Powdered papaya-latex
The drying rate of papaya latex using an oven at 55
oC for 5 hours in Fig 1 showed that varied between 17.39% and 33.33%, with an average of 24.89%. Papaya-latex contains the papain enzyme
(Ningrum et al., 2018). The advantage of using papain enzyme for milk coagulation is its optimal activity at 75
oC, with activity maintained across a broad temperature range of 70-90
oC. The papain enzyme breaks peptide bonds at asparagine-glutamine, glutamate-alanine, leucine-valine and phenylalanine-tyrosine residues.
pH and Lactic-acid
The average pH of Dangke-Cheese at different heating milk and papain concentrations shows in Table 1. When the pH reaches 5.6, curd formation begins. A gel forms at the bottom with a soft texture and white color
(Tarapata et al., 2021). The curd formation process occurs at pH 4.6 (isoelectric point) and casein becomes hollow, slightly stiff and white, with a sour taste and aroma, while the whey is greenish-yellow
(Tserovska et al., 2002). Papain coagulates casein micelles by cleaving the peptide bond between phenylalanine and methionine in k-casein, leading to the formation of para-k-casein and exposing hydrophobic residues. When the pH approaches the isoelectric-point, the casein-micelles attract each other due to the different ionic properties of each molecule, resulting in clumping
(Asaduzzaman et al., 2021).
Variance analysis showed that the heating milk temperature treatment had a very significant effect (P<0.01) on the Dangke-Cheese pH. The Dangke-Cheese pH at 75
oC heating milk ranges from 5.91-6.12; at 80
oC is 6.08-6.27. The lactic-acid produced will lower the pH value (
Hetényi et al., 2011). The results of the least significant difference test (LSD) showed a high difference between 75
oC and other heating milk temperatures, except for 80!. Papain concentrations of 0.3% and 0.5% were significant differences in the pH of Dangke-Cheese, indicating the breakdown of the three-dimensional network in the curd structure, which could release lactose in the curd. Lactic acid bacteria have the ability to convert lactose into lactic acid. Additionally, lactic acid plays a role in the creation of tiny peptides and amino acids through the action of their proteolytic enzymes during the process of cheese manufacture (
Nurye and Wolkero, 2022). The pH of curd ranges from 4.24 to 4.63
(Usmiati et al., 2011). Variance analysis indicated that heating milk significantly affected Dangke-Cheese lactic acid (P<0.01). The average percentage of Dangke-Cheese lactic-acid at 75
oC is in the range of 0.60-0.77%; at 80
oC is 0.34-0.62%; at 85
oC is 0.32-0.73% and it continues to decrease as the Heating-milk-temperature increases.
The LSD test resulted in a high difference between 75
oC and other Heating-milk-temperatures except for 0.4% papain concentration, but there was no difference between 80 and 85
oC, 85 and 90
oC. The concentration of papaya-latex in Dangke-Cheese-making does not affect lactic-acid at 75
oC. The percentage of lactic-acid is inversely proportional to pH. On average, fresh milk contains lactic acid between 0.14 and 0.19%. When milk is stored at room temperature, lactic-acid increases to 0.25%. If acidity continues to increase, casein precipitation occurs when the acidity reaches 0.5-0.65%, or pH reaches 4.64-4.78.
Protein
The protein content determines a food product’s quality. Table 1 shows the results of testing Dangke-Cheese-Protein levels at different heating-milk temperatures and concentrations of wet-papaya-sap. Variance analysis results that different heating-milk-temperatures and papain concentrations significantly affected Dangke-Cheese-protein (P<0.01). The average Dangke-cheese-protein at 75
oC is between 16.13-17.67; at 80
oC is 15.88-17.49%; at 85
oC is 15.82-17.32; at 90
oC 14.25-15.89; at 95
oC is13.98-15.38 and 100
oC is 11.94-14.12%. The insoluble protein in milk, casein-protein, will quickly degrade when heated above 75
oC
(Qian et al., 2017).
Proteins consist of polypeptide chains of amino acid residues through peptide bonds and forming disulfide bonds. The acidic carboxyl group and the weakly basic amino group both combine
via a hydrocarbon chain that is unique to each amino acid. Casein is round and consists of smaller units known as submicelles. Casein is a globular protein with primary, secondary, tertiary and quarter bonds. This bond can break at certain heating levels and will be damaged and broken due to heating above 75
oC.
Protein is the primary nutrient in milk and contains various essential-amino-acids. The protein in milk consists of a water-insoluble-protein, namely casein. Other protein is water-soluble protein, namely a-lactalbumin and β-lactoglobulin. The k-casein molecule contains 169 amino acids. The isoelectric point for the binding of amino-acids 105 (phenylalanine) and 106 (methionine) is easily broken by proteolytic enzymes (renin, papain, bromelain). Starting from amino-acids 106-169, dissolved amino-acids are hydrophilic polar, which are also dissolved in the whey when making cheese. Curd formation increases if the enzyme that separates polar and non-polar amino-acids works optimally.
Fat and carbohydrate
The highest Dangke-Cheese fat content is at 75
oC heating-milk, with a papaya-latex level of 0.3%, around 17.31%. Table 1 shows that fat decreases with increasing temperature. Table 2 explains the effect of 3 heating milk temperatures on carbohydrate, ash and water content using papain with different concentrations. The carbohydrate content, which represents lactose, means there is a fundamental difference between each heating milk temperature, with a range of 2.81-7.32%.
In cheese-making, lactose is generally included in the whey when the curd and whey are separated. The lactose content in cow’s milk is 4.6%, so when using 0.3% papain, the lactose content is only 2.8 at 70
oC, 3.41% at 75
oC and 3.49% at 80
oC heating-milk-temperature. However, what is surprising is that lactose-levels increased sharply when 0.4% and 0.5% papain were added to all heated milk. This may be due to lactose joining the curd during curd formation with increased enzyme activity at papain concentrations above 0.3%.
Minerals
Table 2 shows that changes in mineral content significantly differ between heating milk 70, 75
oC and 80
oC but not between heating milk 75 and 80
oC. This indicates that increasing milk heating will increasingly precipitate and release minerals from protein. Calcium-caseinate-phosphate -micelle is a protein molecule bonded with calcium and phosphate and determines the process of forming curd using acid or enzyme.
In the coagulation process using papain, the casein binds with other casein, releasing calcium from the casein-micelles, increasing the mineral reading and heating-milk-temperature. At least 21 types of minerals are found in milk. The most important mineral is calcium, whose composition is balanced with phosphorus. Calcium in milk is mainly found as calcium-phosphate, calcium-carbonate and calcium-chloride, so it is easily absorbed in the intestine.
Water content
The water content in Dangke-cheese in Table 2 ranges from 60.28 to 70.34%. This water content is still relatively high, so it is still classified as soft cheese, although it is still lower than cottage cheese’s, around 78.3%. The water content is higher at a papaya latex concentration of 0.3% because the 0.3% concentration has not caused all the casein to coagulate and much water is still stored in the curd. This condition causes curd to store water in a three-dimensional-network, fat-protein-water. Data is essential for understanding how heating temperatures and papaya sap concentration impact dangke cheese’s physicochemical properties, crucial for consistent high-quality cheese production.