A review of potassium nutrition in grapevines with special emphasis on berry accumulation

Potassium (K) is essential for vine growth and yield. Grape berries are a strong sink for K, particularly during ripening. Excess K levels in grape berries may have a negative impact on wine quality, mainly because it decreases free tartaric acid resulting in an increase in the pH of grape juice, must and wine. In Australia, high K status is common in most vineyards, which reflects the high K and high pH values of most Australian grape juice. This necessitates pH adjustment during the vinification process, and tartaric acid addition is a common practice in most Australian wineries. High K concentration may also lead to excessive loss of the additional tartaric acid by precipitation as potassium bitartrate and, as a consequence, pH adjustment becomes more difficult and expensive. Ensuring naturally low K levels in the berry will help reduce costs of input and waste management at the winery. Potential vineyard management options to manipulate berry K accumulation include selective use of rootstock/scion combination, canopy management and irrigation strategies. However, the impact of these practices on determining the optimum K concentration requires careful calibration of production parameters and the desirable grape juice and wine quality in relation to tissue K concentration. This paper reviews and discusses the possible functions of K in grape berries, translocation of K into the berry, and genetic and cultural factors that may affect the accumulation of K in the berry. This will help to identify the key research and management strategies needed for controlling K concentrations in grape berries.     

Limonoid Glucosides in Fruit, Juice and Processing by-products of Satsuma Mandarin (Chus unshiu Marcov.)

In a study on improving utilization of waste from processing of Satsuma mandarin (Citrus unshiu Marcov.) the limonoid glucosides of fruit, juice, and by-products were measured using HPLC and TLC. All materials had the 17-β-D-glucopyranoside derivatives of limonoids reported in other commercial citrus fruit. Citrus molasses was a good source for industrial scale extraction of limonoid glucosides. An extraction system using polystyrene divinylbenzene resins, was developed which could be expanded to industrial scale.     

Exclusion of sunlight from Shiraz grapes alters wine colour, tannin and sensory properties

The aim of this study was to determine how changes in grape composition brought about by artificial shading (sunlight exclusion) influence wine properties including colour, flavonoid composition and sensory attributes. Prior to flowering, bunches of Shiraz grapes were enclosed in boxes designed to eliminate light without altering bunch temperature and humidity. This artificial bunch shading had little effect on berry ripening and accumulation of sugar but at harvest the shaded bunches had smaller berries and higher seed weight, juice pH and titratable acidity. The amount of anthocyanins in the fruit was not changed significantly but anthocyanin composition in the shaded berries was shifted towards dioxygenated anthocyanins (the glucosides of cyanidin and peonidin derivatives). Shaded fruit had increased seed tannins and decreased skin tannins but the largest relative change in flavonoids was a marked decrease in flavonols in the shaded fruit, similar to previous studies. Wines made from shaded fruit had lower wine colour density, total phenolics, anthocyanins and tannins when the wine was bottled and after ageing for up to three years. Analysis of potential flavour compounds following acid hydrolysis indicated that the wines made from shaded fruit had decreased levels of glycosides of β-damascenone and 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN). Sensory analysis of the wines indicated no significant difference in aroma attributes but the wines made from shaded fruit were rated lower for astringency, fruit flavour and flavour persistence in-mouth sensory attributes. The results indicate that extreme shading of Shiraz fruit can decrease wine colour, anthocyanins and tannins as well as altering sensory attributes.     

Effect of Cryoprotectants on Frozen Whitefish Fillets

Whitefish fillets (Coregonus cupleaformis) were treated with sodium tripolyphosphate (STP), monosodium glutamate (MSG) or a high-pH buffer by high pressure injection, then frozen and stored at ?12°C. Control samples included untreated fillets stored at ?12°C and ?60°C, and STP-dipped fillets (?12°C). Samples treated with STP or high-pH buffer showed better textural properties (reduced centrifugal drip, cooked drip and firmness) than untreated control samples. High pressure injection of STP was not significantly better and sometimes less effective than surface application. Sensory analysis at 18 wk revealed that STP-treated samples (?12°C) were significantly preferred over untreated control samples (?12°C) but not over ?60°C control samples.     

