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Purple cabbage is one of the world's most widely consumed vegetables with high nutritional values containing the antioxidants and anti‐inflammatory activity of anthocyanins, vitamins, and minerals. But due to rapid postharvest quality decay, novel processing techniques including drying are required. In order to determine the conditions of combined microwave and hot air drying for purple cabbage, factors affecting the drying process including microwave density, hot air temperature, and the dry base water content at conversion point were investigated using the anthocyanin content, DPPH antioxidant capacity, chewiness, △E, rehydration ratio, and average drying rate as responses. The combined drying conditions were optimized considering three independent variables at three different levels by response surface methodology. The results showed that the processing parameters of purple cabbage with combined microwave and hot air drying technology were microwave density at 2.5 W/g, moisture content of conversion point at 4.0 g/g, and hot air temperature at 55°C. Under these conditions, the anthocyanin content, DPPH antioxidant capacity, chewiness, △E, rehydration ratio, average drying rate, and overall score of the dried purple cabbage were 175.87 mg/100 g, 87.59%, 4,521.468 g, 26.5, 4.3, 0.76 g/min, and 0.785, respectively. Therefore, combined microwave and hot air drying technology is an effective, suitable method for drying purple cabbage., In this paper, we study the effects of microwave density, hot air temperature, and moisture content at conversion point on the quality of purple cabbage. We also optimize the parameters of combined microwave and hot air drying by response surface methodology (RSM).

Anthocyanin is a characteristic nutrient of purple cabbage, and phenylalanine ammonia-lyase (PAL) is the rate-limiting enzyme for the synthesis of anthocyanin by the phenylpropane pathway, which is an important part of plant secondary metabolism. In this research, 7 BrPAL, 8 BoPAL, and 15 BnPAL genes from genomes of Brassica rapa, Brassica oleracea, and Brassica napus, divided into four subgroups, evolved from 4 PAL genes in Arabidopsis. The amplification and evolution of the BrPAL gene are due to segmental duplication and purifying selection. BrPAL genes clustered in the same clade have similar intron/exon structures and motifs. The cis-regulatory elements are divided into four categories: light, growth and development, stress and hormones. The qRT-PCR assays showed that most BrPAL genes were upregulated by UVA, low temperature and MeJA and downregulated by FR, high temperature, salt, PEG, IAA, ABA and GA, and there was a positive correlation between anthocyanin content and gene expression. This study can be used as a source for the function of the cabbage PAL gene and its molecular mechanism of regulating anthocyanin synthesis and provides a theoretical basis for the molecular breeding of cabbage.

This work aimed to investigate the effect of five drying methods, namely hot-air drying (HD), microwave drying (MD), vacuum drying (VD), vacuum microwave drying (VMD), and vacuum freeze-drying (VFD), on the bioactive compounds, antioxidant activity, color, sensory attributes, and microstructure of purple cabbage. Different drying methods considerably affected the quality factors of the products. The highest remaining total phenolic content (TPC), total flavonoid content (TFC), and total anthocyanin content (TAC) concentrations were observed in the VFD cabbage at 10.57 mg GAE/g, 7.01 mg RE/g, 6.54 C-3-G mg eqiv/g, respectively. This was followed by the VMD samples at a TPC at 9.06 GAE mg/g, TFC level of 5.84 mg RE/g, and TAC at 3.80 C 3 – G mg eqiv/g. Furthermore, the VFD samples displayed the best performance in antioxidant activity. The antioxidant activity of the VMD samples was lower than the VD and MD samples, but higher than the HD samples. In terms of color and flavor, the VMD samples displayed a low ∆E (P

Antioxidants are compounds that are needed by the body to protect the body from free radical attacks that can trigger the emergence of degenerative diseases. One of the compounds that has free radical scavenger activity by inhibiting Reactive Oxygen Species (ROS) is flavonoids found in purple cabbage and white cabbage. This study aims to determine the total levels of flavonoids expressed as quercetin equivalent (EK) and antioxidant activity using the DPPH method (1,1-diphenyl-2- picrylhydrazyl). Identification of flavonoid compounds by Willstater test and determination of total flavonoid levels using spectrophotometry, AlCl3 reagent. Flavonoid levels were calculated using linear regression equations. Qualitative test for the presence of antioxidant activity using TLC and antioxidant activity test using the DPPH method with the parameter value of ES50. The qualitative test results showed that the ethanol extract of purple cabbage and white cabbage contained flavonoids. The total flavonoid content of ethanol extract of purple cabbage was 5.17% w/w (EK) and ethanol extract of white cabbage was 3.84% w/w (EK). Qualitative test with TLC showed antioxidant activity. The standard antioxidant activity values ​​of quercetin, ethanol extract of purple cabbage and white cabbage were 2.138±0.064 µg/mL; 154.445±0,999 µg/mL and 373.546±1.336 µg/mL. The antioxidant activity of purple cabbage is weak and white cabbage is very weak.

