|
| S. No | Drying method(s) | Tem (°C) | Duration | MC (%) | pH | Fat (%) | Shell content | Other quality parameters analyzed | References |
| BD | AD |
|
| Set standards (reference values) | ≤60 | Varied | NA | 5.5-8 | 3.8-5.5 | 55-56 | 15-17% | Bean colour, antioxidant activity, phenolic compounds, OTA, titratable acidity, acetic acid, PAH, mouldiness, theobromine, caffeine, dry bean recovery rate, foreign matter, bean count, sound of dry grain, ordour, separation of husk | [4, 7, 30] |
|
| (a) Open sun drying methods | | | | | | | | | |
| 1 | Direct sun dryer (wooden platform) | >60 | 7 d | 52.2 | 8.03 | NA | NA | NA | Antioxidant activity, phenolic compound content (catechin and methylxanthines), OTA | [1] |
| 2 | Open sun drying | NA | 20 h | 67 | 8.6 | NA | NA | NA | Bean colour, dust, dirt, and other pollutants | [47] |
| 3 | Sun drying on raised bamboo mats | NA | 8 d | 53.16 | 5.5 | 6.7 | NA | NA | Bean colour, titratable acidity, ash content | [48] |
| 4 | Open sun-drying with tempering | 30.2 to 37.8 °C | 60 h | NA | ≤23 | 5.37–5.39 | NA | NA | Bean colour, fat content, crude protein, carbohydrates | [49] |
| 5 | Open sun drier | NA | 40 h | 57 | 6.5 | NA | NA | NA | Bean colour, flavour | [50] |
| 6 | Open sun drying | NA | NA | NA | NA | NA | NA | NA | μg·kg-1 | [51] |
| |
| 7 | Open sun drying on black tarpaulin and bamboo mats. | NA | 10 d | 53.5 | 5.49 | 5.9 | NA | NA | Polyphenol content, mould infection, bean colour, and OTA | [8] |
| 8 | Open sun drying | NA | NA | 50 | 7 | 5.18 | NA | NA | Total amino acid content, total sugar reduction, ordour | [52] |
| Combined sun and tunnel dryer | 18 h | 5.58 |
| 9 | Full sun drying | NA | 2-5 d | | 7.5 | NA | NA | NA | PAH | [15] |
| 10 | Sun drying on rack tables, concrete floor, black tarpaulins | NA | NA | NA | 7.5 | NA | NA | NA | OTA ( mg/kg) | [36] |
| 11 | Open sun drying | NA | NA | 53.7 | 6.97 | 6.9 | NA | NA | FFA, acetic acid | [14] |
| 12 | Open sun drying | NA | NA | 53.7 | 7-8 | 5 | NA | NA | Volatile acidity, free acidity | [32] |
| Mixed sun & oven drying | 4.5 |
| 13 | Open sun drying | NA | 30 h | 49.9 | 7-8 | 5.1 | NA | NA | Bean colour, titratable acidity, acetic acid, & free fatty acid | [31] |
| 14 | Direct sun dryer (wooden platform) | >60 | 7 d | 52.2 | 8.03 | NA | NA | NA | Antioxidant activity, phenolic compound content (catechin and methylxanthines), OTA | [1] |
| Mixed dryer (plastic roof without UV protection and exposure to sun light) | >60 | 49.4 | 7.5 |
|
| (b) Solar drying methods | | | | | | | | | | |
| 1 | Solar greenhouse dryer | 30.9 | 7 d | | 5.7 | 5.2 | 50 | 12.1 | Dry bean recovery rate, foreign matter, bean count, bean colour, brown fat | [4] |
| 2 | Greenhouse dryer (plastic roof with UV protection) | 60 | 7 d | 52.2 | 8.1 | NA | NA | NA | Antioxidant activity, phenolic compound content (catechin and methylxanthines), OTA | [1] |
| >60 | 6.9 |
| Dryer with wooden platform | 60 | 7.76 |
| Mixed dryer (plastic roof without UV protection and exposure to sun light) | >60 | 49.4 | 7.5 |
| 3 | Cocoa house replica dryer | 31-35 | 4.8d | 50.9 | 6-8 | 5.46–4.97 | NA | NA | Bean colour, water activity, cocoa flavour, total acidity, bitterness, astringency | [53] |
| Greenhouse dryer | 6.3d |
| 4 | Heated batch cocoa bean dryer | 55 | 6 h | 79.6 | 6 | NA | NA | NA | NA | [34] |
| 70 | 5 h | |
| 81 | 4 h |
| 5 | Forced-air, artificial intermittent dryer | 35, 40, 45, 50, & 55 | NA | NA | NA | 4.7-5.2 | NA | NA | Free fatty acid, acetic acid levels | [54] |
| 6 | Solar tunnel heat pump dryer | 29.6-48.8 | 20 h | 67 | 8.6 | NA | NA | NA | Bean colour, dust, dirt, and other pollutants | [47] |
| 7 | Solar drying | NA | 8D | 53.6 | 4.8 | 6.9 | NA | NA | Bean colour, titratable acidity, ash content | [48] |
| 8 | Tunnel dryer | 50,55,60, 65, 70, 75,80, & 85 | NA | NA | 7-4.9 | 6.08-5.7 | 12.02-10.12 | NA | Protein (%), fibre, ash, & CHO | [55] |
