Showing papers in "American Journal of Enology and Viticulture in 1977"

Total Phenol Analysis: Automation and Comparison with Manual Methods

Abstract: A fully automated-continuous flow 40-sample/ hour procedure was adapted from the Singleton-Rossi method of analysis for total phenols in wine and other plant extracts. It was compared with small-volume manual and semiautomated versions of this analysis. The agreement in mg of gallic acid equivalent phenol (GAE) per liter among a series of dry wines was excellent by all three procedures. The coefficients of variation in replicate analyses averaged 5.8% for the manual, 6.2% for the semi-automated and 2.2% for the automated procedure. This greater reproducibility, plus savings of about 70% in labor and up to 40% in reagents, makes the automated procedure attractive for laboratories doing enough total phenol analyses to recoup the cost of the automating equipment. For continuous flow, color development with the Folin-Ciocalteu reagent in alkaline solution must be hastened by heating compared to slower room temperature development for the manual methods. Heating of sugar-containing samples in the alkaline solution gives interference presumably from endiol formation. Examples are given of corrections which were used successfully to estimate the true phenol content of sweet wines.

Influence of Temperature, Solar Radiation and Nitrogen on Coloration and Composition of Emperor Grapes

Abstract: Fruit coloration was investigated in Emperor vines grown in pots in sunlit phytotron, lathhouse, and field conditions under various temperature and light regimes in combination with different levels of nitrogen. At day/night temperatures of 37/32°C no anthocyanins were formed in fruits under either high light (HL; 66.5% sunlight) or low light (LL; 9.5% sunlight), whereas at field temperatures (FT; mean daily temperature 20.3°C), considerable anthocyanins formed under HL (100% sun) or LL (8.9% sun). At 37/32°C, soluble solids in fruits did not increase above 12.9° Brix, whereas at FT, 21° Brix was obtained under HL. The inhibition of anthocyanin formation and sugar accumulation in berries at 37/32°C and HL could not be reversed by transferring vines to temperature favorable for anthocyanin synthesis (FT), whereas when vines at 37/32°C and LL were transferred to FT at HL there was rapid accumulation of sugars but only slight formation of anthocyanin. Anthocyanin in berries decreased 59% in 20 days when the vines were transferred from FT-HL to 37/32°C-HL. Anthocyanin and soluble solids were significantly greater (P Fruit color and soluble solids were significantly less (P

Interrelationships of Sugars, Anthocyanins, Total Phenols and Dry Weight in the Skin of Grape Berries during Ripening

Abstract: The relationship between levels of anthocyanins, total phenols and sugars in the skin of ripening grapes ( Vitis vinifera cvs. Shiraz and Cabernet Sauvignon) was studied in the fruit during the period from veraison to maturity. In grapes with a wide range of anthocyanin contents per unit area of skin there was a good correlation between sugar content of the skin and levels of phenolic substances. The closest correlations, e.g. sugar vs. anthocyanin (r = 0.96) and sugar vs. total phenols (r = 0.95), were found in the first five weeks after veraison. There was a poor correlation between berry Brix levels and levels of polyphenolic substances in the skin at all stages of ripening (r = 0.44-0.45). The role of sugars in the regulation of phenolic biosynthesis in ripening grapes is discussed.

Effect of High Temperatures during the Bloom-Set Period on Fruit-Set, Ovule Fertility, and Berry Growth of Several Grape Cultivars

Abstract: To test the effects of high daytime temperatures (35 or 40°C from 11 AM to 7 PM) from two to eight days before bloom until 12 to 18 days after bloom (bloom-set period) on fruit-set, ovule fertility, and berry growth of several Vitis vinifera L. cultivars, three and four years old potted vines were grown in phytotron rooms. Control vines were maintained at day/night temperatures of 25/20°C during the bloom-set period. After bloom-set, vines in all treatments were held at 25/20°C during the remaining period of berry development and ripening. The percentage of berries set was significantly greater (P Temperatures of 32.5 to 40°C from 7 AM to 7 PM during bloom-set gave a significantly (P