Background Water-soluble anthocyanin pigments are important ingredients in health-improving supplements and valuable for the food industry. Although great attention has been paid to the breeding and production of crops containing high levels of anthocyanin, genetic variation in red or purple cabbages (Brassica oleracea var. capitata F. rubra) has not yet been characterized at the molecular level. In this study, we identified the mechanism responsible for the establishment of purple color in cabbages. Results BoMYBL2–1 is one of the regulatory genes in the anthocyanin biosynthesis pathway in cabbages. It is a repressor whose expression is inversely correlated to anthocyanin synthesis and is not detectable in purple cabbages. Sequence analysis of purple cabbages revealed that most lacked BoMYBL2–1 coding sequences, although a few had a substitution in the region of the promoter 347 bp upstream of the gene that was associated with an absence of BoMYBL2–1 expression. Lack of transcriptional activity of the substitution-containing promoter was confirmed using transgenic Arabidopsis plants transformed with promoter::GUS fusion constructs. The finding that the defect in BoMYBL2–1 expression was solely responsible for purple coloration in cabbages was further demonstrated using genomic PCR and RT-PCR analyses of many other structural and regulatory genes in anthocyanin biosynthesis. Molecular markers for purple cabbages were developed and validated using 69 cabbage lines. Conclusion Expression of BoMYBL2–1 was inversely correlated to anthocyanin content, and purple color in cabbages resulted from a loss of BoMYBL2–1 expression, caused by either the promoter substitution or deletion of the gene. This is the first report of molecular markers that distinguish purple cabbages. Such markers will be useful for the production of intraspecific and interspecific hybrids for functional foods, and for industrial purposes requiring high anthocyanin content. Electronic supplementary material The online version of this article (10.1186/s12870-018-1290-9) contains supplementary material, which is available to authorized users.

Tofu is a food that is in great demand by people in Indonesia. In processing tofu, producers usually use formalin as a preservative to maintain storage time. The use of formalin in food can cause poisoning. This study aims to determine the method that can be used to unlock the potential of purple cabbage plants (Brasicca oleracea L) as an alternative natural indicator in the qualitative examination of formalin and to obtain experimental results using purple cabbage extract (Brasicca oleracea L) as an alternative natural indicator of deep formalin examination know. Purple cabbage (Brassica oleracea L) is a kind of typical vegetable plant. The typical color is caused by the presence of anthocyanin. This anthocyanin can be used as an alternative natural indicator. Qualitative formalin examination using purple cabbage extract and formalin test kit. The tofu samples used were tofu samples containing 0%, 1%, 0.5%, 0.25%, 0.12%, 0.06% and 0.03% formalin. The solvent used for purple cabbage extract is distilled water. The parameters observed were color changes. The results showed that purple cabbage extract can be used as an alternative natural indicator on formalin examination in tofu. Tofu that does not contain formaldehyde undergoes a change in color from purple to pink after dropping purple cabbage extract, while tofu containing formalin does not change color after dropping purple cabbage extract.

Light is essential for plant growth. Light intensity, photoperiod and light quality all affect plant morphology and physiology. Compared to light intensity, photoperiod, little is known about the effects of different monochromatic lights on crop species. To investigate how different lighting conditions influence crops with heterogeneous colors in leaves, we examined photosynthetic characteristics and quality (regarding edibility and nutrition) of purple cabbage under different combinations of lights. Eight different treatments were applied including monochromic red (R), monochromic blue (B), monochromic yellow (Y), monochromic green (G) and the combination of red and blue (3/1, RB)， red/blue/yellow (3/1/1, RBY)， red /blue/green (3/1/1,RBG) and white light as the control. Our results indicate that RBY (3/1/1) treatment promotes the PSII activity of purple cabbage, resulting in improved light energy utilization. By contrast, both G and Y lights alone have inhibitory effect on the PSII activity of purple cabbage. In addition, RBY (3/1/1) significantly boosts the anthocyanin and flavonoids content compared with other treatments. Although we detected highest soluble protein and vitamin C content under B treatment (increased by 29.99% and 14.29% compared with the control respectively), RBY (3/1/1) appeared to be the second-best lighting condition (with soluble protein and vitamin C content increased by 8.63% and 4.07% respectively compared with the control). Thus we prove that the addition of yellow light to the traditional combination of red/blue lighting conditions is beneficial to synthesizing photosynthetic pigments and enables superior outcome of purple cabbage growth. Our results indicate that the growth and nutritional quality of purple cabbage are greatly enhanced under RBY (3/1/1) light, and suggest that strategical management of lighting conditions holds promise in maximizing the economic efficiency of plant production and food quality of vegetables grown in controlled environments.

Natural dyes extracted from purple cabbage, coffee, blueberry and turmeric were used as sensitizers to fabricate dye sensitized solar cells (DSSC). The dyes were extracted by using an ultrasonic extraction method by setting parameter of 30 o C at 30 minutes and 37 Hz. UV-Vis spectrophotometer is used to measure the absorbance of cocktail dyes which consist of purple cabbage and blueberry, turmeric and coffee that were extracted using ethanol and distilled water. From the result, the broadest spectrum between the extracted dyes is the cocktail dye from purple cabbage and blueberry which is in the range of 550 nm and having the lowest photon energy of 1.85 eV compare to the later. The result shows that, the combination of purple cabbage and blueberries as cocktail dye have good potential in future development of DSSC.