Cold Soak Research Articles

Adsorption and deformation characteristics of coal under liquid nitrogen cold soaking

The research on gas adsorption deformation characteristics of coal under liquid nitrogen cold soaking deserves investigation, as most of the investigation efforts in this field are in a preliminary stage. In this article, the experiments of coal adsorption deformation under different times of liquid nitrogen cold soaking (0, 1, 3, 5, 7 and 9) were carried out. The variation of coal gas adsorption capacity and volumetric strain under different times of liquid nitrogen cold soaking were investigated. Based on thermodynamics, the adsorption strain model of coal was developed, and the relationship between coal adsorption capacity and volumetric strain was discussed. The research results show that: (i) the coal adsorption capacity and volumetric strain both gradually decrease with the increase of the number of liquid nitrogen cold soaking; (ii) the saturated gas adsorption capacity and limit volume strain of coal both show a decreasing trend with the increase of liquid nitrogen cold soaking times; (iii) the volumetric strain of coal under the different times of liquid nitrogen cold soaking first accelerates and then slowly rises with the increase of adsorption capacity. After liquid nitrogen cold soaking, the volumetric strain growth rate of coal gradually decreases; (iv) the coal under different cold soaking times reaches the limit volumetric strain at a pressure (P) that is higher than the pressure (p) required to reach the saturation adsorption capacity, and the values of p and P both show a decreasing trend with the increase of liquid nitrogen cold soaking times; (v) the model results have good predictive effect.

Oil palm empty bunches as a growing media for white oyster mushroom (Pleurotus ostreatus)

The media used to grow oyster mushrooms is sawdust waste, such as sengon, gmelina, and candlenut. Therefore, several researchers conducted research to find alternative media to replace sawdust, such as mulberry pulp, sago pulp, coconut fibre, and bamboo pulp. This research utilizes waste of oil palm empty bunches as a medium used to grow oyster mushrooms. In addition, this study aims to determine the duration of immersion of oil palm empty bunches as a pre-treatment before being used as a growing medium for white oyster mushroom (Pleurotus ostreatus). Before being used as a medium, empty fruit bunches of oil palm are cut into small pieces and then made into powder. The stages in this research are mixing raw materials, composting, making baglog, sterilization, inoculation, incubation, maintenance, and harvesting. There were seven treatments applied in this study, namely immersion in cold water for five days (P1), for seven days (P2), and nine days (P3); immersion in 100 °C hot water for 1 hour (P4), for 2 hours (P5), and 3 hours (P6); without immersion or control (P7). The results obtained are empty oil palm fruit bunches with cold soaking for five days (P1) and hot soaking at 100 °C for two hours can be used as a medium for oyster mushroom cultivation.

Study on the Influence of Liquid Nitrogen Cold Soaking on the Temperature Variations and Seepage Characteristics of Coal Samples with Different Moisture Contents

Due to its advantages such as environmental friendliness and remarkable permeability enhancement effect, the technology of liquid nitrogen cold soaking (LNCS) cracking coal has become a hot spot in the research on coal seam permeability enhancement in recent years. The frost heave force generated by water-ice phase transformation and the temperature stress are the main mechanisms of LNCS cracking water-containing coal. This paper focuses on the effect of LNCS on the temperature variations and seepage characteristics of coal. To further this purpose, the temperature measurement test and the permeability test were conducted on coal samples with different moisture contents under LNCS, respectively. In addition, by comparing the computer tomography test results of coal samples before and after LNCS, the internal pore structure changes of coal samples were further analyzed from a three-dimensional perspective. The test results show that the coal sample with a higher moisture content consumes a shorter time to reach internal temperature equilibrium and experiences faster temperature changes. LNCS can enhance coal permeability, and the growth rate of permeability increases exponentially with the increase of moisture content. After the LNCS treatment, the dried coal sample is mainly sprouting new pores on the basis of primary pores; in contrast, for water-containing coal samples, new pores are sprouted while primary pores will penetrate each other spatially to form a fracture network. In the process of LNCS, moisture has a significant effect on the seepage characteristics of coal, so appropriately increasing the moisture content of the coal seam conduces to achieving a better permeability enhancement effect.