Changes in Some Volatile Constituents of Brandy During Aging

Abstract: Several kinds of experimental brandies, both unaged and aged in various types of U.S. and French oak barrels, were vacuum distilled, the components in the distillate were extracted with ether-pentane (2:1), and concentrated to small volume by removal of the solvent for gas chromatographic analyses with a Carbowax 20M column. Quantitative levels were estimated by comparing peak areas with those of an internal standard, 1-octanol. Acetate esters of isoamyl, n -hexyl, and β-phenethyl alcohols decreased during aging in oak barrels. The ethyl esters of the fatty acids, caproic, caprylic and capric, increased during aging while ethyl laurate changed little or slightly decreased. Compounds derived mostly or entirely from oak, furfural, 5-methyl furfural, diethyl succinate and the cis and trans isomers of β-methyl-γ-octalactone (oak lactones -a and -b), were more abundant in brandies aged in U.S. oak than in French oak and lesser amounts of oak-derived compounds were obtained in brandies from reused barrels.

Effects of Controlled Day and Night Temperatures and Nitrogen on Fruit-Set, Ovule Fertility, and Fruit Composition of Several Wine Grape Cultivars

Abstract: Four-year-old vines of Cabernet Sauvignon, Sylvaner, and Zinfandel were grown in phytotron rooms at three different day/night temperature regimes (25°/10°, 25°/20°, and 15°/10°C) during the period from about one week before bloom until veraison. Half of the vines at each temperature treatment received 1.69 g of N (HN) per 20-liter pot, and the other half received no N (ON). The rate of temperature increase or decrease between the daytime maximum and nighttime minimum for each temperature regime was programmed to approximate field conditions in the Soledad and Fresno areas of California during bloomtime. Ovule fertility and number of seeds per berry in vines grown at 25°/10° and 25°/20° were approximately double that of vines held at 15°/10°C, whereas fruit-set did not differ significantly between temperature regimes. Fruit-set, ovule fertility, and number of seeds per berry were significantly less in Cabernet Sauvignon than in the other two cultivars. When data for temperature treatments and cultivars were combined for unfertilized and N-fertilized vines, the HN vines had significantly greater (P<0.01) fruit-set, ovule fertility, seeds/ berry, berry weight, total shoot length, internode length, rate of shoot growth, petiole nitrate level, fruit acidity, and anthocyanin level in berry skins than did ON vines. Fruit maturity and the pH of berry juice did not differ significantly between nitrogen treatments. The level of NO3-N in petiole at bloomtime ranged from 170 to 330 ppm in ON vines and from 1510 to 6880 ppm in HN vines. The level of petiole nitrate in HN vines of each cultivar was usually significantly greater (P<0.05) at 25°/ 10° and 25°/20°C than at 15°/10°C. Chemical and physiological data supported the conclusion that ON vines were nitrogen-deficient. However, the high fruit-set, ovule fertility, and level of soluble solids in fruits of HN vines did not indicate that excess nitrogen existed, even though bloomtime petiole NO3-N levels averaged 3651 ppm, which is generally considered in the excess range for maximum vine yields.

Formation of Hydrogen Sulfide from Elemental Sulfur During Fermentation by Wine Yeast

Abstract: The concentration of hydrogen sulfide formed from elemental sulfur was followed during fermentation by means of an ion electrode specific for sulfide ion. This method allowed hydrogen sulfide to be measured throughout the fermentation and to be measured more precisely than by chemical methods previously used. Hydrogen sulfide was detected in the fermentation only after about half of the sugar had been fermented; the concentration reached the highest value at the end of the fermentation. Generally, the hydrogen sulfide disappeared completely following the completion of fermentation. The concentration of hydrogen sulfide was found to be dependent upon the kind and the amount of elemental sulfur, the oxidation-reduction state of the medium, the ethanol concentration, and the physiological condition of the yeast. Direct contact of the yeast cell with sulfur particles seemed to be necessary. The reduction of the elemental sulfur was apparently a nonenzymatic chemical reaction caused by certain reducing compounds formed in the yeast cell during fermentation.

