Paul W. Wilson

Relationship between Hunter Color Values and β-Carotene Contents in White-Fleshed African Sweetpotatoes (Ipomoea batatas Lam)

White-fleshed sweetpotatoes (Ipomoea batatas (L) Lam) are a major food crop in Uganda. This study was done to evaluate carotenoid content in sweetpotatoes and to relate the color of the sweetpotatoes to the β-carotene present. A Hunter Color Tristimulus Meter was used to determine the color and the β-carotene was determined by reverse-phase HPLC. Regression analysis was carried out on the color values L, a, b, b/a and tan-1 b/a to determine which color value could be used to express the content of β-carotene in white-fleshed sweetpotatoes. The ‘b’ color value appeared to be the best estimation for correlation at 0·74 in this study for raw roots and 0·09 for puree. The ‘a’ value was 0·39 for raw roots and 0·16 for puree, L was -0·74 for raw roots and -0·45 for puree.

Influence of Pressing Method on Juice Stilbene Content in Muscadine and Bunch Grapes

Juice stilbene contents of 2 muscadine (Vitis rotundifolia) cultivars, Noble and Carlos, and 2 bunch grape (Vitis labrusca) cultivars, Mid South and Miss Blanc were evaluated after crushing and pressing. Four commercial pressing methods were used to produce juice: (1) cold press of fresh berries (CP); (2) hot press of fresh berries (HP); (3) cold press of frozen and thawed berries (FCP); and (4) cold press of pectolytic enzyme treated berries (ECP). Free run juice (FRJ) from the crusher without pressing was also tested. An HPLC with a UV detector was used to verify the presence and quantity of resveratrol, piceid, and their isomers. For the muscadine juices, total stilbenes were greater for HP and FCP than for FRJ and CP treatments. Trans-resveratrol was only detected in HP juices of the muscadines at levels near the detection limits. The bunch grape cultivars behaved similar to the muscadines in the processing treatments. HP juice had the greatest total stilbene levels and was significantly greater than FRJ, CP, and FCP. Total stilbene levels in juices from the 2 bunch grape cultivars, were higher (up to 5 times greater depending on pressing method) than for the muscadine grape cultivars. Total stilbene levels in muscadine juices treated with pectinase before pressing (ECP) were similar to those of the FCP samples. Juice from FCP and ECP treated Noble muscadine had total stilbene levels greater than FRJ and CP but less than HP levels. Juices from HP-, ECP-, and FCP-treated Carlos muscadine had total stilbene levels greater than for FRJ and CP juices.

Stilbene Levels in the Tissue and Juice of Muscadine Grapes (Vitis rotundifolia Michx.)

Abstract Stilbenes are secondary metabolites of a class of non-flavanoid phenolics found in certain species of Vitis. This class of compounds includes resveratrol and a resveratrol glucoside called piceid that exists in trans and cis forms. This study was undertaken to determine the cis and trans forms of both resveratrol and piceid in the skin, pulp, seeds, and juice of nine cultivars of muscadine grapes and three cultivars of Vitis labruscana. Juice samples of the muscadine cultivars ‘Fry’, ‘Hunt’, ‘Magnolia’, ‘Watergate’, ‘Carlos’, ‘Noble’, and ‘Sweet Jenny’, and the V. labruscana cultivars ‘Albermarle’, ‘Miss Blanc’, ‘MidSouth’ and ‘Miss Blue’ were harvested at the full ripe stage and divided into two sub-samples. One subsample was used to extract juice and the other was divided into skins, pulp, and seeds. Sample analysis was performed using HPLC with a UV detector. Sample chromatagrams were compared with those of known standards for quantification. ‘Carlos’ and ‘Magnolia’ had the greatest total stilbene concentration in skin tissue and had bronze skin containing higher concentrations of total stilbenes than any of the black-skinned cultivars tested. Only one bronze skin cultivar, ‘Sweet Jenny’, had lower stilbenes than the dark skin cultivars. Piceid, cis piceid and resveratrol were found in the skins of all cultivars. ‘Carlos’ ‘Magnolia’, ‘Fry’ and ‘Albermarle’ muscadines contained cis resveratrol in the skins of the fruit. ‘Watergate’ was the only cultivar in which resveratrol was detected in seed tissue. ‘Sweet Jenny’ had the highest levels of cis piceid in seed tissue. ‘Albermarle’, ‘Carlos’ and ‘Sweet Jenny’ had significantly greater levels of cis picied in pulp tissue than all other cultivars.