The Natural Durability and Drying Properties of Ganitri Wood (Elaeocarpus sphaericus Schum)

Ganitri (Elaeocarpus sphaericus Schum.) is a fast-growing species that was majority planted in community-based forets in Java. This research aimed to evaluate the natural durability and drying properties of ganitri wood, hence the best uses of the wood can be achieved. The wood durability was tested in laboratory and field scales based on SNI 7207:2014 and ASTM D 1758-02 standards respectively, while the wood treatibilty evaluation used soaking method with 5% borax preservative. The wood drying property was assessed through oven drying at 100°C temperature based on Terazawa method. The resistance of the wood against subterranean termites Coptotermes curvignathus is classified as durability class IV. Ganitri wood was very easy to be preserved with the cold soaking method. Boron retention in ganitri was 22.87 kg.m-³, while its penetration was 27.80 mm or 94.24%. Ganitri had rather poor drying properties, which was prone to surface check. The proper drying for ganitri wood was suggested using initial and final temperatures 53°C and 83°C, respectively, while the initial and final relative humidity were 85% and 30%.

Effects of maceration length after prefermentative cold soak: Detailed chromatic, phenolic and sensory composition of cabernet sauvignon, malbec and merlot wines

Cabernet Sauvignon, Malbec and Merlot grapes were processed with prefermentative cold soak (CS) for 5 days followed by a short maceration time of 5 days (CS + 5d), or a long maceration time of 10 days (CS + 10d). CS did not affect the basic chemistry of the wines, nor improved anthocyanins, polymeric pigments and total phenolics relative to Control wines (10 days maceration). Wine tannins were lowered in CS + 5d wines by 71 % (Cabernet Sauvignon) and by 29 % (Merlot). CIELab coordinates showed a negative impact on L*, C*, and copigmentation in CS wines indicating that these wines were lighter in color than their Control counterparts and these differences could be distinguished by the human eye. Astringency and bitterness were lower in CS + 5d wines, whereas CS + 10d wines showed enhanced fresh fruit aroma, body, bitterness, and astringency.

Integrating bioinformatics with pharmacological evaluation for illustrating the action mechanism of herbal formula Jiao'e mixture in suppressing lung carcinoma

Ethnopharmacological relevanceLung carcinoma (LC) is not only a kind of disease that seriously threatens human life but also an intractable problem in modern medicine. Jiao'e Mixture (JEM) is an innovative Chinese medicine formula with Chinese patent, which is composed of two herbal extracts with a specific ratio–zedoary turmeric oil and medicinal Zanthoxylum bungeanum Maxim(Z. bungeanum Maxim) seeds oil (ZMSO). Zedoary turmeric oil is extracted from dried rhizomes of Curcuma wenyujin Y.H.Chen et C. Ling, which has been reported have an anti-cancer effects. Medicinal ZMSO is a by-product of Z. bungeanum Maxim, refined from kernel shell separation, modern cold soaking and refining technology; JEM is used to treat Lung carcinoma (LC) patients in folk for many years. However, its therapeutic mechanisms for treating LC have not been fully explored. Aim of the studyThe purpose of this study was to explore the therapeutic mechanisms of JEM for treating LC. Materials and methodsThe action mechanism of JEM in LC treatment was analysed by comprehensive network pharmacology approach combined with experimental validation (in vivo and in vitro). ResultsSeventeen active compounds and 457 related targets were collected from the HERB, TCMSP, and Swiss Target Prediction platforms. Nine hundred and thirty-eight LC related targets were obtained from Gene Cards and OMIM databases. Finally, 140 overlapping targets were obtained, which representing the target of JEM in LC treatment. The pathway analysis showed that PI3K-AKT could be a potential pathway for JEM in LC treatment. In vivo results presented that JEM had a good effect in inhibiting the growth of LC tumour cells with high efficacy and low toxicity. In vitro experiments validated that JEM had inhibited LC cells’ proliferation, migration and invasion, and had induced cell apoptosis mainly via PI3K/Akt signalling pathways. ConclusionThe anti-LC activity of JEM might via regulating the PI3K-AKT signalling pathways.This study may provide further evidence for the potential use of JEM in LC treatment.

Study on Temperature Variation and Pore Structure Evolution within Coal under the Effect of Lilquid Nitrogen Mass Transfer.