A New Strain of Leuconostoc Oenos for Induced Malo-Lactic Fermentation in Eastern Wines

Abstract: A bacterium, isolated from a red table wine made in the laboratory from French-hybrid grapes grown in Pennsylvania following a spontaneous malo-lactic fermentation, was characterized as Leuconostoc oenos and was given the strain designation, PSU-1. It was found to be quite similar in most biochemical characteristics to L. oenos ML-34, a commonly studied strain which was isolated from a California wine. ML-34 and PSU-1 were compared for their growth characteristics in a complex laboratory medium modified to simulate some of the conditions which limit the growth of bacteria in wine. It was found that ML-34 always grew as well as or slightly better than PSU-1 with variations in pH, added ethanol, added sulfur dioxide and different incubation temperatures. Two separate experiments were conducted to compare the strains for induced malolactic fermentation by pure culture inoculation into Pennsylvania red table wines. In the first experiment, three wines made from blends of hot-pressed Pennylvania musts were passed through 0.5 µm filters prior to inoculation. PSU-1 induced malo-lactic fermentation in two of these wines within 11.9 and 15.3 weeks following inoculation, while ML-34 failed to induce malo-lactic fermentation within 50 weeks in all three wines. In the second experiment, bacteria were inoculated into three varietal red Pennsylvania wines made using traditional vinification procedures. Two of the three varieties inoculated with PSU-1 completed malo-lactic fermentation considerably faster than identical wines inoculated with ML-34. In the other variety, wines inoculated with both organisms completed malo-lactic fermentation at about the same time which was much faster than the uninoculated control lots. Sensory evaluation of the varietal wines treated identically, except for the bacterial strain inoculated, revealed that no detectable differences existed in the wines.

Deacidification of Eastern Table Wines With Schizosaccharomyces Pombe

Abstract: Wines made from V. labrusca and French hybrid grapes were produced by using pure or mixed cultures of Schizosaccharomyces pombe and Saccharomyces cerevisiae . Wines of the varieties Villard blanc, Vidal 256, Concord, and Catawba fermented by Schiz. pombe were lower in total acidity than wines fermented by Sacch. cerevisiae . The average reduction in total acidity for all Schiz .-fermented wines was approximately 50%. The Schiz. yeast metabolized nearly the entire amount of malic acid, leaving trace amounts or 0.02%. This investigation was also concerned with inoculation of Baco noir and Concord with Schiz. pombe and re-inoculating with Sacch. cerevisiae at one, two, three, four and six days. Loss in total acidity was greatest when the Sacch. inoculation was delayed six days which caused excessive deacidification. Sacch. cerevisiae inoculation at four days appeared to be best in reducing wine acidity to the proper level.

Developments in Malo-Lactic Fermentation of Australian Red Table Wines

Abstract: Control of malo-lactic fermentation in red table wines is one of the most important technical problems in Australian winemaking. These wines are usually higher in pH (3.4-4.3; mean 3.85) than wines of the same type from other countries (reasons are postulated), and malo-lactic fermentation raises pH still further (0.05-0.35 increase), frequently resulting in lower quality, and in serious cases, bacterial spoilage. The most important and frequently the only contribution of malo-lactic fermentation is bacteriological stability of the wine, providing that the fermentation goes to completion. Quality may or may not be impaired, depending on the wine and the climatic area in which the grapes are grown (malolactic fermentation is considered to be desirable in very cool areas), but the fruit and varietal character is frequently lost. The malic acid content of wines which have not undergone malo-lactic fermentation ranges from about 1-1.5 (the minimum level has not been established precisely) to 4 grams per liter. Residual malic acid after malo-lactic fermentation is usually less than 0.1 gram per liter, though some wines contain between 0.1 and 1.0 gram per liter. This indicates that either malo-lactic fermentation has commenced and not gone to completion (as has recently been shown to occur) or that wines with and without malic acid have been blended. Since malo-lactic fermentation can recommence, these wines are still bacteriologically unstable and have to be handled accordingly. Precise enzymatic analysis of malic acid to detect these low levels is now being used in winery laboratories to supplement semi-quantitative paper chromatography. Acidification is practiced, either by acid addition or hydrogen-ion exchange, to adjust pH to within the range 3.5-3.8. If malo-lactic fermentation occurs, the resultant increase in pH is usually corrected. Induction of malo-lactic fermentation by bacterial inoculation with Leuconostoc oenos has only been partly successful and is little used at present. Since malo-lactic fermentation occurs readily in warm areas in wines with high pH values, prevention is difficult. Nevertheless, routine prevention is now being achieved by pH reduction (preferably before the yeast alcoholic fermentation), early clarification and sterile filtration, sulfur dioxide addition, cool storage, and sterile filtration into the bottle. Fumaric acid addition shows promise as a bacterial growth inhibitor, though more winery data are needed. Most winemakers would prefer malo-lactic fermentation not to take place if they can prevent it.