ON THE APPARENT FRACTAL DIMENSION OF SOUND BURSTS IN ACOUSTIC SIGNATURES OF TWO CRUNCHY FOODS1

The jaggedness of the filtered and compressed acoustic signatures of cheese balls and croutons at various levels of water activity was determined in terms of an apparent fractal (Kolmogorov) dimension. The plot of the mean dimension vs water activity had a characteristic sigmoid shape that could be adequately described by a modified version of the Fermi equation. Regression analysis yielded that the apparent fractal dimension, D_fK, of the cheese balls and croutons when dry was around 1.45 and 1.38, respectively. The inflection point, a_wc, that is, the water activity level where half the drop in D_fK occurred, was a_wc= 0.50 and a_wc= 0.55, respectively. The steepness of the jaggedness versus water activity relationship in terms of the a_w range where about 90% of the drop of jaggedness occurred was 0.27 in the cheese balls and about 0.29 in the croutons.     

Algorithms for Finding Repeated Game Equilibria

This paper describes computational techniques for finding all equilibria in infinitely repeated games with discounting and perfect monitoring. It illustrates these techniques with a three player Cournot game. This is the first infinitely repeated three player game ever solved. The paper also presents the solution for the set of equilibria in a two country tariff war. In both games the set of equilibria is large even when the players are not patient.     

DEVELOPMENT OF ACIDIFICATION PROCESSING TECHNOLOGY TO IMPROVE COLOR AND REDUCE THERMOPHILIC SPOILAGE OF CANNED MUSHROOMS

An acid vacuum hydration process followed by canning in EDTA/brine was evaluated for improving color and reducing thermophilic spoilage of canned mushrooms. Blanching in citric, fumaric or phosphoric acids and vacuum hydration in 0.05 M citric acid (pH 3.5) improved the color of the canned product significantly over untreated controls. EDTA (500 ppm) in the canning brine further improved color. Application of the citric acid vacuum hydration process to 227 kg quantities of fresh mushroom tissue in a commercial cannery resulted in no loss in canned product yield, significantly improved product color, greatly minimized thermophilic spoilage and did not significantly influence flavor and texture.     

Creep-Sintering and Microstructure Development of Heterogeneous MgO Compacts

Simultaneous creep and densification and the microstructure development of magnesium oxide powder compacts were studied at 125°C and for applied stresses of up to 0.25 MPa. Die-pressing the powder into compacts with a relative green density of ∼0.40 led to an approximately bimodal distribution of pores, with one fraction having sizes of the order of 10 times the (initial) particle size and the other fraction having pore sizes of the order of the particle size. The presence of the large pores in turn gave rise to rather unusual sintering effects. After first decreasing with relative density (ρ), the densification rate (dρ/dt) and the creep rate (dɛ/dt) then increased dramatically for 0.6 < ρ < 0.75. This range of ρ corresponded to the stage of microstructure development when grain growth and coalescence of the smaller pores have created a more uniform pore distribution. Above ρ∼ 0.75, both dρ/dt and dɛ/dt again decreased with ρ. These trends in the densification behavior are discussed in terms of material parameters such as the equilibrium dihedral angle and the pore coordination number.     

Preparation, Characterization, and Melting Point of High-Purity Lithium Oxide

High-purity lithium oxide was synthesized by thermal decomposition of the peroxide at temperatures up to 1070 K under dynamic vacuum. Analyses of typical preparations gave carbonate 0.01 to 0.02%, hydroxide 0.0 to 0.2%, sodium 0.002%, manganese 0.0004%, and lithium oxide 99.8 to 100.0%. The corrected melting point was measured as 1711±5 K based on the thermal arrest observed when molten specimens were cooled.