Florida Muscadine Grape Juice: Processing and Evaluation Compared to Commercial Grape Beverages R
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Proc. Fla. State Hort. Soc. 92:195-197. 1979. FLORIDA MUSCADINE GRAPE JUICE: PROCESSING AND EVALUATION COMPARED TO COMMERCIAL GRAPE BEVERAGES R. P. Bates and D. Gursky through the crushing section of a cider crusher-press. The Food Science and Human Nutrition Department, IFAS, crushed grapes were then processed by one of three methods: University of Florida, (1) pressed immediately at ambient temperature (about Gainesville, FL 32611 25°C), (2) left at 10°C or 18°C for various time periods prior to pressing or (3) hot-pressed by heating to 60° C with Abstract. Canned grape juice was produced from a 0.72 g Spark-L® pectic enzyme (Miles Lab, Inc.) per kg. number of Florida-grown muscadines (Vitis rotundifolia) and crush and held for 30 minutes. compared with 19 commercial grape beverage products. Pressing consisted of a rack and cloth press pressure of Eleven of the commercial products were rated "good" while about 200 psi applied for 15 minutes. The freshly pressed only 2 of the 12 Muscadine juices received comparable juices were cold stabilized by slow freezing in sealed, plastic scores. The major defects in the commercial juices were poor buckets at — 18°C and subsequent slow thawing at 2°C. The color and weak or atypical grape flavor. The principal thawed juice was removed by passing the juice through a problem in Muscadine juice was low acidity, prompted by 100-mesh Sweco vibrating screen. cold stabilization (detartration) which increased the B/A Juice pasteurization and bottling were accomplished by ratio to >35. When this defect was corrected by addition passing the juice through a stainless steel tube coil im of citric acid, the resulting blends were more acceptable. mersed in boiling water. Flow rate was adjusted so that Addition of grapefruit juice improved flavor, but color was the juice issued from the tube at about 95°C and was filled poor and defects apparent, especially in the white musca directly into clean pint or quart canning jars leaving a one dine juices. With attention to juice clarification and brix/ cm. headspace. Two-piece lids were attached, the jars were acid adjustment, acceptable commercial quality grape juice inverted for three minutes and cooled first in warm (60° C) can be produced from Welder and Noble Muscadines. and then in cool (22°C) tap water. Canned juices were stored at ambient temperature (25°C) until analyzed. The technical, production, marketing and distribution In several experiments, citric acid and grapefruit juice capabilities of the citrus industry are resources not readily were used to adjust high brix/acid (B/A) ratios of the available to other Southeastern states and could catalyze muscadine juices. A quantity of low ratio (7.6) 60° con significant expansion in grape acreage in Florida. However, centrated grapefruit obtained from the IFAS Lake Alfred it must first be shown that a good quality juice can be Agricultural Research and Education Center was reconsti economically produced from local muscadines. tuted to 12° Brix prior to acid adjustment. Early work with muscadine grape juice in Georgia over came the problem of high astringency in older varieties (15). Analyses Recent juice processing investigations with improved varie ties are also encouraging (7). Much of the work with musca All commercial grape beverages were evaluated as opened dine wine where juice extraction is often the initial step or reconstituted according to package directions in both suggests that good quality juice can be derived from many frozen concentrates and dry mixes. Soluble solids (Brix) breeding lines and cultivars being evaluated for their wine were measured by refractometer, pH by glass electrode and potential. acidity by titration of 10 ml to a pH 8.2 endpoint with 0.1 The purpose of this study was to evaluate the range N sodium hydroxide. Acidity was reported as g. tartaric and quality of commercial grape beverage products avail acid/100 ml. able on the market and compare them with juices prepared Sensory evaluation consisted of presenting individual from Florida muscadines. grape beverage samples (chilled to about 10°C) to a panel of five judges familiar with grape products. Judges were Experimental asked to rate the products using the USDA scale for canned grape juice (Table 1). Four samples were presented at each Commercial Grape Beverages A comprehensive survey of all commercial grape beverage Table 1. Scores of Standards for Grades of Canned Grape Juice. products available in. the Gainesville, Florida area was conducted. During a three-week period, samples of every Quality Classification brand of juices, drinks, concentrates and dry mixes identi reasonably fied as "grape" were purchased from local food stores and Factors good good substandard stored