Evaluating Drip, Flood, and Sprinkler Irrigation of Wine Grapes

Abstract: The response of Saint Emilion to drip, flood, and sprinkler irrigation was measured in the southern San Joaquin Valley. The trial began in 1972 after planting, and the extent of plant and soil modifications was monitored through 1974. The principal benefit with drip irrigation was increased efficiency of water use. Drip irrigation used less water while maintaining vine vigor, fruit production, and fruit quality similar to results with sprinkler or flood irrigation. Soil salt levels with sprinkling and flooding were similar but lower than observed with drip irrigation. With drip irrigation, total salts and sodium concentrated on the surface 100 cm from the vine row (drip line) and to a 30-cm depth. Soil-water pressure-head values and hydraulic gradients indicated substantial soil-water flow to the 150-cm depth following both flood and sprinkler irrigation, whereas flow to the 150-cm depth was slight with drip irrigation.

Grapevine Response to Irrigation and Trellis Treatments in the Salinas Valley

Abstract: Four irrigation treatments (nonirrigation, early cut off, early cut back and late cut off) each with three trellis types (2-wire vertical, 1.4 m high; 3-wire vertical, 1.7 m high; and 2-wire vertical, 1.7 m high with a 0.6-m cross-arm were tested to determine effects on the yield and growth of Cabernet Sauvignon and on the composition of the fruit. The split-split-plot experiment was conducted in a low rainfall Mediterranean climate near Soledad in the Salinas Valley of Monterey County, California. The soils were classified by the Soil Conservation Service as a Chualar loam. Topsoil and root depth was uniformly shallow, approximating 50 cm. Irrigations were scheduled primarily on the basis of tensiometer instruments 40 cm deep. Soil suctions in the irrigated plots were maintained between 10-30 cb during the early season until vine growth resulted in uniform canopy density down the vine row with some shoots trailing the ground. Irrigation then was discontinued for the early cut off treatment; soil suctions were allowed to approach or exceed 80 cb for the early cut back treatment before subsequent irrigations in order to retard further shoot growth; but suctions ranging between 10-50 cb were maintained for the late cut off treatment through mid-September. A soil moisture tension of 1-7 bars at harvest was the goal for the last two treatments. Statistical analysis showed significant differences in °Brix, total acidity, pH, yield of both grapes and fruit sugars, cluster numbers and weights, berry weights, bloom-time petiole percentages of Na, K, and Mg, harvest-time must levels of arginine, and pruning weights. The late cut off treatment showed delayed maturity and lower yields than the early cut back treatment. The non irrigated and early cut off treatment did not result in a more favorable sugar, acid and pH balance, and resulted in lower yields than the early cut back treatment. The 2 wire vertical trellis with a cross-arm resulted in higher yields than the other two trellises only for the early cut back and late cut off irrigation treatments receiving pre-harvest irrigations.

The Proteins of Musts

Abstract: A research program aimed at better understanding of protein turbidity in wines studied the protein content and amino acid composition of total fractions of grape musts from 14 varieties. The proteins extracted from the must of Malvasia Istriana were separated by column electrofocusing: eight fractions were obtained at different pH, and amino acid composition was determined for each fraction. The amino acid pattern and pH of the single fractions were highly correlated.

Comparison of Methods of Deacidification of Musts and Wines

Abstract: A problem often encountered in wines made from Washington grapes is a tendency toward an acidity higher than optimum. An investigation was made of several methods of adjusting the acidity and pH of must and wines. Neutralization of wines with K 2 CO 3 and CaCO 3 was studied, and empirical neutralization curves were produced for each deacidifying agent. These curves can be used to predict the final pH and titratable acidity (TA) of the wine when known amounts of K 2 CO 3 or CaCO 3 are added. To use these curves, the pH, TA and tartaric acid content of the initial wine must be known. Neutralization appears best for moderately high-acid low-pH wines. A comparative study was made of deacidification methods on six grape varieties (three whites and three reds). The methods included neutralization of wines with K 2 CO 3 and CaCO 3 ; calcium double-salt deacidification of musts; malic acid fermentation with Schizosaccharomyces pombe in musts and Leuconostoc oenos ML-34 in wines (red only). The calcium double-salt treatment was most effective in reducing TA with minimum pH shift. Sensory analyses indicate that the double-salt method was preferred in red wines and equal to or better than other methods in white wines. Use of L. oenos in red wines was effective in reducing acidity, particularly in high-acid high-pH red wines when tartrate was added back after growth of the organism.

