition during HS. Twenty-four female pigs (62.3± 8 kg BW) were randomly assigned to a 2X2 factorial experiment; thermal neutral (TN; 21-22°C) or heat stress conditions (HS; 33-34°C) for 7 days and fed either a control or a GSE supplemented diet (12mg/kg body weight). Body temperature (TB), respiration rate (RR) and feed intake (FI) were measured daily. Body composition was measured by dual-energy X-ray absorptiometry (DXA). Respiration rate and TB increased in the HS control group compared to the TN control group (p<0.05), however GSE did not alter these parameters compared to control for the duration of the 7 day period. HS decreased FI (P < 0.05). Fasting blood glucose concentrations were approximately 1.5-fold greater in the control diet compared to their GSE supplemented counterpart (p=0.067) on day 6 of the HS period, but did not differ between groups at the end of day 7 of HS. Body composition analysis indicated bone mineral density, bone mineral content, and percent change of fat remain unchanged between treatment groups. Percent change in weight was significantly reduced in HS. Lean tissue accretion was 45% greater in TN compared to HS groups (p<0.05). Endotoxin concentrations were approximately 2-fold lower in the HS-GSE group compared to the control (P=0.083). Grape seed extract supplementation does not appear to alter pig growth performance or body composition, but does appear to delay the onset of reduced feed intake by 1 day, reduce intestinal permeability, and improve insulin sensitivity during additional stress.
  • Thumbnail Image
    Effects of Hydroxycinnamates and Exogenous Yeast Assimilable Nitrogen on Cider Aroma and Fermentation Performance
    Cairns, Paulette Anne (Virginia Tech, 2019-07-08)
    Heritage apple cultivars for cider-making are often distinguished by a high concentration of tannins (phenolic compounds), and/or acid. The phenolic content of some cider apples far exceeds that of white wine, however most cider fermentation practices are directly taken from white winemaking, not accounting for effects of high concentrations of phenolic compounds on yeast fermentation. The objective of this study was to determine the impact of ferulic acid, p-coumaric acid, and chlorogenic acid—at concentrations reported in apples—and their interactions with yeast assimilable nitrogen (YAN) on fermentation kinetics and cider aroma. Our hypothesis was that the phenolic compounds present in high-tannin cider apples would negatively impact fermentation kinetics, but not alter the aroma, and that added YAN would reduce these effects. Ferulic acid negatively affected fermentation performance (p < 0.05), but p-coumaric acid and chlorogenic acid did not. p-Coumaric acid led to the greatest changes in cider aroma. Differences were also detected for different concentrations of ferulic acid. Chlorogenic acid did not affect aroma. Yeast strain influenced fermentation performance and cider aroma. Finally, addition of exogenous YAN improved fermentation performance for the low concentration ferulic acid condition, but not for the high concentration. Adding YAN also changed cider aroma in the presence of p-coumaric acid.
  • Thumbnail Image
    Evaluation of cocoa (Theobroma cacao) bean processing strategies to enhance alpha-glucosidase inhibitory activity of dietary cocoa
    Racine, Kathryn Claire (Virginia Tech, 2019-06-18)
    Cocoa beans (Theobroma cacao) are a highly concentrated source of dietary flavanols- bioactive compounds associated with the health protective properties of cocoa. Cocoa beans undergo processing steps, such as fermentation, roasting, winnowing, grinding, pressing, etc., to produce a final product with specific desirable sensory attributes. It is well established that these processing steps, specifically fermentation and roasting, result in dramatic degradation of cocoa's native flavanols, but it is possible that these processing steps may generate compounds with novel activities, potentially preserving or enhancing bioactivity. Raw unfermented cocoa beans were processed by way of a partial factorial approach to produce cocoa powders from the same batch of raw beans using various combinations of fermentation [unfermented, cool fermented (maximum 46°C), hot fermented (maximum 60°C))] and roasting [unroasted, cool roasted (120°C), hot roasted (170°C)]. To simulate cocoa fermentation in a highly controlled environment, a pilot-scale fermentation model system was employed to eliminate many external unknowns and ensure that the differences between our cocoa powders were due to our various treatments, rather than unknown factors occurring during fermentation and roasting. Low and high molecular weight fractions (8-10 kDa cutoff) were produced from cocoa powder extracts (CPE) of each treatment to quantify Maillard reaction products (MRP). A HILIC-UPLC MS/MS method was developed to more efficiently and sensitively quantify cocoa flavanols with high degrees of polymerization (DP) produced during processing. Overall, cocoa processing significantly (p<0.05) decreased the total phenolic and total flavanol concentrations of CPEs. Hot roasting had the greatest impact on native flavanol degradation yet produced CPEs with the highest mean degree of polymerization (mDP). All CPEs dose-dependently inhibited α-glucosidase enzyme activity, with cool fermented/cool roasted cocoa powder exhibiting the best inhibition (IC50 of 62.2 µg/mL). Increasing flavanol mDP was correlated with decreasing IC50 values, suggesting that the complex flavanols produced during processing enhance cocoa's bioactivity (or their production is associated with other products that enhance bioactivity). Alternatively, high molecular weight CPE fractions were correlated with increasing IC50 values, suggesting that MRPs interfere with enzyme inhibition or are associated with other products (polyphenols, macronutrients, etc.) that interfere with enzyme inhibition. Overall, the data presented within this work indicate that the components of processed cocoa powders are promising inhibitors of α-glucosidase, despite a significant reduction in native flavanol composition induced by processing, and moreover that fermentation and roasting conditions can positively influence the bioactivity of cocoa despite losses of native flavanols.
  • Thumbnail Image
    Evaluation of Nitrogen Management Schemes in Cover Cropped Vineyards
    Moss, James Russell (Virginia Tech, 2016-06-06)
    Vineyards in the Eastern United States are often prone to excessive vegetative growth. In order to suppress excessive vine vigor, many viticulturists have employed cover cropping strategies. Cover crops provide a myriad of agronomic benefits, however they are known to compete with the vine for water and nutrients. Due to the widespread use of cover crops in Eastern vineyards, many vineyards experience nitrogen (N) deficiencies in both the vegetative vine tissue and yeast assimilable nitrogen (YAN) in the juice. Soil applications of calcium nitrate and foliar applications of urea were assessed as a means of vineyard N amelioration at cover cropped sites comprised of Petit Manseng and Sauvignon blanc (Vitis vinifera L.). Perennial White and Crimson clover cover crops and foliar urea applications were also used in a Vidal blanc (Vitis spp.) vineyard. Treatments were imposed in the Sauvignon blanc vineyard for five years. The Petit Manseng and Vidal blanc vineyards were subjected to treatments for two years. Soil-applied N at bloom was most effective at increasing leaf petiole N at véraison, season-long chlorophyll content index (CCI), vine capacity and fruit yield. Fruit yield was increased due to more berries per cluster and greater berry weights. Increased rates of soil-applied N decreased the fruit weight:pruning weight ratio. Foliar-applied N after fruit set was most effective at increasing berry YAN. While most of the measured amino acids in fruit increased in concentration with the application of either soil or foliar N, foliar applications were more effective at increasing fruit amino acids. Clover cover crops offered little to no benefit as a N source in the two-year period of evaluation. None of the N management schemes negatively impacted canopy density, fruit zone light interception, or botrytis bunch rot incidence. The combination of both a soil-applied and foliar-applied N fertilizer may be the most effective means to increase both vine capacity and YAN in vineyards where vineyard floor cover crops are compromising vine N status.