Calibration models for routine analysis of cider by mid-infrared spectroscopy

Partial least square regression was used to develop different calibration data sets for multi-parameter routine analysis of ciders. Parameters included were those related with the monitoring of fermentation process and cider quality: specific gravity, total and volatile acidities, alcoholic proof, pH and fructose. Calibration performances were evaluated by means of the prediction residual sum of squares (PRESS), the root mean squared prediction error of cross-validation (RMSECV) and the residual predictive deviation (RPD) values (ratio of the standard deviation of the population to the standard error of cross-validation). Validation of the models was assessed in terms of accuracy and precision. Mean recoveries of the predicted results compared to the reference values were close to 100%, with repeatability and reproducibility similar to those of the reference methods.     

Alternative woods for aging distillates-an insight into their phenolic profiles and antioxidant activities

Work has commenced on the study and characterization of wood native species (oak, chestnut, cherry, alder, ash, and beech), employed to a minor extent in enology, for their application in the elaboration of distillates. To this end, furanic and low molecular weight phenol compounds, total phenolic content, and antioxidant activity in alcoholic extracts by maceration of wood chips at 2 toasting levels were studied. Significant differences between samples, technologically relevant, were due both to species and toasting time. Furthermore, extracts showed interesting antioxidant activities equivalent in some cases to than those reported for alcoholic beverages aged in wood.     

Yeast species associated with the spontaneous fermentation of cider

This paper reports the influence of cider-making technology (pneumatic and traditional pressing) on the dynamics of wild yeast populations. Yeast colonies isolated from apple juice before and throughout fermentation at a cider cellar of Asturias (Spain), during two consecutive years were studied. The yeast strains were identified by restriction fragment length polymorphism analysis of the 5.8S rRNA gene and the two flanking internal transcribed sequences (ITS). The musts obtained by pneumatic pressing were dominated by non-Saccharomyces yeasts (Hanseniaspora genus and Metschnikowia pulcherrima) whereas in the apple juices obtained by traditional pressing Saccharomyces together with non-Saccharomyces, were always present. The species Saccharomyces present were S. cerevisiae and S. bayanus. Apparently S. bayanus, was the predominant species at the beginning and the middle fermentation steps of the fermentation process, reaching a percentage of isolation between 33% and 41%, whereas S. cerevisiae took over the process in the final stages of fermentation. During the 2001 harvest, with independence of cider-making technology, the species Hanseniaspora valbyensis was always isolated at the end of fermentations.     

Effect of cider maturation on the chemical and sensory characteristics of fresh cider spirits

The influence of cider maturation on the chemical and sensory characteristics of fresh cider spirits was evaluated in the present study. To this end, a single-factor experiment with three maturation levels and five replicates (ciders) per level was developed. Level 1 corresponded to spirits obtained when alcoholic and malolactic fermentation of the ciders ceased, Level 2 corresponded to spirits obtained from ciders with a volatile acidity of 1.0 g/L acetic acid, while Level 3 corresponded to spirits made from ciders with a volatile acidity of 1.5 g/L acetic acid. Cider maturation significantly influenced the composition of the spirit as regards the ethyl esters of the major organic acids of cider (lactic, acetic and succinic). It also significantly influenced the content of aromas produced by bacterial activity (2-butanol, 2-propen-1-ol, 4-ethylguaiacol and eugenol), the concentration of which was found to increase with higher levels of maturation. The attributes “spicy” and “sweetness” were likewise influenced by the level of cider maturation. The distillates made from the most matured cider (volatile acidity 1.5 g acetic acid/L) scored better for “odour quality”.     

Characterization of Cider Brandy on the Basis of Aging Time

ABSTRACT: To characterize cider brandies on the basis of age, chemometric techniques (principal component analysis, linear discriminant analysis, and Bayesean analysis) together with contents of volatile, furanic, and phenolic compounds were used. Significant principal components computed by a double cross-validation procedure allowed us to visualize the structure of the database as a function of the aging time to which the cider brandies had been subjected. Feasible and robust discriminant rules were computed and validated by a cross-validation procedure that allowed suitable classification of fresh and aged brandies, obtaining classification hits >; 90%. The most discriminant variables for characterizing cider brandies according to their aging level were as follows: ethyl caprylate > ethyl isovalerate > 1-propanol > hexyl acetate.     