Airborne Microbial Contamination in A Winery Bottling Room

Abstract: A filtration air-sampling method was adapted to determine the extent and kinds of airborne microorganisms in a large winery bottling facility. The frequency and distribution of airborne microorganisms were recorded as a series of concentration gradients around various sites in the bottling room. The sources that contributed the most airborne organisms, and thus most likely to cause wine contamination at bottling, were: the filler, especially the bell rubbers and rubber spacers; the floor-drain gutters; the filter-pad drip tray; and the outside air. Several measures taken to reduce microorganisms in the air were studied for effectiveness. Continuous cleaning of the bell rubbers and rubber spacers nearly eliminated the filler as a source of microorganisms. Also effective was regular sanitizing of wine spills, the filter-pad drip tray, and floor-drain gutters. Air filters decreased the microorganism count by 89%. Positive pressure and air curtains reduced the organisms introduced from air outside of the bottling room. Species of Acetobacter, Lactobacillus, Bacillus, Saccharomyces, Rhodotorula , and Serratia were isolated, and all but the last were found able to grow in California light sweet table wines. Recommendations are made for reducing airborne microorganisms.

Effects of Defoliation, Trellis Height, and Cropping Stress on the Cold Hardiness of Concord Grapevines

Abstract: The cold hardiness of bark and compound buds of culturally stressed Vitis labruscana Bailey 9Concord9 grapevines was investigated in southwestern Michigan. Defoliation, pruning severity, and cluster thinning influenced cane and bud hardiness. The effect of trellis height on cane hardiness was inconclusive, though some increased hardiness was noted for low trellis buds. Complete defoliation by hand in August delayed acclimation in the fall and gave more rapid deacclimation in the spring. Effects of defoliation on cane and bud hardiness were more pronounced during the second year of treatment. Pruning severity was the most important factor influencing cane and bud hardiness in undefoliated plants. Field observations emphasized the importance to greater hardiness of balanced pruning at 30 + 10 severity as opposed to (60 + 10) pruning. Cluster thinning increased hardiness levels that had been depressed by 60 + 10 pruning, particularly when vines were defoliated. The greater sensitivity of underpruned vines seemed to be a result of the overproduction of fruit. With most treatments, the tertiary bud was as hardy as the secondary bud, or slightly hardier.

Virus and Virus-Like Diseases Affecting Grapevines in New York Vineyards

Abstract: Three grapevine diseases of economic importance that have been identified in New York State are described here. One disease is induced by tomato and tobacco ringspot viruses and causes a decline of grapevines. A second disease is characterized by trunk cankers that enlarge gradually and kill the grapevines. Eutypa armeniacae Hansf. & Carter is always isolated on artificial media from established cankers and is likely the causal agent involved. The third disease with downward curling and yellowing of leaves, delayed ripening of shoots, and shriveling of berries is of limited occurrence and the causal organism is unknown.

Effect of Maturation on the Lipid Content of Concord Grapes

Abstract: An investigation was conducted to determine the lipid composition and fatty acid distribution of Concord grapes during maturation. Fruit samples were collected at four maturity levels from two Ohio vineyard locations. The crude lipid content of the berries was generally highest at veraison, approximately 0.23%. The neutral lipids tended to increase during maturation, while the polar lipids decreased. At harvest, the crude lipid content of the Concord samples was 0.20%; of this approximately 67% was neutral lipids and 33% polar lipids. The fatty acid distribution of both lipid fractions was predominated by myristic, palmitic, and stearic acids.

Effect of Site on Cold acclimation And Deacclimation of Concord Grapevines

Abstract: The effect of site on cold hardiness of Vitis labruscana Bailey 9Concord9 grapevines was investigated in southwestern Michigan. Air temperatures were consistently lower for a poorly air-drained low site than for a nearby well-air-drained high site. Seasonal hardiness changes followed seasonal changes in air temperature. Canes acclimated faster and to a greater degree of hardiness on low site vines than on high site vines. Both site and compound (primary vs. secondary shoot primordia) bud differences were important in determining bud hardiness. High site buds tended to be less hardy than low site buds. Early spring deacclimation status indicated that bud hardiness differences were due to site-induced differences in air temperature, while inherent differences between the primary and secondary bud were solely responsible for differences in late spring bud hardiness. The two sites generated distinct temperature-induced microclimates where differences in vine adaption were possible. Site induced air temperature and bud differences appeared to interact to influence cold hardiness of Concord grapevines during acclimation and deacclimation. Concord grapevines apparently adapted to lower fall, winter, and spring air temperatures through exposure.

