Anthocyanin Levels in Nine Lettuce (Lactuca sativa) Cultivars: Influence of Planting Date and Relations among Analytic, Instrumented, and Visual Assessments of Color

Abstract

<jats:p>Leaf samples collected from field plots of nine lettuce cultivars established in the early (ES) and late (LS) summer of 2002 and 2003 in Celeryville, Ohio, were subjected to spectrophotometric measurement of anthocyanin concentrations or color analysis based on colorimeter and spectroradiometer readings and human panelist ratings. Interactions among year (Y), transplanting date (TD), and cultivar (C) main effects for anthocyanin concentration were significant as a result of shifts in response magnitude but not direction. Anthocyanin levels were higher after LS than ES transplanting regardless of Y and C. The effects of TD were pronounced in 2002, when differences in average daily temperature between ES and LS transplantings tended to be larger. Also, regardless of Y and TD, anthocyanin levels followed the pattern ‘Impuls’ &gt; ‘OOC 1441’ &gt; ‘Valeria’ &gt; ‘OOC1426’ &gt; ‘Lotto’ &gt; ‘SVR 9634’ &gt; ‘OOC 1434’ = ‘OOC 1310’ &gt; ‘Cireo’. Treatment-based color differences were also evident in colorimeter and spectroradiometer readings. Also, panelists differentiated samples grown in 2003 based on red color intensity. Correlations between analytic and instrumented and human panelist-based measures suggest instrumented assessments of red coloration may serve as proxies for direct measures of anthocyanin levels or human panelist ratings, particularly if the aim is to establish color differences between major experimental groups and assign quantitative, repeatable values to red color intensity.</jats:p>

Non-destructive Phenotyping of Lettuce Plants in Early Stages of Development with Optical Sensors

“…Panelists, however, could not determine red color in a cultivar with a low anthocyanin level. Similarly, we have detected anthocyanin through hyperspectral analysis in the leaf samples with the ‘no red’ color rating, confirming that the threshold level of anthocyanin needed for the detection by visual observation is higher than is the actual level of anthocyanin in some lettuces (Gazula et al, 2007). …”

“…Hence, the breeders selecting for dark red color (high RAC) may consider temporarily subjecting lettuce plants to low temperatures where differences among genotypes are likely to be more pronounced (assuming that the pattern of changes in pigments is the same as in our study). These results are somewhat unexpected, because several previous studies reported that low temperatures lead to increased anthocyanin production in lettuce (Gazula et al, 2005, 2007; Boo et al, 2011; Chon et al, 2012; Becker et al, 2014a). However, when the regulation of anthocyanin biosynthesis [quantified as cyanidin-3- O -( 6 ″-malonyl)-glucoside] was compared in three cultivars, a substantial difference in their response to varying temperatures was detected.…”

“…We have determined that the visual rating of the green and red leaf color is strongly associated with the values of RCC and RAC obtained from hyperspectral imaging ( Figure 2 ). Previously, a good correlation ( r = 0.76) was found between the ratings of lettuce red color intensity performed by human panelists and the direct measurements of anthocyanin levels (Gazula et al, 2007). Panelists, however, could not determine red color in a cultivar with a low anthocyanin level.…”

Spectral quality of photo-selective nets improves phytochemicals and aroma volatiles in coriander leaves (Coriandrum sativum L.) after postharvest storage

“…Ultimately, the quality of herbs is mainly defined in terms of consumer acceptability, which is mostly based on appearance such as freshness, uniformity of size and shape, right maturity, right colour, freedom from defects (such as rot, physical damage and yellowing or wilting), flavour and aroma [5]. The quantity and distribution of chlorophylls contribute significantly to the leaf colour and product appeal [6]. Postharvest overall quality, phytochemical composition and storage life are influenced by the environment and cultural practices; these include seasonal growing temperatures, light conditions, the amount of rainfall and irrigation, mineral nutritional status and fertilisation, pest management, and maturity at harvest time.…”

In vitro evaluation of red and green lettuce (Lactuca sativa) for functional food properties

“…The antioxidant phenolics in lettuce vary amongst varieties due to growing practices, processing and storage conditions (Baur, Klaiber, Koblo, & Carle, 2004). Currently, red lettuce is popular in salad mixes due to its anthocyanin content that contributes to the higher value it fetches compared to the green lettuce (Gazula, Kleinhenz, Scheerens, & Ling, 2007). The increased demand of fresh vegetables associated with health benefits has led to an increase in the quality, quantity and variety of produce available to the consumer.…”