Table 2.
Batch‐to‐batch analysis of the NF produced under acidic conditions
| Parameter | Batch number | Method of analysis | ||||
|---|---|---|---|---|---|---|
| #1‐A | #2‐A | #3‐A | #4‐A | #5‐A | ||
| Physico‐chemical parameters | ||||||
| Insolubility index (mL) | 0.09 | 0.09 | 0.09 | 0.09 | 0.09 | ISO 8156:2005/IDF 129:2005 |
| pH (10% solution) | 3.7 | 3.8 | 3.7 | 3.8 | 3.8 | ISO 5546:2010/IDF 115:2010 |
| Composition | ||||||
| Protein ‘as is’ (N × 6.38) (%) | 92.13 | 91.14 | 92.30 | 91.67 | 92.94 | Kjeldahl; ISO 8968‐3:2004/IDF 20‐3:2004 |
| Protein in DM (N × 6.38) (%) | 95.43 | 94.63 | 95.85 | 95.21 | 96.23 | Calculation (1) |
| BLG (2) (% of protein) | 100.97 | 103.00 | 104.69 | 106.29 | 102.65 | RP‐HPLC/UV (validated internal method) |
| Lactose (%) | 0.09 | 0.09 | 0.09 | 0.09 | 0.09 | Enzymatic; ISO 5765‐2/IDF 79‐2:2002 |
| Fat (%) | 0.06 | 0.06 | 0.11 | 0.22 | 0.09 | Gravimetry; ISO 1736/IDF 9:2008 |
| Ash (%) | 0.14 | 0.09 | 0.09 | 0.09 | 0.09 | Gravimetry; NMKL 173:2005 |
| Moisture (%) | 3.46 | 3.69 | 3.70 | 3.72 | 3.42 | Gravimetry; ISO 6731:2010/IDF 21:2010 |
| Minerals | ||||||
| Aluminium (mg/kg) | < 0.5 | 0.6 | < 0.5 | < 0.5 | < 0.5 | EN ISO 17294‐2‐E29 (DE Food)/ICP‐MS |
| Chromium (mg/kg) | – | – | 0.32 | < 0.20 | < 0.20 | DS/EN 13805m:2014, DS/EN ISO 17294m:2016/ICP‐MS |
| Chloride (%) | 1.53 | 1.45 | 1.61 | 1.52 | 1.52 | Potentiometric titration; ISO 5943:2006/IDF 88:2006 |
| Calcium (%) | 0.025 | 0.025 | 0.025 | 0.025 | 0.025 | ICP (internal method) |
| Magnesium (%) | 0.003 | 0.003 | 0.003 | 0.003 | 0.003 | ICP (internal method) |
| Phosphorus (%) | 0.025 | 0.025 | 0.025 | 0.025 | 0.025 | ICP (internal method) |
| Potassium (%) | 0.025 | 0.025 | 0.025 | 0.025 | 0.025 | ICP (internal method) |
| Sodium (%) | 0.025 | 0.025 | 0.025 | 0.025 | 0.025 | ICP (internal method) |
| Contaminants | ||||||
| Arsenic (mg/kg) | < 0.01 | < 0.01 | < 0.01 | < 0.01 | < 0.01 | DS/EN 13805m:2014, DS/EN ISO 17294m:2016/ICP‐MS |
| Cadmium (mg/kg) | < 0.01 | < 0.01 | < 0.01 | < 0.01 | < 0.01 | ICP‐MS ISO 17294‐2:2016 |
| Lead (mg/kg) | < 0.003 | < 0.003 | < 0.003 | < 0.003 | < 0.003 | ICP‐MS ISO 17294‐2:2016 |
| Mercury (mg/kg) | < 0.005 | < 0.005 | < 0.005 | < 0.005 | < 0.005 | ICP‐MS ISO 17294‐2:2016 |
| Aflatoxin M1 (µg/kg) | < 0.01 | < 0.01 | < 0.01 | < 0.01 | < 0.01 | HPLC‐FLD (internal method) |
| Microbial parameters | ||||||
| Total plate count (CFU/g) | < 10 | < 10 | 110 | 20 | < 10 | ISO 4833‐1:2013 |
| Yeast and mould (CFU/g) | < 10 | < 10 | < 10 | < 10 | < 10 | ISO 6611:2004/IDF 94:2004 |
| Enterobacteriaceae (CFU/g) | < 10 | < 10 | < 10 | < 10 | < 10 | ISO 21528‐2:2017 |
| Salmonella (in 25 g) | ND | ND | ND | ND | ND | ISO 6579 |
| Bacillus cereus (CFU/g) | 140 | 80 | 10 | < 10 | 50 | ISO 7932:2004 |
| Listeria monocytogenes (in 25 g) | ND | ND | ND | ND | ND | ISO 11290 |
| Staphylococcus aureus (CFU/g) | < 10 | < 10 | < 10 | < 10 | < 10 | ISO 6888‐1:1999/Amd.1:2003 |
| Sulfite‐reducing clostridia (CFU/g) | < 10 | < 10 | < 10 | < 10 | < 10 | ISO 15213:2003 |
‘–’: Not reported; ‘A’: NF produced under acidic conditions; ADPI: American Dairy Products Institute; Amd.: Amendment; BLG: Beta‐lactoglobulin; CFU: Colony forming unit; DE Food: German Food and Feed Code; DM: Dry matter; DS: Danish standard; EN: European norm; ICP: Inductively coupled plasma; IDF: International Dairy Federation; ISO: International Organisation for Standardisation; HPLC/FLD: High‐performance liquid chromatography with fluorescence detection; MS: Mass spectrometry; ND: Not detected; NMKL: Nordic Committee on Food Analysis; RP‐HPLC/UV: Reversed phase‐high performance liquid chromatography with UV detection.
Protein in DM = (Protein ‘as is’/DM) × 100%.
The levels of BLG, expressed as % of the total protein, exceed 100% in some batches, which can be attributed to the uncertainty of the method (RP‐HPLC/UV) used for the quantification of BLG using a commercial standard with 90% purity.