at 2°C, except for frozen concentrates stored at 18°C Color 34-40 28-33 0-27 Absence of Defects 17-20 14-16 0-13 Muscadine Juice Preparation and Processing Flavor 34-40 28-33 0-27 Grapes were obtained from experimental plantings at Total 85-100 70-82 67 the IFAS Leesburg Agricultural Research Center or com mercial vineyards near Gainesville during the 1978 harvest. Fruit were either processed the same day or picked and daily session with grape juices being evaluated first, followed stored at 2°C for one to three days. Processing consisted of by the juice drinks, drinks, frozen concentrates and dry removing leaves and harvest debris and passing the berries mixes. Experimental muscadine juices were then evaluated separately but according to the same procedure used for the Florida Agricultural Experiment Station Journal Series No. 2091. commercial juices. Proc. Fla. State Hort. Soc. 92: 1979. 195 Results and Discussion Similar analyses and sensory evaluation of muscadine juices are reported in Table 3. In contrast to the com There was a surprising number of commercial grape mercial juices where defects were minor, practically all ex beverage products in Gainesville markets. Nineteen products perimental juices were severely down-rated due to cloudi representing twelve distinct brands were collected and evalu ness. This could have been remedied by filtration. ated. As shown in Table 2, the composition of these bever Most white muscadine juices were down-graded because ages likewise covered a broad range. of the dark color inherent in the use of hull treatments and The most dramatic difference was in price. Juices the fact that sulfur dioxide was not employed, a standard ranged from 10 to 15 cents/100 ml, frozen concentrate was practice in commercial white juice but not used here in the 7 cents/100 ml and dry mixes were 4 cents/100 ml (reconsti interest of treatment uniformity. tuted basis). Among purple juices, subtle differences in The flavor defects in white and red muscadine juices purple color were noted, but the color and flavor of the was attributed to high B/A ratios ranging from 34 to 56 so most expensive juice was comparable with that of compet that the samples were described as "bland", "watery" and ing brands purchased at almost half the cost. B/A ratios of "too sweet". The lack of tartness was due to detartration purple juices ranged from 18 to 24 which is somewhat lower which had occurred in most of the juices during freezing than the 25 to 35 range found to be optimum in musca and thawing and caused decreases in acidity ranging from dine juices (12). The white juice, red juice and purple 0.2 to 0.4%. In addition, Welder and Southland grapes frozen concentrate were about 35 brix while drinks and dry were harvested late in the season and, when pressed, gave mixes were between 33 and 50 in B/A ratios. Grape drinks unusually high brix juices which further increased B/A were less expensive but were rated considerably lower than ratios. White juices left on the hulls a short time before the 100% juice products. They were usually described as pressing and hot-pressed red juices had the most acceptable "overly-sweet" and "lacking tartness" and had B/A ratios flavor. of greater than 33. Total scores ranged from 77 to 87 with whites averaging On the USDA 100-point scoring system, all commercial 78.6 and reds 83.2. The red experimental juices were com products were practically free from defects, but some parable to juice drinks and inferior to commercial juices (primarily dry mixes) were down-rated in color and/or while the white experimental juices were poorer than all flavor. Total scores for commercial juices ranged from about commercial juices and drinks. 72 to 95 with average ratings of 88.8 for juices (including An attempt at overcoming the high B/A ratios of three the frozen concentrate), 84.8 for drinks and 75.9 for dry red and three white muscadine juices was made by blend mixes. ing with grapefruit juice or adding citric acid. These ad The major difference between the purple, canned juice justments corrected B/A ratios and improved most flavor "and its reconstituted frozen concentrate was in price. The scores, but the grapefruit imparted more cloud and ad latter was half the cost per 100 mis. and had slightly better versely influenced clefect and color scores. The net result color, but its flavor was less acceptable. Red commercial was total scores lower with grapefruit and higher with juice received a low color score (perhaps due to expectations citric acid addition. of a purple-colored grape juice), but its flavor was considered Even discounting defects (which could have been superior to that of the purple juice. White juice had better avoided by filtering the juice and blends) and given the color and flavor than purple, and it received the highest benefit of B/A ratio adjustments, none of the experimental total score.