Chemical and sensory changes in fresh cider spirits during maturation in inert containers

BACKGROUND: Fresh cider spirits are alcoholic beverages mainly constituted by volatile compounds from apples that are formed during fermentation or generated during distillation. In this study the chemical and sensory changes that take place during the maturation of fresh cider spirits in inert containers made of stainless steel and glass were investigated. RESULTS: The type of container did not influence the maturation process for any of the studied compounds. Esterification, acetalisation and hydrolysis reactions occurred during the maturation of cider distillates over 24 months, giving rise to several changes in the original composition of this alcoholic beverage, but neither oxidation nor evaporation reactions were detected. A decrease in ethyl acetate, ethyl lactate, diethyl succinate and acetal was observed and an increase in fatty acid ethyl esters and 1,1,3‐triethoxypropane. Likewise, the sensory evaluation of the spirits was significantly influenced by the maturation time, with matured samples obtaining higher scores than fresh ones. CONCLUSION: The presence of reactive compounds in recently distilled products makes a period of around 12 months of maturation advisable to reach equilibrium and to improve the sensory assessment of cider distillates consumed in the fresh state. Copyright © 2010 Society of Chemical Industry     

Determination of volatile compounds in apple pomace by stir bar sorptive extraction and gas chromatography-mass spectrometry (SBSE-GC-MS)

A method based on stir bar sorptive extraction combined with gas chromatography-mass spectrometry detection (SBSE-GC-MS) has been optimized with the aim of applying it to the analysis of apple pomace. The method allowed the identification of 124 volatile compounds after 3 h of extraction with a precision (RSDs) ranging between 2% (linalool) and 11% (ethyl hexanoate). Its use in analyzing varietal apple pomace revealed the interest of this substrate as regards its content in aromas. From a semi-quantitative point of view, the higher content in aldehydes and esters of the Blanquina variety is worth highlighting, as are the greater concentration of acids in the Clara variety and the higher content of terpenes and norisoprenoides in the Coloradona variety. In contrast, the Ernestina and Perico varieties presented the lowest levels of aromas. PRACTICAL APPLICATION: The analysis of varietal apple pomaces showed the importance of this type of waste in the food industry, both for its content in aromas such as for its use as substrate in biotechnological processes.     

Determination of ethyl carbamate in cider spirits by HPLC-FLD

An analytical method based on HPLC-FLD with prior derivatization with 9-xanthydrol for the determination of ethyl carbamate (EC) in cider spirits is reported. The parameters usually examined in the method validation were evaluated. Good linearity was obtained with a correlation coefficient exceeding 0.9999, the limits of detection and quantitation being 1.64 and 3.56 μg/L, respectively. Recoveries ranged between 94% and 98%, while the precision of the method was <5% (RSD). The method was used to determine EC in samples from different origins with the aim of completing the characterization of cider spirits. Values obtained were usual for this type of drink, ranging between the lower limit of quantitation and 67 μg/L.     

Production of spirits from dry apple pomace and selected yeasts

Apple pomace spirits were made from dry pomace and selected yeasts strains. Two strains of indigenous cider yeasts (Saccharomyces cerevisiae and Hanseniaspora uvarum) as well as a commercial enzyme combined with a wine dry yeast were tested. The differences between distillates were studied by means of chemical and sensory analysis. According to the results of this study, treatment with enzymes with pectin methylesterase activity led to excessive levels of distilled methanol, and hence it use is not advisable. In contrast, the indigenous yeasts produced lower concentrations of methanol. Moreover, using different yeast species allows the production of spirits with important differences in their aromatic composition, which is certainly interesting from a commercial point of view. Furthermore, the results showed that drying the apple pomace allows it to be preserved in good condition, thus solving the problem of the seasonality of the raw material for making apple pomace distillates.