Effects of different drying methods on the bioactive compounds and antioxidant properties of edible Centaurea (<i>Centaurea cyanus</i>) petals

Fernandes, Luana; Casal, Susana; Pereira, José Alberto; Saraiva, Jorge Alexandre; Ramalhosa, Elsa

doi:10.1590/1981-6723.21117

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Brazilian Journal of Food Technology

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Original Article • Braz. J. Food Technol. 21 • 2018 • https://doi.org/10.1590/1981-6723.21117 copy

Effects of different drying methods on the bioactive compounds and antioxidant properties of edible Centaurea (Centaurea cyanus) petals

Efeito de diferentes métodos de secagem nos compostos bioactivos e propriedades antioxidantes de pétalas de Centáurea (Centaurea cyanus )

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The present study aimed to evaluate the effects of hot-air convective drying, shade drying and freeze-drying on the bioactive compounds and antioxidant activity of Centaurea ( Centaurea cyanus L.) petals, as well as on several of their physicochemical properties. All the dried samples showed different appearances as compared to fresh petals, with lower titratable acidity, lower carotenoids and hydrolysable tannins contents, and greater antioxidant activity. Of the drying methods, shade drying presented the highest values for monomeric anthocyanins, flavonoids, hydrolysable tannins, total reducing capacity and antioxidant activity. By contrast, greater losses were observed as a result of hot-air convective drying. Thus shade drying is a highly promising process that should be considered as a suitable drying method for Centaurea petals.

Keywords:
Centaurea petals; Hot-air convective drying; Shade drying; Freeze-drying; Bioactive compounds; Antioxidant activity

Samples	Time (h)	a_W	Weight Loss (%)	Titratable Acidity (g citric acid/100 g DW)
Fresh	--	0.97 ± 0.01^d	----	0.69 ± 0.05^c
Hot-air convective dried	1	0.92 ± 0.01^d	29.8 ± 1.1^a	0.24 ± 0.05^a
	2	0.90 ± 0.01^d	59.3 ± 1.5^b	0.47 ± 0.03^b
	3	0.67 ± 0.05^c	72.5 ± 2.3^c	0.53 ± 0.03^b,c
	4	0.47 ± 0.01^b	73.0 ± 3.7^c	0.66 ± 0.04^c
Shade-dried	72	0.47 ± 0.01^b	77.8 ± 6.3^c	0.43 ± 0.03^b
Freeze-dried	24	0.33 ± 0.01^a	88.0 ± 0.3^d	0.49 ± 0.05^b

Samples	Time (h)	Monomeric anthocyanins (mg Cy 3-glu/g DW)	Flavonoids (mg QE/g DW)	Hydrolysable tannins (mg TAE/g DW)	Total Reducing Capacity (TRC) (mg GAE/g DW)	Total carotenoids (µg β-carotene/g DW)	DPPH EC₅₀ (mg extract/ml)	Reducing power EC₅₀ (mg extract/ml)
Fresh	--	3.95 ± 0.17^e	21.87 ± 0.64^e	13.67 ± 0.27^c	6.27 ± 0.17ª^,b	28.1 ± 2.5^c	0.92 ± 0.07^c	3.65 ± 0.08^d
Hot-air	1	2.15 ± 0.05^b	10.04 ± 0.42^a	5.44 ± 0.94ª^,b	6.12 ± 1.13^a	5.7 ± 0.2^b	0.83 ± 0.03^c	1.68 ± 0.02^c
	2	3.21 ± 0.02^d	17.71 ± 1.68^d	6.20 ± 0.76^b	9.84 ± 1.00^c	7.9 ± 1.2^b	0.72 ± 0.03^b	1.41 ± 0.03^b
	3	1.90 ± 0.05^a	11.32 ± 0.62ª^,b	3.56 ± 0.36^a	7.34 ± 1.02ª^,b	6.0 ± 0.8^b	0.69 ± 0.03^b	1.63 ± 0.21^c
	4	2.60 ± 0.07^c	12.96 ± 1.43^b,c	4.78 ± 0.58ª^,b	7.93 ± 1.02ª^,b,c	8.1 ± 1.2^b	0.89 ± 0.10^c	1.79 ± 0.06^c
Shade-dried	72	5.11 ± 0.04^f	30.06 ± 2.11^f	6.77 ± 2.01^b	15.12 ± 2.35^d	2.2 ± 0.5^a	0.55 ± 0.02^a	1.10 ± 0.03ª
Freeze-dried	24	2.23 ± 0.05^b	13.95 ± 0.68^c	6.05 ± 1.94^b	8.43 ± 1.09^b,c	0.2 ± 0.1ª	0.85 ± 0.05^c	1.78 ± 0.09^c

	Monomeric anthocyanins	Flavonoids	Hydrolysable tannins	EC₅₀ DPPH	EC₅₀ Reducing Power
Total reducing capacity	0.668^**	0.737^**	-0.065	- 0.751^**	-0.531^**
Monomeric anthocyanins	___	0.965^**	0.510^**	- 0.402^**	0.087
Flavonoids	___	___	0.491^**	- 0.502^**	0.042
Hydrolysable tannins	___	___	___	0.302	0.787^**
EC₅₀ DPPH	___	___	___	___	0.650^**

Instituto de Tecnologia de Alimentos - ITAL Av. Brasil, 2880, 13070-178 Campinas - SP / Brasil, Tel 55 19 3743-1762 - Campinas - SP - Brazil
E-mail: bjftsec@ital.sp.gov.br

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[1] * Elsa Ramalhosa, Instituto Politécnico de Bragança, Escola Superior Agrária, Centro de Investigação de Montanha (CIMO), Campus de Santa Apolónia, CEP: 5300-253, Bragança - Portugal, e-mail: elsa@ipb.pt