Effect of harvest year on the physical properties, chemical composition and cooking time of three common bean varieties that are grown in Mexico

It is important to consider the physical properties of legume seeds in the design of bean storage and processing systems. The variation in the physical properties of three common bean (Phaseolus vulgaris L.) varieties (Bayo Victoria (BV), Negro San Luis (NSL) and Pinto Saltillo (PS)) according to harvest year (2008 and 2010) was studied. Harvest year and variety affected (P<0.05) the following tested variables: 100-grain weight, hardness, water absorption capacity, length, width, thickness, arithmetic diameter, geometric diameter, surface area, volume, sphericity, chemical composition, and cooking time. Weight ranged from 27.72 to 50.39 g among the three varieties. BV exhibited the highest weight (50.39 g), length (14.75 mm), width (9.52 mm in 2008; 9.09 mm in 2010), thickness (6.40 mm in 2008; 6.34 in 2010) and surface area (293.69 mm2). Hardness was highest in NSL and PS in 2008 (181.1 N) and lowest in BV and NSL in 2010 (103.23 N). Hardness in BV and NSL did not differ (P>0.05) between years. Sphericity was highest overall in NSL (70.97% in 2008; 68.91% in 2010). Moisture content was highest in NSL and PS (11.76 g H2O/100 g). In all varieties, moisture content was higher in 2008 than in 2010, although this was not significant (P>0.05). Harvest year affected (P<0.05) protein, crude fibre, ash and carbohydrate content. The highest protein content was found in BV. Varieties harvested in 2008 had the highest cooking time according to default hard-to-cook development during storage; however, PS was unaffected by harvest year and presented the shortest cooking time.