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Fig. 4.
Chemical, organoleptic, and microbiological parameters of sheepskins treated with NaCl
| Name of indicator | Sheepskin processing options | Normative documentation on research methods | |||
|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | ||
| Organoleptic indicators | |||||
| Appearance | The hairline of the skin is slightly damp. The skin is soft, not elastic | The hairline of the skin is dry. There is some moisture at the junction of the skin and hair. The skin is elastic | The hairline of the skin is dry. The skin is elastic | The hairline of the skin is dry. There are places with a small touch of salt. The skin is elastic | GOST 28509-90. Leather raw material. Sheepskins are undressed. Specifications |
| Mezdra (a layer of subcutaneous fatty tissue, meat, fat, and pieces of tendons that are removed from the skin in the process of preparatory operations) color | Mezdra gray shade | Mezdra light milky color | Mezdra light milky color | Mezdra with a milky yellow tint | |
| Chemical indicators | |||||
| NaCl concentration, g/l | 70 (20% of saturated solution) | 100 (30% of saturated solution) | 125 (40% of saturated solution) | 150 (50% of saturated solution) | GOST 13105-77 Leather raw materials. Methods for determining the components of preserving |
| Moisture, % | 17,8 | 16,2 | 15,5 | 15,1 | GOST 13104-77. Leather raw material. Methods for determining salt and net weight |
| NaCl, % | 6,7 | 10,6 | 11,7 | 12,8 | GOST 13105-77 Leather raw materials. Methods for determining the components of preserving |
| pH | 5,4 | 5,1 | 4,9 | 4,7 | GOST 32165-2013. Dressed fur and sheepskin skins. Method for determining the pH of an aqueous extract |
| microbiological indicators | |||||
| QMAFAnM, CFU/g | 5×102 | 6×102 | 2×102 | 2×102 | GOST 25311-82. Feed flour of animal origin. Methods of bacteriological analysis. GOST 26670-91. Food products. Methods of cultivation of microorganisms. GOST 10444.15-94. Food products. Methods for determining the number of mesophilic aerobic and facultative anaerobic microorganisms |
| Mold, CFU/g | 1 | Not detected | Not detected | Not detected | |
| Halophiles | Not detected | Not detected | Not detected | Not detected | |
Organoleptic and physico-chemical parameters of combined whey
| Name of indicator | Combination serum options | Normative documentation on research methods | |||
|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | ||
| Appearance and texture | Homogeneous translucent liquid with the presence of a protein precipitate | The determination of organoleptic indicators is carried out visually and organoleptically at a whey temperature of (22 ±2) °C according to GOST 343522017 “Whey - raw materials. Specifications» | |||
| Color | Pale green | ||||
| Taste and smell | Characteristic of whey, sour | ||||
| Mass fraction of fat, % | 0,4 | 0,2 | 0,2 | 0,3 | GOST 5867-90 “Milk and dairy products. Methods for determining fat « |
| Mass fraction of solids, % | 5,1 | 5,7 | 5,4 | 5,9 | GOST 33957-2016 “Whey and drinks based on it. Acceptance rules, sampling and control methods» |
| Density, kg/m3 | 1025 | 1024 | 1026 | 1028 | |
| Titratable acidity, °T | 88 | 90 | 87 | 91 | |
| Active acidity, pH | 3,96 | 3,85 | 3,98 | 3,98 | |
| Temperature, °C | 6±2 | 6±2 | 6±2 | 6±2 | |
Microbiological indicators of sheepskins after 5,7,10 and 15 days of preservation
| Experienced options | Sheepskins after preservation | |
|---|---|---|
| QMAFAnM, CFU/g | mold, CFU/g | |
| Sheepskins after 5 days of preservation | ||
| paired | 8×106 | 30 |
| 1 option (20%) | 14×103 | 18 |
| 2 option (30%) | 12×103 | 10 |
| 3 option (40%) | 9×103 | 2 |
| 4 option (50%) | 5×103 | 1 |
| Control | 13×103 | 16 |
| Sheepskins after 7 days of preservation | ||
| 1 option (20%) | 3×103 | 18 |
| 2 option (30%) | 2×103 | 10 |
| 3 option (40%) | 1,2×103 | 2 |
| 4 option (50%) | 1,1×103 | 1 |
| Control | 5×103 | 19 |
| Sheepskins after 10 days of preservation | ||
| 1 option (20%) | 2×103 | 20 |
| 2 option (30%) | 2×103 | 12 |
| 3 option (40%) | 1×103 | 2 |
| 4 option (50%) | 1×103 | 1 |
| Control | 3×103 | 20 |
| Sheepskins after 15 days of preservation | ||
| 1 option (20%) | 1,1×103 | 24 |
| 2 option (30%) | 1,3×103 | 13 |
| 3 option (40%) | 9×102 | 3 |
| 4 option (50%) | 5×102 | 2 |
| Control | 1×103 | 26 |
Microbiological parameters of combined whey
| Name of indicator | Norm according to normative documentation | Actual performance | Normative documentation on research methods |
|---|---|---|---|
| Quantity of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM), CFU/g | no more than 1×105 | 3,9×104 - 6,5×104 | GOST 34352-2017. Whey - raw material. Specifications |
| Bacteria of the Escherichia coli group (Coliform bacteria) in 0.1 g | not allowed | not detected | |
| Pathogenic, including salmonella in 25 g | not allowed | not detected | |
| S. aureus in 0.1 g | not allowed | not detected | |
| Yeast, CFU/g | not allowed | not detected | |
| Molds, CFU/g | not allowed | not detected |
Dynamics of the temperature of the leather tissue shrinkability during storage for 15 days after salting in the experimental curing mixture and in the control curing liquid
| Indicators | Shrinkage temperature of leather tissue by days of storage in experimental batches and control | |||
|---|---|---|---|---|
| 5 days | 7 days | 10 days | 15 days | |
| Experimental variant 1 - (20 %) (n=8) | ||||
| M | 67,13 | 67,75 | 64,75 | 67,88 |
| ±δ | 0,22 | 0,38 | 0,38 | 0,22 |
| CV (%) | 0,33 | 0,56 | 0,59 | 0,32 |
| Experimental variant 2 - (30 %) (n=8) | ||||
| M | 67,25 | 67,88 | 67,13 | 64,13 |
| ±δ | 0,38 | 0,22 | 0,22 | 0,22 |
| CV (%) | 0,57 | 0,32 | 0,33 | 0,34 |
| Experimental variant 3 - (40 %) (n=8) | ||||
| M | 67,5 | 68,13 | 67,63 | 68,88 |
| ±δ | 0,5 | 0,22 | 0,47 | 0,22 |
| CV (%) | 0,74 | 0,32 | 0,69 | 0,32 |
| Experimental variant 4 - (50 %) (n=8) | ||||
| M | 66,88 | 63,63 | 68,5 | 66,63 |
| ±δ | 0,22 | 0,47 | 0,5 | 0,47 |
| CV (%) | 0,33 | 0,74 | 0,73 | 0,71 |
| Control (n=8) | ||||
| M | 67,13 | 62,63 | 62,88 | 62,13 |
| ±δ | 0,22 | 0,47 | 0,22 | 0,22 |