Bhawana Bhattarai

The biochemistry underlying seed coat darkening of lentil due to extended storage is limited. This study investigated the relationship between seed coat darkening over time during storage and changes in concentration of phenolic compounds (total phenolic compounds, total condensed tannins, proanthocyanidins and anthocyanins) in two red lentil cultivars (PBA Hallmark and PBA Jumbo2), stored at two grain moisture contents (10 and 14%, w/w) and two temperatures (4 and 35 °C) for 360 days. Seed coat darkening was only significant (p = 0.05) at high temperatures (35 °C) but not at low temperatures (4 °C), irrespective of grain moisture content and cultivar. The concentration of all phenolic compounds tested in this study reduced significantly (p = 0.05) throughout the study period, regardless of temperature and grain moisture treatments. The changes in seed coat brightness and redness followed a linear pattern, except for yellowness, where phenolic compounds initially reduced linearly and then remained constant thereafter. Darkening of seedcoat was only associated with the reduction in phenolic compounds tested in this study at 35 °C, and not at 4 °C. This suggests that seed coat darkening due to extended storage may not be directly linked to broad reductions in the groups of phenolic compounds or individual compounds assessed in this study. This information prompts further research to identify the actual biochemical processes that cause the darkening of seed coats during storage and assist in developing cultivars with stable seed coat colour by selecting and modifying such processes.

This study presents an explanatory biophysical model developed and validated to simulate seed coat colour traits including CIE L*, a*, and b* changes over time for stored lentil cultivars PBA Hallmark, PBA Hurricane, PBA Bolt, and PBA Jumbo2 under diverse storage conditions. The model showed robust performance for all cultivars, with R² values ≥ 0.89 and RMSE values ≤ 0.0019 for all seed coat colour traits. Laboratory validation at 35 °C demonstrated a high agreement (Lin’s Concordance Correlation Coefficient, CCC ≥ 0.82) between simulated and observed values of all colour traits for PBA Jumbo2 and strong agreement (CCC ≥ 0.81) for PBA Hallmark in brightness (CIE L*) and redness (CIE a*), but not in yellowness (CIE b*). At 15 °C, both cultivars exhibited moderate to weak agreement between simulated and observed values of all colour traits (CCC ≤ 0.47), as very little change was recorded in the observed values over the 360 days of storage. Bulk storage system validation for PBA Hallmark showed moderate performance (CCC ≥ 0.46) between simulated and observed values of all colour traits. Modelling to simulate changes in seed coat colour traits of lentils over time will equip growers and traders to make informed managerial decisions when storing lentils for long periods.

Storing lentil is a strategy used by growers to manage price volatility. However, studies investigating the impact of storage conditions on the market and end use properties of lentil are limited. This study examined the effects of storage temperature (4, 15, 25, and 35 °C) and grain moisture (10 and 14%, w/w) on traits related to market (seed coat colour), viability (germination capacity), and end use properties (hydration capacity, milling efficiency, and cooking quality) in four red lentil cultivars (PBA Bolt, PBA Hallmark, PBA Hurricane, PBA Jumbo2) over 360 days. Storing lentil at 14% moisture content and 35 °C significantly (p = 0.05) darkened seed coat after 30 days, caused complete loss of viability within 180 days and reduced cooking quality (cooked firmness) after 120 days across all tested cultivars. Storing lentil at 10% moisture content and 35 °C reduced hydration capacity after 30 days, and milling efficiency after 120 days across all cultivars tested. PBA Jumbo2 exhibited a higher rate of degradation in hydration capacity and cooking quality, and a lower rate of degradation in the other traits studied. Storing lentil at ≤15 °C prevented degradation of all quality traits. These findings will support improved lentil storage protocols to maintain quality and improve economic outcomes for the pulse industry.

Lentil seed coat colour influences market value, whilst germination is associated with crop establishment and hydration capacity with optimal processing outcomes. Storing lentil grain assists growers in managing price fluctuations; however, exposure to oxygen at higher temperatures during extended storage degrades seed coat colour, germination, and hydration capacity. Depleting oxygen prevents such degradation in other crops; however, studies in lentil are limited. This study examined the effects of oxygen-depleted modified atmospheres and temperatures on seed coat colour, germination, and hydration capacity in two red lentil cultivars, PBA Hallmark and PBA Jumbo2, stored for 360 days. Small volumes of lentil grain were placed in aluminium laminated bags filled with nitrogen (N₂), carbon dioxide (CO₂), or air and stored at either 15 or 35 °C. At 35 °C in an air atmosphere, the lentil’s seed coat significantly (p = 0.05) darkened after 30 days of storage, whereas germination and hydration capacities decreased after 60 days regardless of cultivar. In contrast, N₂ and CO₂ atmospheres maintained initial seed coat colour, germination, and hydration capacities in both cultivars throughout the study period regardless of temperature. Storing lentil grain in an oxygen-depleted modified atmosphere may assist to maximise returns to grower and maintain key quality traits.