The Effects of Girdling and Ethephon Treatments on Fruit Characteristics of Red Malaga

Abstract: The response of Red Malaga to ethephon, (2-chlorethyl) phosphoric acid, and girdling was determined in 1974 and 1975. Both girdling and ethephon increased color development as indicated by the amount of fruit meeting U.S. No. 1 color standards at first harvest. Girdling increased soluble solids in both years and decreased berry weight in 1974. Ethephon decreased total acid in 1974. Berry firmness was not affected by either girdling or ethephon.

Effect of Temperature and Length of Storage, Root Growth and Termination of Bud Rest in Zinfandel Grapes

Abstract: At storage temperatures of 0°, 3.9°, and 10°C, eight weeks (1,344 h) sufficed to produce maximum budbreak, although termination of rest was generally slower at 10°C. However, at all temperatures studied, three days of storage was sufficient for some budbreak. Resting buds may cause trouble for the grape grower if cuttings are made too early without eight weeks of cold storage. At 37°C, storage longer than three days killed the buds. Growth of shoots usually preceded root growth. Cuttings stored eight weeks at 0°, 3.9°, and 10° produced shoots respectively, 14, 14, and 25 days earlier than root initiation. Curves for root growth generally followed those for shoots. There have been a few studies on the effect of low temperatures on termination of bud rest in grapes (2,3,4,5,6,7,8), but the required minimal amount of cold has not been delineated. Our research had three main objectives: 1) to study the effect of length of storage and temperatures on bud rest and time of rooting of grape cuttings, 2) to determine the temperature requirements needed to terminate rest, and 3) to correlate termination of rest with beginning of root growth.

Salinity Effects on the Ion Composition of Fruiting Cabernet Sauvignon Vines

Abstract: Glasshouse-grown `Cabernet Sauvignon9 vines ( Vitis vinifera L.) were irrigated with nutrient solution containing 1, 10, 25, 50 or 75 mM NaCl. Shoot growth was substantially reduced by the 50 and 75 mM NaCl treatments. A great increase in the chloride content of bleeding sap from decapitated plants occurred above the 25 mM salinity level. The interrelations of sodium, chloride and potassium levels in petioles, laminae (blades) and berries for the various salinity treatments are described. Replacement of potassium by sodium was evident in petioles, but not in laminae or berries. A consequence of increased salinity in the rootzone of vines was a higher level of sodium and chloride within fruit and leaves. These observations are discussed in terms of possible effects on wine composition.

Grapevine Propagation. IX. Effects of Temperature, Refrigeration, and Indole Butyric Acid on Callusing, Bud Push, and Rooting of Dormant Cuttings

Abstract: Freshly made cuttings formed callus first at the base of the cutting in 4-17 days at 29.5°C. The days, as also in the figures given below, depended upon the variety studied. Lower temperatures required more time. The time required for callus formation appeared to be independent of the time of the season. The formation of roots at the base of freshly made cuttings required 10-24 days at 29.5°C. Lower temperatures required a longer period. Root formation was not affected by the time of season the cuttings were made. Bud push required 17-31 days in November, December, and January at 29.5 and 23.5°C. In February only 5-14 days were required at 29.5 and 23.5°C for the buds to push. In March, bud push occurred in 3-9 days at 29.5 and 23.5°C. Cuttings held in refrigeration before growth required a longer time for callusing, for roots to appear, and for the buds to push. Indolebutyric acid reduces the time required for cuttings to callus and roots to appear. Bud push is not affected.

Storage Stability of Juices and Jellies Made from Muscadine Grapes (Vitis Rotundifolia Michx.)

Abstract: Processed juice samples prepared from black-skinned muscadine grapes were unstable during storage at 21°C. Severe fading and browning of juice products occurred within three weeks with browning being the most noticeable change. Color changes during storage of bronze-colored juices and jellies were less noticeable. Color stability was related to initial pigment content and to cultivar. Jellies had more storage stability than juices. Refrigeration was most effective in maintaining color and flavor of juice. Sulfur dioxide improved retention of juice color but ascorbic acid accelerated degradation.

