3 Beståndsdelar
Ett äpple innehåller bland annat ca 80 % vatten, TA (varav x malat), socker, polyfenoler, stärkelse, pektin.
Vid pressning resulterar det i en must med ungefär följande innehåll:
Under jäsning förbrukas sockret av jästcellerna och malat kan metaboliseras till laktat, dels av jästsorter som gör detta och dels av laktobaciller. Biprodukter som tillkommer under jäsning är… alkohol, kolsyra, mm.
Syra, socker, fenoler, citrat
Chemical Composition of Apples Cultivated in Norway [1]
Chemical compositional characterization of some apple cultivars [2]
CONSENSUS DOCUMENT ON COMPOSITIONAL CONSIDERATIONS FOR NEW CULTIVARS OF APPLE [3] also has notes on apple storage.
Soluble solids vs insoluble solids
Carbyhydrates are 80% of soluble solids in citrus, equal glucose and fructose => density in aqueous solution ~ sucrose (1 glucose + 1 fructose)
Nitrogen and potassium (in tree?) has a positive effect on sweetness sensation. Magnesium can increase acidity.
Kväve
Norge [1]
Oxygen
“During pressing, the highest and first oxygen dissolution occurred in the must at 6.8 mg/L, on average. The enzymatic browning reaction after 10 min was responsible for an oxygen uptake above 80%. The addition of sulphur dioxide or maceration of crushed apple results in a must with more oxygen content, however the beverage colour is negatively affected.”
“In alcoholic fermentation, oxygen can be a limiting element for yeast growth and can affect aroma production, mainly those aromas synthesized by apiculate yeasts 10-12. Under cider processing conditions, the yeast (Saccharomyces uvarum) needs 2.0–2.5 mg/L of dissolved oxygen 2. At the beginning of alcoholic fermentation, this element is used in different pathways such as classical respiration, sterol biosynthesis, oxygen detoxification and with other oxidases. These compounds play an important role in the permeability of the cell, affecting its viability (reproductive capacity) and vitality (the ability to produce energy)”
“oxygen can positively or negatively influence the composition and quality of the cider”
From: https://onlinelibrary.wiley.com/doi/full/10.1002/jib.113
Constituents overview
In the whole apple, moisture is the main constitunt, followed by carbohydrates. When moisture is removed, carbohydrates are the main constituent. Protein, fat, and “ash” (minerals and the like) are present in similar proportions (Figur 3.1). Uppgifterna i figurerna nedan är i huvudsak hämtade från [3].
Äpplet innehåller således mest fukt och därefter kolhydrater. Vid pressning ansamlas förstås en större andel vätska i musten och kanske hälften av torrsubstansen medföljer:
Innehålet i torrsubstans är främst kolhydrater (sockerarter, pektin, icke-nebrytbara fibrer etc). Musten har en förhållandevis något högre andel kolhydrater (främst sockerarter) än äpplet och pressresterna.
Socker
Av sockerarterna är fruktos den som förekommer mest rikligt, följt av sukros och glukos. Sorbitol (en socker-alkohol) finns i vissa äppelsorter men vanligen i låga nivåer eller inte alls (vanligast är 0-0.3 g/100g). Enstaka äppelsorter och framför allt vildäpplen kan ha något högre nivåer av sorbitol.
3.1 Organiska syror
Icke flyktiga
“Malic acid and citric acid were the two predominant organic acids in Malus species, whereas the concentrations of other acids were very low or undetectable” [4]
“Malic acid, citric acid, and total organic acid contents exhibited normal distributions with a skew to the right. The total organic acid concentration exhibited significant variation, ranging from 1.72 to 44.63 mg/g fresh weight (FW), with an average of 11.06 mg/g FW (Figure 2; Table S1). Notably, there was almost a 26-fold variation in the total organic acid concentration among the accessions examined. Malic acid was detected in all Malus species, ranging from 1.72 to 29.27 mg/g FW, with an average of 8.90 mg/g FW. Citric acid was predominantly detected in several wild apple species, with content ranging from undetectable to 24.24 mg/g FW. The ratios of malic acid to total organic acid and of citric acid to total organic acid were also calculated (Table S1). In cultivated apple fruits, the ratio of malic acid to total organic acid was as high as100%, indicating that malic acid is the predominant organic acid in cultivated apple. Of 58 wild relatives, 31 (53%) revealed a considerable amount of citric acid, with a content of ≥0.43 mg/g FW; the ratio of citric acid to total organic acid ranged from 5.23% to 60.67%, whilst 27 (47%) showed an extremely low to undetectable concentration of citric acid. This indicated that malic acid and citric acid represent the two predominant organic acids in wild apple species.”
“Fruit acidity in cultivated apples is majorly determined by malic acid, which accounts for up to 90% of total organic acids [6]. Citric acid also exists in mature apple fruits; however, it exhibits a very low to undetectable concentration in cultivated apple”