title: Influence of pressing method on juice stilbene content in muscadine and bunch grapes.
abstract: 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.
authors.affiliation: Louisiana Dept. of Agriculture and Forestry, Baton Rouge, LA 70821, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Leblanc
authors.forename: C E
authors.initials: CE
authors.lastname: Johnson
authors.forename: P W
authors.initials: PW
authors.lastname: Wilson
mesh_terms: D001628:Beverages / Q000032:analysis*; D003080:Cold Temperature; D005511:Food Handling / Q000379:methods*; D005615:Freezing; D005638:Fruit / Q000737:chemistry*; D005960:Glucosides / Q000032:analysis; D006358:Hot Temperature; D011096:Polygalacturonase / Q000378:metabolism; D000077185:Resveratrol; D013267:Stilbenes / Q000032:analysis*; D027843:Vitis / Q000737:chemistry*
chemical_list: D005960:Glucosides; D013267:Stilbenes; D011096:Polygalacturonase; D000077185:Resveratrol; C058229:polydatin