Composition and Biological Properties of Blanched Skin and Blanch Water Belonging to Three Sicilian Almond Cultivars

Abstract

The almond industry produces, by bleaching and stripping, two by-products: blanched skin (BS) and blanch water (BW). The aim of this study was to investigate the nutritional and polyphenolic profile, as well as the antioxidant, antimicrobial, antiviral, and potential prebiotic effects of BS and BW from three different Sicilian cultivars. The total phenols and flavonoids contents were ≥1.72 and ≥0.56 g gallic acid equivalents and ≥0.52 and ≥0.18 g rutin equivalents/100 g dry extract (DE) in BS and BW, respectively. The antioxidant activity, evaluated by 2,2-diphenyl-1-picrylhydrazyl scavenging ability, trolox equivalent antioxidant capacity, ferric-reducing antioxidant power, and oxygen radical absorbance capacity, was ≥3.07 and ≥0.83 g trolox equivalent/100 g DE in BS and BW, respectively. Isorhamnetin-3-O-glucoside was the most abundant flavonoid detected in both by-products. No antimicrobial effect was recorded, whereas BS samples exerted antiviral activity against herpes simplex virus 1 (EC₅₀ 160.96 μg/mL). BS also showed high fibre (≥52.67%) and protein (≥10.99) contents and low fat (≤15.35%) and sugars (≤5.55%), making it nutritionally interesting. The present study proved that the cultivar is not a discriminating factor in determining the chemical and biological properties of BS and BW.

Keywords: almond by-products; antimicrobial activity; antioxidant properties; antiviral activity; cultivar; nutritional profile; polyphenols; prebiotic effect.

Figure 1

Agglomerative two-way hierarchical clustering analyses of the nutritional profiles of blanched skin (BS) samples belonging to the different producers of Fascionello (F), Pizzuta (P), and Tuono (T) cultivars.

Figure 2

Agglomerative two-way hierarchical clustering analyses of the fatty acid profiles of blanched skin (BS) belonging to Fascionello, Pizzuta, and Tuono cultivars.

Figure 3

Agglomerative two-way hierarchical clustering analyses of the polyphenolic profiles of blanched skin extracts (BSE) belonging to Fascionello, Pizzuta, and Tuono cultivars.

Figure 4

Agglomerative two-way hierarchical clustering analyses of the polyphenolic profiles of blanch water extracts (BWE) belonging to Fascionello, Pizzuta, and Tuono cultivars.

Figure 5

Percentage distribution (%) of the various classes of polyphenols identified in the three different cultivars investigated (Fascionello, Pizzuta, and Tuono) in blanched skin extracts (BSE, panel (A)) and blanch water extracts (BWE, panel (B)). ^a p < 0.05 vs. Pizzuta cultivar; ^b p < 0.05 vs. Tuono cultivar.

Figure 6

Viability assay of Vero cells treated with BSE from Fascionello and Tuono cultivars. Vero cells were treated with different concentrations of BSE (50 μg/mL, 100 μg/mL, 150 μg/mL, 200 μg/mL, and 300 μg/mL). The cells were collected 72 h post-treatment. The cell viability was carried out as described in the Materials and Methods section and graphically reported as a percentage of viability (%). The assay was performed as means of triplicates ± SD. I to VI represent different producers.

Figure 7

Effect of BSE on HSV-1 replication by plaque reduction assay. Vero cells were infected with HSV-1 dilutions for 1 h and then treated with BSE from Fascionello and Tuono cultivars (200 μg/mL, 150 μg/mL, and 100 μg/mL). DMSO was included as a control. Data are expressed as mean (± SD) of triplicates. # indicates the micro-plaques. * p < 0.05, *** p < 0.001, **** p< 0.0001 vs. HSV-1 + DMSO. I to VI represent different producers.