The Nature and Cause of Cap-Liquid Temperature Differences During Wine Fermentation

Abstract: During pilot-scale fermentations of grape musts in 200 and 250-gal tanks the temperatures of bulk liquid and of cap were measured by thermocouples and a recording potentiometer. Periodic samples of the bulk liquid and of liquid expressed from the cap were analyzed for alcohol and reducing sugar. The results show that the large temperature rise in the floating cap during fermentation on the skins is caused by a faster fermentation of the sugar in the liquid adhering to the cap than in the bulk liquid. Temperature differentials between cap and liquid were maximum, about 15 to 20°F (8 to 11°C), during the early stages of vigorous fermentation. Vertical and lateral temperature gradients were significant in both cap and liquid, though greater in the cap. On the other hand, the temperatures during the fermentation of free-run juice were essentially uniform throughout the tank liquid.

Colloidal Silicon Dioxide as a Fining Agent for Wine

Abstract: "Kieselsol," a generic name for an aqueous colloidal suspension of silicon dioxide, was first used in Germany as a fining agent in conjunction with gelatin during World War II, when tannin was unobtainable. It fell into disuse until recently, when a review of its physical and chemical characteristics indicated that it would be a useful and desirable substitute for tannin in wine and fruit-juice fining. Freshly fermented apple wine was employed in a comparison between tannin-gelatin and Kieselsolgelatin finings.

Effect of Grape Cluster Rot on Wine Quality

Abstract: The loss in quality of white wine resulting from the use of grapes at various stages of rot injury was determined. Grapes with 0% produced wine of best quality. Clusters with 5-10% rotten berries resulted in a marked reduction in wine quality, though still acceptable. With 20-40% rot, the decrease in quality was more marked. Wine from clusters with 80% rot was totally rejected. An increase in cluster rot was accompanied by parallel reductions in both yield per unit area and the quantity of juice obtained per unit of grape weight.

Hygiene in Modern Bench-Grafting

Abstract: Long-term investigations and experiments in modern bench-grafting at the Institute for Vine-Breeding and Vine-Grafting of the Hessian Research Institute (Geisenheim, West Germany) are reviewed. Treatment of grafting material with a Chinosol solution (8-hydroxychinol sulfate-potassium sulfate) has proven effective against Botrytis cinerea Pers., Phomopsis viticola Sacc., and other fungus infections and has significantly increased the successful take and rooting of grafts. The factors determining the success of the treatment were shown to be concentration, temperature, and contact period. Found most effective for a prestorage treatment was a concentration of 0.5% and a soaking period of 15 hours at 10-18°C. Grafting material cut to length ahead of time can then be stored in plastic sacks at 1°C in the presence of free water. Chinosol is also effective in treating material freshly cut to proper length as well as one-year-old rooted grafts and cuttings. Hygienic methods of paraffining and callusing are reviewed. Treatment with 0.05% Chinosol solution, as well as a new agent, is recommended. Recent experiments have demonstrated that sterile Perlite is the best material for topping-off the callusing boxes and that it can perhaps eliminate the need for grafting wax. Perlite allows a significant level of light penetration and the young shoots begin their photosynthetic activity earlier.

Relationship of Soluble Solids and Berry Weight to Airstream Grades of Natural Thompson Seedless Raisins

Abstract: In 1973, Thompson Seedless grapes were harvested on 2 dates from 7 vineyards at Davis and in Fresno and Madera Counties. Berries were sampled from each harvested cluster, weighed individually, and then crushed for total soluble solids content (9). The remaining fruit was sun-dried on trays. The raisins were graded with an airstream sorter, and the grades were correlated with fresh-fruit data using stepwise regression and correlation analyses. Mean soluble solids content (°Brix) and fresh berry weight contributed in a significant way to the correlations with raisin grades, but standard deviations did not. When the fresh-fruit data were segregated for a negative or positive relation between soluble solids and berry weight, high correlations were developed between percent B and better raisin grade (Y) and °Brix and berry weight (X). When b was positive R 2 = 0.998 * and Se = 1.8; when b was negative, R 2 = 0987 ** and Se = 2.0.