Currently, fresh market apples are harvested manually in the U.S. and around the world. Because of increasing labor shortages and costs, there is a critical need for developing mechanical harvesting techniques. Mass harvest using a shake-And-catch system is a potential solution for addressing this issue. Selecting suitable materials that can provide adequate cushioning for apples could help to reduce fruit bruising during mechanical harvesting. To gain an understanding of how cushioning materials can absorb impacts on fruit, an experimental study was conducted to investigate the bruise response of apples to different impact levels. A specially designed pendulum impact platform was used to conduct the tests. Three types of cushioning materials (polyurethane foam) covering an aluminum plate were used as the impact surfaces, and the bare aluminum plate was used as the control surface. Polyurethane foams with the same thickness but different firmness ratings (at 25% deflection) were used to exert impacts on stationary apples sitting freely on a horizontal surface. In this study, seven different impact levels were applied at three impact zones (top, middle, and bottom) of 'Jazz' apples. Impact tests were repeated 50 times for each impact level at each zone. The results showed that no bruising resulted when apples were impacted at 22 N with the bare aluminum plate regardless of the impact zone. The non-bruising impact level increased to 95, 160, and 160 N after 12.7 mm thick foam cushions with firmness ratings of 2.1, 4.8, and 9.7 to 11 kPa (foams 1, 2, and 3, respectively) were used to cover the aluminum plate. Based on USDA grades, 100% of the apples maintained Extra Fancy quality at 50, 115, 171, and 180 N when impacted by the bare aluminum plate and by the plate covered with foams 1, 2, and 3, respectively. The tolerable impact levels to maintain 100% of apples within the fresh-market quality threshold were 95, 189, 230, and 232 N, respectively. These results showed that the foams with firmness ratings of 4.8 kPa and 9.7 to 11.0 kPa (foams 2 and 3) provided better cushioning for apples, as the fruit tolerated a substantially higher level of impact compared to using the bare aluminum plate or foam 1. The results also showed that the difference between foams 2 and 3 was very slight, which could indicate that a cushioning material with a firmness rating of 4.8 kPa or higher could provide sufficient cushioning for apples.
All Science Journal Classification (ASJC) codes
- Food Science
- Biomedical Engineering
- Agronomy and Crop Science
- Soil Science