| 9 | Solar dryer for intermittent convection | 31-54 | 72 h | 53.4 | 3.6 | 5.18 | NA | NA | Acid value, bean colour, bitterness, mouldiness, free fatty acid level, moisture reabsorption rate | [16] |
| Solar dryer for intermittent drying +natural convection | NA | NA | NA | 6.35 |
| 10 | Solar dryer with adsorbent | 40-54 | 41 h | NA | NA | NA | NA | NA | Weight stability | [56] |
| Solar dryer with absorbent | 30 h |
| 11 | Oven drying with curing of 24 h after 3 hours of continuous drying | 60 | 52 h | NA | 13–14 | 5.37–5.39 | NA | NA | Bean colour, fat content, crude protein, carbohydrates | [49] |
| 12 | Mobile solar dryer | NA | 32 h | 57 | 6.5 | NA | NA | NA | Bean colour, flavour | [50] |
| 13 | Rotary dryer equipped with an electric heater and infrared lamps | 50 | 9.25 h | 56 | 7 | NA | NA | NA | Polyphenols, caffeine, theobromine, epicatechin and catechin content | [6] |
| 55 | 8.5 h |
| 60 | 7.1 h |
| 14 | Mechanical (tunnel) dryer | 60 | NA | 50 | 7 | 5.46 | NA | NA | Total amino acid content, total sugar reduction, ordour | [51] |
| 15 | Indirect heavy load solar dryer | 40-70 | 7 d | 55 | 7.5 | NA | NA | NA | Titratable acidity, bean colour, ordour | [57] |
| 16 | Integrated solar dryer with adsorbent desiccant | NA | 30 h | 56.4 | 6.3 | NA | NA | NA | Mouldiness, bean colour, sound of dry grain, ordour, separation of husk | [41] |
| Polycarbonate tunnel solar dryer (equipped with electric fans) | 24 h |
| Integrated solar dryer with absorbent desiccant | 19 h |
| 17 | Solar drying | NA | 9 h | 58 | 13-14 | NA | NA | NA | NA | [38] |
| Sweat box drying (100 W bulb) | 9 h |
| Sweat box drying (200 W bulb) | 8 h |
| Sweat box drying (300 W bulb) | 7 h |
| Sweat box drying (400 W bulb) | 6 h |
| 18 | Direct solar dryer at three levels of loading | 20 kg | 5 d | 54 | 7.5 | 5.1 | NA | NA | Mouldiness, titratable acidity | [37] |
| 30 kg | 7 d | | | 4.9 |
| 60 kg | 9 d | | | 5.4 |
| 19 | Tray dryer | NA | 8 h | 49.9 | 6.4 | 5.2 | NA | NA | Bean colour, titratable acidity, acetic acid, & free fatty acid | [31] |
| Solar cabinet dryer, | 16 h | 49.4 | 7.6 | 6.3 |
| 20 | Greenhouse dryer (plastic roof with UV protection) | 60 | 7 d | 52.2 | 8.1 | NA | NA | NA | Antioxidant activity, phenolic compound content (catechin and methylxanthines), OTA | [1] |
| >60 | 6.9 |
| Dryer with wooden platform | 60 | | | 7.76 | | | | | |
|
| (c) Oven drying method | | | | | | | | | | |
| 1 | Mechanical oven | 40 | 4.3d | 50.9 | 6-8 | 5.46-4.97 | NA | NA | Bean colour, water activity, cocoa flavour, total acidity, bitterness, astringency | [53] |
| 2 | Humidity controlled dryer chamber (laboratory oven) | 60 | 12, 24, 32, & 40 h | NA | NA | NA | NA | NA | Polyphenol contentment, astringency, flavour, bitterness | [58] |
| 3 | Wood smoke | NA | NA | NA | NA | NA | NA | NA | | [51] |
| 4 | Oven drying | 60-80 | 12-40 h | 55 | 7.5 | NA | NA | NA | Polyphenol content | [59] |
| Adsorption drying | 60 | 24 h |
| Vacuum drying | 60 | 24 h |
| 5 | Full electric oven | 80 | 2-5 d | | 7.5 | NA | NA | NA | PAH | [15] |
| 6 | Oven drying | 35 | 39 h | 53.7 | 6.85 | 6.7 | NA | NA | FFA, acetic acid | [14] |
| 40 | | 6.75 | 6.1 |
| 45 | 33 h | 6.70 | 5.8 |
| 50 | | 6.62 | 4.9 |
| 55 | 18 h | 5.3 | 4.5 |
| 7 | Oven drying | 60 | NA | 53.7 | 7-8 | 4.5 | NA | NA | Volatile acidity, free acidity | [32] |
|
| (d) Microwave and freeze drying methods | | | | | | | | | | |
| 1 | Microwave drying | 3200 W | 8 mins | 53.5 | 5.60 | NA | NA | NA | NA | [44] |
| 2800 W | 12 mins | 5.63 |
| 2400 W | 16 mins | 5.77 |
| 2 | Freeze drying (fresh beans blanched at 90°C for 5 minutes) | -30°C | 24 h | 55 | 7.5 | NA | NA | NA | Polyphenol content | [59] |
| -50°C | 4 h |
| Vacuum drying | 60 | 24 h |
| 3 | Domestic microwave oven | 600 W | 250 sec | 56.4 | 7 | NA | NA | NA | NA | [46] |
| 300 W | 350 sec |
| 150 W | 450 sec | 6.6 |
| 4 | Microwave oven | NA | 0.4 h | 49.9 | 7.1 | 7.2 | NA | NA | Bean colour, titratable acidity, acetic acid, & free fatty acid | [31] |
|
