The blackberry, originated in the tropical zones of the American continent, is highly sought after because of its smell, taste, color, and high nutritional value. It can be used in numerous food products such as juices, ice cream, and marmalades and it has nutraceutic applications [1].

One of the agroindustrial transformation processes for blackberry is to produce wine by subjecting the fruit to a normal alcoholic fermentation process in accordance with [2] the Colombia Technical Standard NTC 708.

Moderate red wine consumption has beneficial effects on health given its content of antioxidants, originating mainly from its phenolic compounds [3].

Blackberry wine contains some of the compounds that are part of this group of bioactive substances, such as bioactive flavonoids, to which anthocyanins belong. The latter are antioxidant compounds can reduce pro-oxidant substances, even in low concentrations and they promote the formation of low toxicity products [4]. Their associated benefits include the protection of the circulatory system and the prevention of neurodegenerative diseases and cancer, among others [5,6].

The color of the wine is also due to its chemical composition, mainly due to the fruit's phenol content, responsible for developing the color during the winemaking process [7,8].

The flavonoid compounds include phenol acids, tannins, anthocyanins, anthocyanins, etc., found in the seeds, in the vacuoles of the plant cells and in the fruit pulp. These contain aromatic rings responsible for the aroma and smell of the wine, which develop during the winemaking process [9].

Anthocyanins and tannins give the wine its characteristic color. Anthocyanins are natural pigments present all over the plant and in the ripe fruit, which can be red, violet and blue [10]. Tannins have a Flavan-3-ols structure, which belongs to the flavonoid family, responsible for the bitter, astringent taste, body and the wine's aging capacity [11].

The correct selection of strains of yeast is fundamental to guaranteeing good fermentation and, therefore, a quality wine [12]. As such, a proposal was made to make blackberry wine, monitoring the physiochemical and microbiological parameters throughout the process involving alcoholic fermentation, clarification, maturation and aging.

The study was carried out in the Cesurcafe Laboratory and the Microbiología de Alimentos Laboratory at the School of Engineering at Universidad Surcolombiana - Neiva.

By using the extractor, it was possible to obtain a wine-colored juice given that the pressure exerted on the fruits allowed the extraction of the juice in the drupes and did not affect the fleshy receptacle, which was white.

A dry red wine was obtained with a pH=3.26; % malic acid = 0.17, °Brix=6.93; % Alcohol=14.4; Tone=0.11; Chroma=11.90; Viscosity=1.46 cP (Table 1 and 2)

Table 1

Source: Adapted from Oviedo M., Lozano J., 2016.

Table 2

Source: Adapted from Oviedo M., Lozano J., 2016.

The most highly assessed characteristic by the tasters was the color, with a score of 9, where it was possible to see that the pigment that give blackberries their color passed to the wine, and improved during clarification and maturation in casks, and were preserved as much as possible during the bottle ageing process. The smell was the second best assessed characteristic with a score of 8. The rest of the characteristics fell within the product acceptability range and did not present statistically significant differences (p>0.05).

For the pairing process, the best products to accompany the wine were cherry and ham.

Tables 1 and 2 present the data obtained for each of the parameters measured.

The blackberry must had a soluble solids content of 7.2, which made it necessary to ameliorate or chaptalize the juice in order to aid the metabolic activity of the S. cerevisiae var. Bayanus strain and, thus, the fermentation process. The pH and acidity as a percentage of malic acid presented statistically significant differences (p<0.05) between days 0 and 135 (Table 1). During fermentation the soluble solids diminished due to the metabolic activity of the different strains of yeast, whose initial population was of 5.55±0.07 Log cfu/mL (Table 1). This grew in the nutritional conditions of the chaptalized blackberry must until reaching a population of 8.04 ±0.07 Log cfu/mL on day 2.

The stationary phase continued to day 4 and from day 5, there was no growth of viable yeasts, which may be attributed to the production of ethanol. It is also worth noting that the soluble solids became established as from day 4. The viscosity of the blackberry wine reduced during fermentation due to alcohol production greater than the values obtained by [16].

In the fermentation process, the coordinate a* is constant on days one and two, and increases on day three, favoring the red tone. On day 8, there is a reduction showing statistically significant differences between the beginning and end of the fermentation phase (Table 2) [17]. During the first five days, the tanks were homogenized allowing us to take advantage of the anthocyanins and other phenolic compounds for their diffusion [7]. In the cask process, a* continues to decrease with significant differences (8-76 days), which is attributed to pigments transferred from the wood to the wine [7]. In the bottling process, it became evident that the amber-colored bottles kept the color stable [17] (Table 2).

The b* coordinate displayed constant behavior during days 1 and 2, subsequently increasing up to day 4, due to the homogenization of the treatments, which lasted until day 5. The phenolic compounds are dissolved during fermentation making this the phase that shows the highest value for chromatic coordinate b* [7]. Following this, there is a decrease with significant differences on days 8 to 76, modifying the tonality of the wine in the yellow chromatic coordinate [18], most likely due to the reduction of the polyphenol content over time.

From the beginning of the maturation in casks process (day 15-76), there is a decline due to oxidation because of cask porosity.

When aging the wine in amber bottles (day 76-135), there is no significant differences in the wine for coordinate b*, stabilizing due to the fact that the presence of the reaction's phenolic compounds is lower and does not alter the color of the wine and its reddish tone given by anthocyanins.

In the fermentation process, for coordinate L*, we can see that on days 1 and 2, it is stable, but presents significant differences by the end of the process. During the fermentation process (days 1-15), its value increases due to the presence and reaction of anthocyanins and polyphenols, which are reduced in concentration over time. It is worth mentioning that the remontage process to maintain the homogeneity of the juice in the fermentation tanks increased the values of luminosity. During the maturation in casks process (days 15-76), luminosity reduced with significant differences as the polyphenols are oxidized due to the redox potential. The porosity of the wood together with the presence of elagitannins in the casks may have contributed to the evolution of the color through co-pigmentation and its antioxidant action [7]. The blackberry wine presented values of 11.91 and 0.11 of chroma and tone respectively. According to [19], chroma values close to or greater than 50 indicate vivid colors which does not correspond to this study. Values for tones of between -10 and 10 correspond to red-purple, which, in this case, applies for blackberry wine. By comparing the ΔE of blackberry wine with grape wine, we can observe differences greater than 2.7 CIELab units. This demonstrates that blackberry wine presents chromatic characteristics that are different to grape wine and that can be perceived by the human eye (Fig. 2) [19].

Figure 2 / Source: Adapted from Oviedo M., Lozano J., 2016.

Aging in amber bottles (days 76-135) demonstrated significant differences given the light (UV rays) present in the laboratory, which modifies the color of the wine. This process was implemented given that, according to [20] it improves the stability of a number of different parameters. As the wine is not in contact with oxygen, the components react due to biochemical processes, in particular the phenolic compounds (tannins), responsible for the wine's longevity. The wine's aroma and bouquet also improve as they depend mainly on the amount of polyphenols, such as esters, developed through the action of the acids on the alcohols. This is a slow and limited reaction in which volatile acids are formed (ethyl tartrate, diethyl succinate), which can be perceived after several years, and reaching their limit by 50 years. According to the results of the sensorial analysis, we can see that the effect of not having placed the must in the casks for maturation straight after the fermentation process (first five days) meant that the yeast in the must, immediately began the degradation process, increasing acidity, which, in turn, affects the wine's astringency, sweetness and body [20].

A dry blackberry wine was obtained with a red tonality, 6.9 °Brix, 14.4 degrees of alcohol, which are the values established in the NTC 708, recommended for pairing with ham and cheese.