Consumer Acceptance of Mayhaw (Crataegus opaca Hook, and Arn.) Juice Blended with Muscadine Grape (Vitis rotundifolia Michx.) Juice

Abstract Fruit juices are among the top 10 products occupying grocery store shelf space. They are also one of the top five consumption patterns of fruits and vegetables. There is a strong potential for growth in blended juices and juice-based beverages. A study was conducted to evaluate the potential for mayhaw and muscadine juices to compete in this growing market. Mayhaws and muscadines are well utilized in jams, jellies, and syrups. Five juice-blend ratios were tested for juice quality, juice-blend compatibility, and consumer preference. Pasteurized samples of mayhaw and muscadine juice were blended 70/30, 60/40, and 50/50. Juice was ambient temperature when tested. Color, percent soluble solids, and sugar/acid ratio were evaluated. Juice blends of 70, and 60% muscadine received the lowest color preference values among panelists. Forty to seventy percent mayhaw juice received the highest color preference scores. A blend of 60/40 muscadine/mayhaw was most preferred among panelists for overall taste. When consumers were asked to compare a commercial blend of cranberry/apple juice, with a 60/40 or 40/60 blend, the muscadine/mayhaw combination was most preferred.

Characterization of Juice Extraction Methods Utilizing Fresh Mayhaw (Crataegus opaca Hook.) Fruit

ABSTRACT Six juice extraction methods for mayhaw (Crataegus opaca Hook. and Arn.) cultivar Texas Star were evaluated for percent juice yield, pH, °Brix (soluble solids), titratable acidity (TA), sugar/acid ratio, sugar and organic acid contents, and color of extracted juices from fresh fruit. Methods studied were steam extraction using whole fruit with added pulp juice (SEP) or without added pulp juice (SE), cold-press extraction using whole fruit (CPE) or finely ground fruit (CPEG), hot-press extraction using finely macerated fruit pulp (HPEG), and hot-press extraction in combination with a pectolytic enzyme pretreatment (ENZ). Juice quality was determined by HPLC analysis of sugar and individual organic acid. Juice quality and extraction efficacy were significantly (P ≤ 0.05) affected by extraction. Steam extraction using whole fruit with added pulp juice produced the highest yield (70.3%). Fructose and glucose were predominant sugars and malic was the predominant acid in all extracted juices. SEP produced juice with lowest amount of total sugars. TA and pH of all extracted juices were significantly (P ≤ 0.05) affected by the extraction methods. The lowest TA value was for SE at 0.51% and highest for HPEG at 1.28%.The lowest pH values were for CPE at 2.97 and highest pH value at 1.13 for SE. L* values (lightness) of fresh juices was significantly (P ≤ 0.05) affected by extraction method. Cold extraction methods yielded juices with more intense redness and yellowness (a*  =  5.2, b*  =  1.92, chroma  =  5.5, hue angle  = 19.8) than did steam extraction.

Use of a Commercial Pectolytic Enzyme to Extract Juice from Frozen Mayhaw (Crataegus opaca Hook.) Fruit

ABSTRACT The efficacy of a commercial pectinase enzyme preparation was evaluated for juice yield and quality of mayhaw (Creategus opaca) fruit pulp. The use of pectinase in the extraction procedure increased juice color, reduced juice browning—assayed as absorption at 420 nm enhanced color density and increased percent soluble solids. Yield of mayhaw fruit juice significantly (P ≤ 0.05) improved with increasing concentrations of pectinase enzyme from 0.2% to 6.4%. Juice yield of the untreated controls was about 64% (w/w) as compared to yields of 77.2-80.4% from pectinase-treated fruit macerate. Mean soluble solids content of pectinase treated mayhaw fruit juice ranged from 6.6 to 10.4 total Brix (23.4°C), soluble solids content of the untreated mayhaw juice was 6.5%. A significant increase (P ≤ 0.05) in the efficacy of pectinase occurred at a holding temperature of 32°C and 0.20 (% w/w). Enzymatic concentration levels ≥ 0.20% w/w and a reaction temperature of 2°C for 24 hours, treatment effects observed on juice yield, percent soluble solids and CIE* color were similar (P ≤ 0.05).

Comparison of Juice Extraction Methods from Fresh and Frozen Mayhaw (Crataegus opacaHook.) Fruit

ABSTRACT The highest juice yields were obtained from a combined interaction of temperature, maceration, application of pectolytic enzyme, and previously frozen fruit. Freezing mayhaw fruit prior to juice extraction increased juice yield regardless of the method used in extraction. The average juice yield obtained from previously frozen fruit was 157% higher than when using fresh fruit. Maceration of fruit plus the application of heat to the fruit pulp prior to juice expression had a significant influence in juice extraction efficacy for both fresh and frozen fruit. When heat was applied to fruit pulp prior to expression, juice yields increased from 31.4% for cold press extraction and 63.5% for hot press extraction. Application of a pectolytic enzyme to preheated fruit pulp increased total soluble solids (TSS) in extracted juice by 15% when utilizing frozen fruit compared to hot-press extraction without enzymes yield of 6.6%. There was no significant difference in TSS recovered by either fresh or frozen cold press methods without enzymes. All steam extraction methods utilizing fresh fruit had a lower percent recovery of total acid (TA) than when a pectolytic enzyme was added to fresh fruit before extraction. There were no significant differences in juice pH regardless of whether fresh or frozen fruit were used. Recovery of both TSS and fructose was significantly increased when pectolytic enzyme was added to fresh fruit. The lowest recovery of fructose was from steam extraction for both fresh and frozen.