Interest in grape juice has risen as the public becomes more aware of natural foods and the specific evidence of healthful benefits of grapes. Among major preharvest conditions that influence quality of grape juice are climate, soil, cultivar, vineyard management, and maturity. Each of these factors exerts its own influence, but complex interactions among these factors must be recognized. For mechanically harvested juice grapes, cultivar takes on special importance to quality and yield as do the production system, harvest machines, postharvest handling systems, and processing method. Grape juice composition has been extensively studied, and production and processing methods have improved over the years. The following discussion deals with developments in grape juice production.
Justin R. Morris
Justin R. Morris
The moderate consumption of red wine, grapes, raisins, and grape juice has a demonstrably positive effect on human health. Scientifically conducted surveys have shown that the effects of moderate intake of red wine reduces circulatory disease. Legislative efforts on labeling red wine to show the scientific evidence of this statement are receiving favorable attention. The antioxidant resveratrol, present in the skins of the grape in any of its various forms, is believed to be the agent primarily responsible for the healthful benefits demonstrated. It has been shown to affect lipid metabolism in higher mammals. Studies of resveratrol content in a variety of wine grapes are being performed at the Univ. of Arkansas, as well as at other institutions. Red wine (in contrast to white wine and other alcoholic beverages) reduces clotting ability and increases levels of high-density lipoproteins (“good” cholesterol), which diminishes the risk of coronary problems. Grape skin extract, red wines, and red juice appear to enhance the ability of blood vessels to resist vasoconstriction and to contribute to antithrombotic activity. In laboratory tests, several known antioxidants in wine out-performed vitamin E, the current best-known dietary antioxidant.
Justin R. Morris
A major research thrust of the University of Arkansas Enology and Viticulture Program for the past 37 years has been the development of a total vineyard mechanization system. This new system allows the mechanization of almost all practices in vineyard operations, including dormant and summer pruning, leaf removal, shoot and fruit thinning, canopy management, and harvesting while fruit quality is maintained or enhanced. Research efforts aimed to accomplish these tasks on the 12 major trellising systems used throughout the industry and to derive plans for the sequencing and timing of operations on each of the trellis systems. In 2002, the University of Arkansas patented the Morris-Oldridge Vineyard Mechanization System (M-O System). OXBO International Corp., Clear Lake, WI, purchased the patent and market M-O System components under the name Korvan™ Vineyard System. The objective of this study was to evaluate the effectiveness of mechanized (machine-farmed) pruning, shoot thinning, and fruit thinning using the M-O System vs. traditional methods of canopy management using hand labor (hand-farmed) in a commercial Vitis vinifera vineyard in the central coast region of California. V. vinifera cultivars evaluated included Chardonnay, Sauvignon blanc, and Syrah trellised on a lyre system and Merlot, Zinfandel, and Sangiovese trellised on a vertical shoot-positioned (VSP) system. Yield, fruit growth, fruit composition, wine quality, wine sensory attributes, and economics of mechanization were evaluated on machine- and hand-farmed grapes. Mechanized studies were initiated at French Camp Vineyards, Santa Margarita, CA, in 2002. French Camp Vineyards used a balanced cropping concept which incorporated three operations: 1) machine dormant pruning, 2) machine shoot thinning, and 3) machine fruit thinning. Results of research from 2002 to 2005 showed that yield and quality characteristics of machine-farmed grapes were not statistically different from those of hand-farmed grapes for the V. vinifera cultivars in this study. Wines from each cultivar and treatment were produced at a commercial winery and after appropriate aging, were sensory-evaluated by a professional wine analysis service. Few sensory differences were found between wines from the two farming systems. Further objective analyses of the wine components showed no commercially practical differences. In 2006, cost estimates were derived for the three vineyard activities necessary to achieve balanced cropping. Use of machine farming for balanced cropping operations resulted in savings over hand farming of 45% on the lyre trellis, 49% on the VSP system, and 62% on the quadrilateral trellis for the operations studied. Studies of mechanization of vineyard activities using the M-O System to achieve balanced cropping have shown that grapes and their wines were equivalent to those obtained using hand labor for these operations with the added benefit of cost savings for the operations evaluated.
Justin R. Morris
Mechanization of harvesting, pruning, and other cultural operations on many small fruit crops for the processing market has occurred in response to the scarcity and expense of hand labor. Scientists at the Arkansas Agricultural Experiment Station and other experiment stations in the United States and throughout the world have developed new cultural and fruit-handling systems and have determined the effects of these systems on fruit yield and quality. This research has resulted in the development of prototype and commercial machinery as well as production and handling systems that have assisted in mechanization systems for brambles, strawberries (Fragaria×ananassa Duch.), and grapes (Vitis sp.). Much of this body of work is in commercial use and much is simply available, awaiting circumstances that will be beneficial to implementation.
Justin R. Morris and Pamela L. Brady
Janice M. Blevins and Justin R. Morris
There has been a nationwide explosion of interest in consumption of red wine following a “60 Minutes” television segment entitled “The French Paradox.” The paradox was due to the fact the French consume more fat, smoke more, and exercise less than Americans and still have fewer heart attacks. A study of 12,000 male British doctors showed that moderate drinkers had the lowest death rates and the lowest vascular death rates compared to nondrinkers or heavy drinkers. The consumption of wine has been shown to provide healthful benefits, such as reducing cholesterol and decreasing cardiovascular disease. A comprehensive literature review of the latest scientific information on this subject is presented in this review.
J.N. Moore, John R. Clark and Justin R. Morris
The impending release of a new blackberry cultivar and a new grape cultivar by the University of Arkansas Agricultural Experiment station will be discussed. The blackberry, tested as A-1536, is an erect, thornless type ripening two weeks before 'Navaho'. It produces very firm, highly flavored fruit similar to 'Navaho'. The grape, tested as A-1335, is a blue-seeded juice grape with good adaptation to areas with high summer temperatures where 'Concord' does not ripen evenly. Fresh fruit and processed juice quality has been rated equal to or better than 'Concord' juice for quality attributes.
James N. Moore, Justin R. Morris and John R. Clark
John R. Clark, James N. Moore, Justin R. Morris and Renee Threlfall
Teresa L. Walker, Justin R. Morris, Renee T. Threlfall, Gary L. Main, Olusola Lamikanra and Stephen Leong
Muscadine grapes (Vitis rotundifolia Michx.), native to the southeastern United States, have a distinct flavor, and grocers are interested in marketing them as table grapes. Two studies using 'Fry' muscadines were conducted to assist the muscadine industry in providing quality table grapes. Study 1 (1998 and 1999) evaluated density sorting and relationships between maturity, color, soluble solids, firmness, shelf life, and sensory evaluation of grapes. Study 2 (1998) determined the effect of storage on quality attributes of different maturities of grapes and evaluated use of polyethylene bags to extend their storage. Density separation successfully sorted grapes by maturity. Muscadine berry color may allow for visual or electronic sorting to eliminate immature fruit. Sensory panelists could distinguish differences in maturities for all sensory attributes. In 1999 maturities 3 and 4 (≈24-33 soluble solids: acid ratio) were preferred overall by panelists. As maturity increased, soluble solids and pH increased, and acidity decreased. Firmness decreased as maturity and storage at 2 °C increased. Percent decay increased with maturity and storage time. Grapes stored in polyethylene bags had reduced decay. A chart developed from the 1999 data related berry color to soluble solids: acid ratio, soluble solids, tartaric acid, and pH. Data from these studies can be used by industry to establish harvest parameters and enhance marketability of 'Fry' muscadine grapes.