ENZYMATIC ANALYSIS OF CIDER

Image of a glass of cold cider

Cider is a traditional drink produced from apple juice that ferments naturally to produce a drink with a moderate alcohol content (around 4-8 º), a color ranging from pale yellow to amber, slightly bubbly, very refreshing and with a bittersweet flavor already known in the first civilizations. Its production and consumption are widely spread throughout Europe (it represents 50% of global consumption), especially in the United Kingdom, Ireland, France, Portugal and Spain, as well as in the United States, Canada, Australia and New Zealand, but also in Africa or Latin America.

It comes in multiple varieties that range from low-alcohol sweet drinks (2%) to high-alcohol ciders (14%) with added fruit or herbs; with apple juice content ranging from 35% (minimum allowed by legislation in UK) up to 100%, with different requirements depending on the type of cider and local legislation.

All edible varieties of apples are suitable for making cider, although they are classified into four large groups based on their content of malic acid and tannins: sweet apples (malic below 0.45 g/L, and tannins below 0.2 g/L), ‘sharp’ (malic above 0.45 g/L, tannins below 0.2 g/L), bittersweet (low malic, high tannin) and bitter (high malic, high tannins), which combine to produce ciders with different characteristics of sweetness, acidity and astringency. Other characteristics that affect the quality of apple must would be the pH (necessarily acid, around 3.3 – 3.8), polyphenols, assimilable nitrogen and total sugar. The apple is harvested when the original starch has been transformed into sugar; in this case, a Lugol stain will show its presence only in the outermost parts of the apple.

The production process begins with washing, usually by flotation (since it allows to eliminate defective fruits) followed by washing with water under pressure. Immediately afterwards, the apples are crushed until obtaining a dense pulp that is allowed to macerate briefly to extract part of the polyphenols present in the skin and seeds before proceeding to pressing, in which the pulp is squeezed under moderate pressure so as not to break the seeds (which would provide unpleasant tasting tannins) that lasts between 2 and 4 days. Approximately the yield of 1 kg of apples is 1 L of must. Before starting the fermentation process, the must is clarified, which can be physical (by adding bentonite, for example) or enzymatic (by adding pectinases). With the must already clarified, the necessary acidity, nitrogen and sulfite content corrections are made to ensure a correct fermentation that will transform the sugar into ethanol in a first stage that can last up to 5 months with temperatures between 12 and 18 ºC, followed by a malolactic fermentation (which occurs simultaneously) that will reduce the overall acidity while giving it greater biological stability. This fermentation process, unlike the one that occurs in wine, is carried out in containers that allow the foam to escape, which carries the remains of pectin and other light solid matter, giving rise to a characteristic brownish ‘hat’ during the first days of it (tumultuous fermentation); the rest of the fermentation process is done at a low temperature and minimizing contact with oxygen to avoid the proliferation of acetic bacteria and micrococci. Once the fermentation is finished, a racking is carried out to eliminate all the fermentation lees (called lees) and mixing to adjust the flavor to the desired characteristics before bottling.

Throughout the process, there are several important control stages to ensure a quality product without organoleptic alterations. The first control stage is located in the preparation of the must, which must contain a sufficient amount of reducing sugars (around 150 g / L, of which approximately 60% is as fructose, followed by sucrose and glucose), polyphenols that will provide astringency (between 500 and 3000 mg / L), pH (which must be kept between 3.3 and 3.8), total acidity (provided mainly by malic acid) and assimilable nitrogen sufficient for fermentation to develop (around 80 mg / L).

During the fermentation process it is necessary to avoid the proliferation of lactic and acetic bacteria that would produce unwanted flavors (lactic and acetic pitches, bitterness, framboise) as well as a phenomenon called oiliness due to the secretion of polysaccharides that causes the loss of foaminess and an increase in the viscosity that deteriorates the mouthfeel. The usual form of control is the addition of sulphites to the must that act as bacteriostats and the monitoring is done through the specific measurement of D-lactic acid and acetic acid, among others.

At the end of the malolactic fermentation there is a marked decrease in acidity due to the transformation of the malic into lactic acid. Most ciders look for total acidity concentrations around 4.5 – 7.5 g/L (measured in malic acid; it can be calculated from the tartaric acidity multiplying by 0.89; if these levels are not reached, can be corrected by adding malic acid. It must be taken into account that while in wine production malolactic fermentation is subsequent to alcoholic fermentation, which allows adequate control of the bacterial population between both phases, in the production of Both are made simultaneously, which leads to a much higher concentration of lactic and acetic bacteria both in subsequent maturation and in bottling, so an inadequate control of total acidity can be very problematic later on.

Another important control point is the one prior to bottling, which must ensure physical-chemical and microbiological stability. As in the case of wine, color alterations may appear due to the oxidation of polyphenols (oxidation breakdown), the appearance of iron or copper precipitates (iron or copper breakage) or phosphates (phosphatase breakdown) that can be corrected by adding of a suitable complexing agent such as citric acid (no more than 1 g / L) or tartaric (no more than 2 g / L). Taste alterations may also appear if the cider has not been stabilized microbiologically, as a consequence of the metabolism of glycerol towards acrolein, for which it is necessary to adjust the sulfite levels again and even other procedures such as pasteurization.

Sinatech has a wide range of high-performance reagents for quality control throughout the cider production process, based on official methods of analysis. The DYONISOS system is an optimal tool for the control of the production process, capable of guaranteeing the quality and food safety requirements demanded by the existing regulations.

Image of a bottle pouring cider into a glass with an apple next to it

For more than 10 years, Sinatech’s commitment to the winemaker has been working side by side to provide the most appropriate analytical solutions to the control and monitoring of the winemaking process. Automated methods easily adaptable to any work routine, with a personalized advisory team to help you quickly and smoothly implement.

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