Liquid nitrogen freezing, which is an effective permeability enhancement technology, has been applied to the extraction of oil, shale gas, and coalbed methane (CBM). This study is aimed at revealing the effect of liquid nitrogen mass transfer on the temperature variation and pore structure evolution within coal. To achieve this aim, first, temperature measurement tests under the action of liquid nitrogen freezing were conducted on saturated and dried coal samples, respectively. Next, the coal samples were subjected to nuclear magnetic resonance and computer tomography tests before and after liquid nitrogen cold soaking to further explore the mechanism of coal temperature variation from a microscopic perspective. The results show that the action of liquid nitrogen mass transfer can accelerate coal temperature variation through coal pore structure and pore water phase change. The thermal stress and frost heave force generated by liquid nitrogen cold soaking exceed the tensile strength of the coal sample, which directly causes crack initiation, expansion, and connection. The mass transfer of liquid nitrogen has a significant promoting effect on pore development. This study provides the technical support necessary for the efficient exploitation of CBM resources and the improvement of CBM extraction rate.

KARAKTERISTIK PAPAN PARTIKEL DARI CAMPURAN LIMBAH AKASIA (Acacia mangium Willd.) DAN KULIT KELAPA MUDA (Cocos nucifera L.)

The aim of this research is to make an effort to utilize forestry waste, in the form of harvesting waste of acacia (Acacia mangiumWilld.) and coconut shells (Cocos nucifera L.) into particle boards by considering the evaluation of the value of particle board characteristics, both physical and mechanical characteristics in accordance with standards JIS A 5908-2003.This study used a factorial analysis where the first factor was the composition of the raw material for acacia: coconut (100: 0, 60:40, 50:50, 40:60 and 0:100). While the second factor is the provision of pretreatment on particles (cold soak, hot soak and without immersion).This analysis was carried out in a completely randomized design (CRD) with three repetitions.The results showed that the composition of the raw materials had a significant effect on the value of water content, water absorption, modulus of rupture and modulus of elasticity.The pretreatment had a significant effect on the thickness swelling, water absorption, modulus of rupture and modulus of elasticity. Meanwhile, the interaction of these two factors has a significant effect on the internal bond value, modulus of rupture and modulus of elasticity.Based on the results, it is known that only the density parameters that meet the JIS A 5908-2003 standard, the moisture content and thickness development parameters have not met the standards, while the mechanical characteristics of the particle board have not met the standards.Overall particle board with the composition of acacia raw material: young coconut 60:40 and heat soaking pre-treatment can produce good quality particle board.

Effect of novel sequential soaking treatments on Maillard reaction products in potato and alternative vegetable crisps

Frying leads to the formation of numerous food contaminants through the Maillard reaction (MR). In this paper, commercially available vegetable crisps were analysed for and established to have high levels of acrylamide. Consequentially, the capability of two novel sequential pre-frying treatments were applied to potato, beetroot and parsnip snacks to inhibit the formation of acrylamide, 5-hydroxymethylfurfural (HMF), glyoxal (GO) and methylglyoxal (MGO) was investigated. Data revealed that immersion in cold tap water for 2 min followed by blanching at 70 ± 2 °C for 2 min (Cold soak, hot soak, (CSHS)) as well as soaking in a 0.01M CaCl2 solution for 2 min followed by blanching at 70 ± 2 °C in 0.1M citric acid for 2 min were both effective pre-treatments for potato crisps, simultaneously decreasing acrylamide concentration under the benchmark level of 750 μg/kg and lowering GO content by 55.19 and 54.67% and MGO concentration by 39.17% and 81.62%, respectively. CSHS was the only efficient treatment for concurrent mitigation of acrylamide (-41.64%) and HMF (-88.43%) with little GO and MGO development in beetroot. Sequential cold soak in 0.01M calcium chloride and hot soak in a 0.1M citric acid solution has been effective in decreasing acrylamide in alternative crisps. However, this led to an increase in HMF, 30 and 20-fold respectively from the initial concentration. Data reveal that the tested mitigation strategies are vegetable specific.

Distribusi, Retensi, dan Penetrasi Bahan Pengawet Ekstrak Daun Tuba (Derris elliptica Benth) pada Kayu Kemiri dan Kayu Agathis (Distribution, Retention, and Penetration of Tuba Leaves Extract (Derris elliptica Benth) on Aleurites moluccana and Agathis Wood)

Wood preservation is carried out to increase the service life of wood with low natural durability. Factors such as wood structure, preservatives, and methods of preservation influence the preservation processes. The aim of this study was to evaluate retention, penetration, and distribution of tuba (Derris elliptica) leaves extract into the candlenut wood (Aleurites molluccana) and agathis (Agathis sp.) wood structures. The wood samples were treated with hot and cold soaking. The duration of hot soaking were 3, 5, and 7 hours, while for cold soaking were 3, 5, and 7 days. The result showed that the highest retention of extract was achieved by cold soaking for 7 days at 9.4 kg m-3, and the lowest retention was achieved by hot soaking for 3 hours at 1.9 kg m‑3. The highest penetration occured by cold soaking for 7 days at 8.08 mm and the lowest was that with hot soaking for 3 hours at 2.81 mm. However, the distribution of the extract in the agathis wood structures could not be detected by stereo microscope. In the the case of the candlenut wood, the extract was distributed in the parenchyma cell.

