Abstract
Despite increased consumer interest in organic produce, little is known about how different organic production methods affect both the traditional measures of quality and the naturally occurring health promoting (bioactive) compounds of food. In this study, “Obsidian” and “Triple Crown” blackberries (bothRubushybrids) were cultivated organically and fertilized with either soy meal, fish emulsion/hydrolysate blend, or processed poultry litter fertilizers at a fixed rate. Fruits were hand-harvested three times during their peak production period and stored at 4°C and 85% RH for up to 12 d. Fertilizer effects on the physicochemical properties were minor, while harvest period had a stronger effect, though that trend varied by year. Antioxidant and sugar profile data revealed an interesting pattern: “Obsidian” had ORAC and lower sugar than “Triple Crown” at harvest and also had greater differentiation due to fertilizer treatments. Fertilizer effects differed based on harvest date and cultivar, with late harvest fruit fertilized with fish emulsion fertilizer showing higher TPC and ORAC than other fertilizer treatments, while the early and middle harvest fruit showed similar or greater responses to soy meal-based fertilizer. Time of harvest and length of storage also affected the antioxidant properties and sugar profiles in different ways depending on fruit cultivar, again with the “Obsidian” fruit showing greater variability in general. This study demonstrated that the two cultivars of organically grown blackberry fruit have different physicochemical and antioxidant properties, thus potentially different shelf lives in the fresh market.
Highlights
Consumer interest in organic produce has resulted in the rapid growth of organic agriculture in the US, with total acreage of organic crops increasing 253% between 2000 and 2011, and the previous year data are available from USDA [1]
Decay rates for the two cultivars ranged 5.56–54.86% in 2012 and 0.74–46.89% in 2013, with “Triple Crown” having higher decay rate in 2012 and “Obsidian” having higher decay rate in 2013; though in the former case, it should be noted that the “Triple Crown” storage time was twice as long as the “Obsidian.” Examining the effect of storage time on decay showed decay rates tending to increase with prolonged storage, which was fairly predictable, given that the decay of blackberries is usually caused by fungal growth, and Botrytis cinerea, the primary fungal disease of ripe blackberry fruit, can continuously grow at low temperatures [33, 43]
Rain during or immediately prior to harvest can result in significant fruit decay due to favorable mold growth conditions, and high temperature and high UV index may result in advanced ripening which leads to loss of firmness and greater fruit leakage [44, 45]
Summary
Consumer interest in organic produce has resulted in the rapid growth of organic agriculture in the US, with total acreage of organic crops increasing 253% between 2000 and 2011, and the previous year data are available from USDA [1]. Even among different types of organic fertilizer, great variability was found in horticultural measures of performance, such as yield and nitrogen uptake [18, 19] It is unknown how the different organic fertilizer sources can affect the overall fruit quality, a question that needs to be answered, given that Bulluck et al [20] showed that different organic fertilizer sources affect crop yield and modify the physical, chemical, and microbial properties of the soil itself and in turn the quality of fruit [21,22,23,24]
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