Effect of HHP and UHPH High-Pressure Techniques on the Extraction and Stability of Grape and Other Fruit Anthocyanins.

The use of high-pressure technologies is a hot topic in food science because of the potential for a gentle process in which spoilage and pathogenic microorganisms can be eliminated; these technologies also have effects on the extraction, preservation, and modification of some constituents. Whole grapes or bunches can be processed by High Hydrostatic Pressure (HHP), which causes poration of the skin cell walls and rapid diffusion of the anthocyanins into the pulp and seeds in a short treatment time (2-10 min), improving maceration. Grape juice with colloidal skin particles of less than 500 µm processed by Ultra-High Pressure Homogenization (UHPH) is nano-fragmented with high anthocyanin release. Anthocyanins can be rapidly extracted from skins using HHP and cell fragments using UHPH, releasing them and facilitating their diffusion into the liquid quickly. HHP and UHPH techniques are gentle and protective of sensitive molecules such as phenols, terpenes, and vitamins. Both techniques are non-thermal technologies with mild temperatures and residence times. Moreover, UHPH produces an intense inactivation of oxidative enzymes (PPOs), thus preserving the antioxidant activity of grape juices. Both technologies can be applied to juices or concentrates; in addition, HHP can be applied to grapes or bunches. This review provides detailed information on the main features of these novel techniques, their current status in anthocyanin extraction, and their effects on stability and process sustainability.

Emerging Non-Thermal Technologies for the Extraction of Grape Anthocyanins.

Anthocyanins are flavonoid pigments broadly distributed in plants with great potential to be used as food colorants due to their range of colors, innocuous nature, and positive impact on human health. However, these molecules are unstable and affected by pH changes, oxidation and high temperatures, making it very important to extract them using gentle non-thermal technologies. The use of emerging non-thermal techniques such as High Hydrostatic Pressure (HHP), Ultra High Pressure Homogenization (UHPH), Pulsed Electric Fields (PEFs), Ultrasound (US), irradiation, and Pulsed Light (PL) is currently increasing for many applications in food technology. This article reviews their application, features, advantages and drawbacks in the extraction of anthocyanins from grapes. It shows how extraction can be significantly increased with many of these techniques, while decreasing extraction times and maintaining antioxidant capacity.

Use of fumaric acid to control pH and inhibit malolactic fermentation in wines.

Fumaric acid is an additive allowed by the Codex Alimentarius and under evaluation by the International Organisation of Vine and Wine (OIV) that can be used for wine acidification but also to inhibit malolactic fermentation (MLF). The use of 300-900 mg/L of fumaric acid can inhibit MLF in red wines decreasing pH by 0.2 units or more depending on the buffer capacity. When MLF was running with populations of either 7 or 8 log CFU/mL strain alpha (Oenococcus oeni) the application of 600 mg/L of fumaric acid stopped the process for more than 50 days and cells were undetected in specific media. In triangular tastings, fumaric acid was not detected at 300-600 mg/L (p < .05). In subsequent preference tests, some tasters perceived more acidity and body. Fumaric acid is a useful technological additive to improve wine microbiological stability and freshness, also allowing reduction of SO2 levels.

Quality and Composition of Airén Wines Fermented by Sequential Inoculation of Lachancea thermotolerans and Saccharomyces cerevisiae.

This study evaluates the influence of Lachancea thermotolerans on low-acidity Airén grape must from the south of Spain. For this purpose, combined fermentations with Lachancea thermotolerans and Saccharomyces cerevisiae were compared to a single fermentation by S. cerevisiae. Results of all developed analyses showed significant differences in several parameters including acidity, population growth kinetics, concentration of amino acids, volatile and non-volatile compounds, and sensorial parameters. The Airén wine quality increased mainly due to the acidification by L. thermotolerans. The acidification process caused a lactic acid increment of 3.18 g/L and a reduction of 0.22 in pH compared to the control fermentation, performed by S. cerevisiae.

Selected Schizosaccharomyces pombe Strains Have Characteristics That Are Beneficial for Winemaking.

At present, wine is generally produced using Saccharomyces yeast followed by Oenococus bacteria to complete malolactic fermentation. This method has some unsolved problems, such as the management of highly acidic musts and the production of potentially toxic products including biogenic amines and ethyl carbamate. Here we explore the potential of the fission yeast Schizosaccharomyces pombe to solve these problems. We characterise an extensive worldwide collection of S. pombe strains according to classic biochemical parameters of oenological interest. We identify three genetically different S. pombe strains that appear suitable for winemaking. These strains compare favourably to standard Saccharomyces cerevisiae winemaking strains, in that they perform effective malic acid deacidification and significantly reduce levels of biogenic amines and ethyl carbamate precursors without the need for any secondary bacterial malolactic fermentation. These findings indicate that the use of certain S. pombe strains could be advantageous for winemaking in regions where malic acid is problematic, and these strains also show superior performance with respect to food safety.

Combine Use of Selected Schizosaccharomyces pombe and Lachancea thermotolerans Yeast Strains as an Alternative to the Traditional Malolactic Fermentation in Red Wine Production.

Most red wines commercialized in the market use the malolactic fermentation process in order to ensure stability from a microbiological point of view. In this second fermentation, malic acid is converted into L-lactic acid under controlled setups. However this process is not free from possible collateral effects that on some occasions produce off-flavors, wine quality loss and human health problems. In warm viticulture regions such as the south of Spain, the risk of suffering a deviation during the malolactic fermentation process increases due to the high must pH. This contributes to produce wines with high volatile acidity and biogenic amine values. This manuscript develops a new red wine making methodology that consists of combining the use of two non-Saccharomyces yeast strains as an alternative to the traditional malolactic fermentation. In this method, malic acid is totally consumed by Schizosaccharomyces pombe, thus achieving the microbiological stabilization objective, while Lachancea thermotolerans produces lactic acid in order not to reduce and even increase the acidity of wines produced from low acidity musts. This technique reduces the risks inherent to the malolactic fermentation process when performed in warm regions.The result is more fruity wines that contain less acetic acid and biogenic amines than the traditional controls that have undergone the classical malolactic fermentation.

Wood impregnation of yeast lees for winemaking.

This study develops a new method to produce more complex wines by means of an indirect diffusion of wood aromas from yeast cell-walls. An exogenous lyophilized biomass was macerated with an ethanol wood extract solution and subsequently dried. Different times were used for the adsorption of polyphenols and volatile compounds to the yeast cell-walls. The analysis of polyphenols and volatile compounds (by HPLC/DAD and GC-MS, respectively) demonstrate that the adsorption/diffusion of these compounds from the wood to the yeast takes place. Red wines were also aged with Saccharomyces cerevisiae lees that had been impregnated with wood aromas and subsequently dried. Four different types of wood were used: chestnut, cherry, acacia and oak. Large differences were observed between the woods studied with regards to their volatile and polyphenolic profiles. Sensory evaluations confirmed large differences even with short-term contact between the wines and the lees, showing that the method could be of interest for red wine making. In addition, the results demonstrate the potential of using woods other than oak in cooperage.