Application of New Supercritical Extraction Technology in Extraction and Separation of Effective Components of Traditional Chinese Medicine

Supercritical CO2 extraction technology uses supercritical CO2 fluid as extractant to extract and separate effective components from plants from liquid or solid. At present, CO2 is widely used in supercritical fluid, with a critical temperature of 31.265 °C and a critical pressure of 7.18 MPa. The critical conditions are easy to reach. In supercritical state, the density of CO2 fluid is very sensitive to the changes of temperature and pressure, The widely used separation technologies can be divided into two types: membrane separation and traditional separation. The traditional separation methods can be divided into steam distillation, sublimation, cold soaking, precipitation, percolation, decocting method and Soxhlet extraction, etc. These separation methods have certain limitations. In this paper, SFE technology is combined with modern analytical techniques, such as gas chromatography, high performance liquid chromatography, thin layer chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, etc., so that the component analysis can be carried out more efficiently and quickly. Because of the above advantages, SFE is especially beneficial to the extraction of effective components in traditional Chinese medicine and its preparations.

Numerical simulation of the coal temperature field evolution under the liquid nitrogen cold soaking

Liquid nitrogen fracturing technology is largely based on the characteristics of coal and rock destruction caused by its low temperature to achieve the purpose of increasing permeability. The temperature field study is very important in liquid nitrogen cold soaking. In order to study the spatiotemporal characteristics of the internal temperature field inside coal under the liquid nitrogen cold soaking, the overall heat transfer law of coal is discussed. Based on the theory of heat transfer, this paper discusses the heat transfer equation of coal under the liquid nitrogen cold soaking. A cold shock simulation experiment is performed on the coal specimens during the liquid nitrogen cold soaking by the COMSOL software, and the temperature field change of the coal specimens during the liquid nitrogen cold soaking are obtained. In addition, the simulation results are compared with the experimental results of coal specimens under the liquid nitrogen cold soaking to verify the rationality of the theory and simulation analysis. The results show that the temperature field of coal specimens propagates in the form of waves under the liquid nitrogen cold soaking, which gradually decrease with increasing distance. The closer the dried coal specimens are to the liquid nitrogen boundary surface, the greater the temperature impact speed and the shorter the time required to reach a steady state. Both the surface of the coal specimen and its internal temperature change curve can be divided into three typical phases: the accelerated cooling phase, the decelerated cooling phase, and the low-temperature maintenance phase. The laboratory test results have a good correspondence with the numerical simulation results, which show that it is feasible to use numerical simulation to study the temperature field change law of coal and rock under liquid nitrogen cold soaking.

Various adsorbents to improve the filterability of biodiesel

Cold flow properties are the primary drawback to the common usage of biodiesel as an alternative fuel to diesel. Biodiesel's cold flow behaviour is discovered for the main reasons of presence of precipitant or crystal initiate by minor components such as monoglycerides and steryl glycosides. The ASTM test for this precipitant is ‘The Standard Test Method for Determination of Fuel Filter Blocking Potential of Biodiesel (B100) Blend Stock by Cold Soak Filtration Test (CSFT)’. Therefore, in this study, the performance of commercial activated carbon, silica and beach sand as adsorbent is studied in improving the filterability of two different level of refined biodiesel. The adsorbents were used to treat the biodiesel by removing the impurities present in the biodiesel such as the monoglycerides and steryl glycosides compound from biodiesel using adsorption technique. The efficiency of the adsorbent is determined by performing the cold soak filtration test. Based on the cold soak filtration test, precipitate is not visible and the CSTF is within the 360 s limit for the both refined level of biodiesel. However, treatment of these biodiesel with commercial activated carbon, silica and beach sand resulted in further reduce in CSFT. Commercial activated carbon found to be the most effective adsorbent, followed by silica. This is because both adsorbents possessed high surface area of 657.0420 m2/g and 320.2724 m2/g respectively and high pore volume of 0.379097 cm3/g and 0.952320 cm3/g respectively which further enhance its potential as an excellent adsorbent to improve the filterability of biodiesel compared to beach sand which possessed lowest surface area and lowest pore volume of only 1.2630 m2/g and 0.001751 cm3/g respectively.

Reconsideration of regulated contamination limits to improve filterability of biodiesel and blends with diesel fuels

Abstract For the fulfillment of the Directive EU/2001/2018 targets for 2030, one of the main restrictions in the development of biodiesel fuels from sustainable feedstocks are currently the filterability problems. Contaminants such as saturated monoglycerides, sodium soaps and free steryl glucosides in biodiesel fuels have been found to clog fuel filters in vehicles, fuel dispensers and other industrial equipment which reduces the lifetime of the filters, and may result in fuel starvation, with engine operating difficulties and possible fuel-injection equipment damage. From a distilled biodiesel fuel spiked with these contaminants and subsequently blended with diesel fuel, samples fulfilling quality standards were prepared. filter blocking tendency, cold soak filtration test and total contamination tests were measured. It was found that filterability properties were affected always by the highest contaminant contents, both individually and synergistically. Total contamination test presented inconclusive results. The following conclusions were achieved: i) improvements in the precision of filterability and total contamination methods should be searched; ii) future regulations of biodiesel fuels should limit the free steryl-glucoside, saturated monoglyceride and sodium soap contents; iii) the current biodiesel fuel standards around the world do not secure the filterability properties, which could cause premature fuel filter clogging.

Transesterification of Refined Bleached Deodorized Palm Oil (RBD PO) Using Homogeneous Base Catalyst and Methanol and Investigation of Factors Filter Blocking Issue in Palm Based Biodiesel

The aim of this study is to investigate the major properties of biodiesel causing filter-blocking issue in biodiesel especially for palm oil based, to identify the suitable solution to reduce or eliminate these factors for improving the filter properties of the palm based biodiesel by control the specific parameter (mono-glycerides during intermediate process and minimize or eliminate the Steryl Glycoside after post treatment. This study may give significant impact especially to local industry of biodiesel producer which operated with normal transesterification process and using palm base feedstock to conform international biodiesel specification such as ASTM D D7501 (Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels). In this paper the Filter Blocking Tendency (FBT) testing and Cold Soak Filterability Test (CSFT) testing procedure and result will be presented.

Influence of Select Non-Saccharomyces Yeast on Hanseniaspora uvarum Growth during Prefermentation Cold Maceration

This study investigated the effect of select non-Saccharomyces yeast strains on Hanseniaspora uvarum growth and acetic acid and ethyl acetate production during prefermentation cold soak. We tested commercially available non-Saccharomyces yeasts for their ability to reduce H. uvarum growth and acetic acid production during a simulated cold soak in a grape juice-based medium. All tested non-Saccharomyces yeast reduced H. uvarum growth and acetic acid production, with some yeast having a greater impact than others. Following the screening of non-Saccharomyces yeast, we tested 14 different H. uvarum isolates against a selected non-Saccharomyces yeast, Metschnikowia fructicola, and found that all H. uvarum isolates had reduced growth and acetic acid production when grown in co-culture with M. fructicola, with variation between isolates noted. Finally, we evaluated the effect of M. fructicola on H. uvarum during prefermentation cold soak of Pinot noir grapes. Pinot noir grapes were inoculated with a combination of H. uvarum and M. fructicola and cold soaked for six days at 8°C. At the end of cold soaking, treatments inoculated with M. fructicola contained lower populations of H. uvarum and significantly lower acetic acid and ethyl acetate concentrations compared with treatments not inoculated with M. fructicola. After the completion of alcoholic fermentation, wines where M. fructicola was added contained significantly lower ethyl acetate but no differences in acetic acid concentration. These results suggest that adding select non-Saccharomyces yeast may be another method to reduce the risk of spoilage by H. uvarum during prefermentation cold soaking.

A novel quality evaluation method for magnolia bark using electronic nose and colorimeter data with multiple statistical algorithms

Magnolia bark ( Magnolia Officinalis REHD. & WILS. and Magnolia officinalis REHD. & WILS. VAR. biloba REHD. & WILS, Hou Po in Chinese), is widely applied in clinical prescriptions and Chinese patent medicines. Origin place is a crucial factor affecting the quality of Hou Po, and chemical composition is an important index for evaluating its quality, which is closely related to its clinical efficacy. This study aims to develop a novel method for rapidly, accurately and comprehensively identifying the origin places of Hou Po and predicting the contents of its important chemical components. High performance liquid chromatography was used to analyze the contents of magnolol and honokiol and ultra-performance liquid chromatography the contents of magnocurarine and magnoflorine. The cold soak method was used to determine the contents of water-soluble extracts. The E-nose and colorimeter were used to determine the odor and color characteristics, respectively, of the collected Hou Po samples. Using several statistical algorithms, different discriminant models based on the E-nose and colorimeter data were established to distinguish the origin place of Hou-Po and predict the chemical components of honokiol, magnolol, magnocurarine, magnoflorine and water-soluble extracts. The results showed that the Random Forest classifier combined with the ten-fold cross-validation method provided the highest classification accuracy for origin place, accounting for 99.53% among these models. The correlation coefficients between predicted and experimental values of the five chemical components were all higher than 0.96. This study has indicated that the electronic nose and colorimeter are promising methods for evaluating the quality of Chinese herbal medicines both qualitatively and quantitatively.

Preservation of Durian Timber by Kecubung Fruit Extract against Termite Attack

Durian wood is a type of wood that grows in abundance the region of Gunungpati Semarang, Indonesia. Unfortunately Durian timber is included in the type of wood that is not resistant to termite attack, so they need to be preserved in order to increase the durability. One of the plants that can produce natural preservatives is the Kecubung fruits (Datura Metellinn) containing very strong toxins (alkaloids). This research used experimental method, by cold soaking method preservation with concentration of preservative extract of Kecubung fruits 0%, 15%, 20%, and 25%, duration time 120 hours. The result of the experimental research showed that the termite endurance test on durian timber at 0% concentration of preservative (control test specimens) the weight had decreased by 17.89%, while the concentration of preservation at 15%, 20%, and 25% had deceased the weight by 10.49%, 8.78%, and 3.63% respectively. Therefore, preservation of durian timber using cold soaking method at 120 hours by using the Kecubung fruits extract with 25% concentration gives the best result and the Kecubung fruits can be the alternative solution for the wood preservation which is the form of organic compound and environmental friendly.

The Evolution of Thermal Conductivity and Pore Structure for Coal under Liquid Nitrogen Soaking

An experimental system for liquid nitrogen soaking and real‐time temperature measurement was designed and implemented to investigate the characteristics of temperature field changes in coal under liquid nitrogen soaking. Then, the heat conduction law of the coal in the process of liquid nitrogen soaking and room temperature recovery for dry and water‐saturated coal were examined. The microstructure characteristics of the coal before and after liquid nitrogen soaking were analyzed with nuclear magnetic resonance (NMR) technology. The results showed that, during the liquid nitrogen cold soaking process, the heat transfer law of the dry and water‐saturated coal samples exhibited a notable three‐stage distribution. For the room temperature recovery process, the dry and water‐saturated coal samples exhibited rapid heating characteristics, and the cooling rate gradually decreased to zero. NMR test results indicated that the liquid nitrogen soaking increased the number of micro and small pores in the coal. Thermal stress analysis revealed that the thermal stress generated by the dry coal was larger than that produced by the saturated coal, and the damage was primarily caused by thermal stress. However, the permeability of the saturated coal was better than that of the dry coal. The damage on the saturated coal was caused by the volume expansion of pores and fissures caused by water‐ice phase transition.

Heat-Dependent Desorption of Proanthocyanidins from Grape-Derived Cell Wall Material under Variable Ethanol Concentrations in Model Wine Systems.

Desorption of proanthocyanidins (PA) from grape cell wall material (CWM) was investigated in solutions of varying ethanol concentrations and increasing temperature. The results reveal the reversibility of PA-CWM interactions and the role that temperature and ethanol concentration play in the extent of PA desorption. Sequentially raising temperature from 15 to 35 °C resulted in desorption of up to 48% of the initial adsorbed PA. A comparison to a phenolic extraction model showed significant differences between the predicted and actual amount of PA that desorbed from the CWM. This suggests that the initial conditions of temperature and ethanol concentration must be considered when estimating PA extraction in red wine production. Under typical winemaking conditions, a significant amount of PA may be irreversibly adsorbed if exposed to CWM at low temperature (i.e., cold soak). A compositional analysis suggests the selective desorption of large molecular weight PA from CWM under all experimental conditions. Additionally, a preferential desorption of skin-derived PA over seed-derived PA was noted in the absence of ethanol.