Different food processing strategies could disrupt the cellular barriers of plant tissues, thus promoting the bioaccessibility (release) of plant bioactives during digestion(1]. However, there is a lack of understanding of oral and gastrointestinal bioaccessibility of blueberry anthocyanins, and the impact of different food processing strategies on anthocyanin release.
The aims of this study were to determine: (Reference Sensoy1) the extent of anthocyanin bioaccessibility in blueberries following mastication and gastrointestinal digestion; and (Reference Brodkorb, Egger and Marie Alminger2) the impact of different processing strategies on anthocyanin bioaccessibility.
Bioaccessibility of blueberry anthocyanins was evaluated in three commonly consumed forms: fresh, frozen-thawed and a smoothie. In vivo mastication of both fresh and frozen-thawed blueberries, performed by 3 healthy participants (Ethics Committee Reference: HR/DP-20/21-23191), was compared to the in vitro simulated oral phase of the INFOGEST protocol(Reference Brodkorb, Egger and Marie Alminger2). Fresh human chewed (FHC), fresh simulated chewed (FSC), frozen-thawed human chewed (FTHC), frozen-thawed simulated chewed (FTSC) and blueberry smoothie (BS) samples were further digested using the INFOGEST gastric and duodenal phases. Anthocyanin contents in samples were determined by UPLC-MS/MS, presented as mg per g of fresh weight (fw). Anthocyanin bioaccessibility was calculated as the free anthocyanin content as a percentage (%) of the total content of blueberries. Overall, 55 types of anthocyanins were found in blueberry samples. Oral bioaccessibility accounted for <10% of the total anthocyanin released in all samples. Anthocyanin release in simulated mastication (5.96 ± 0.48% for FSC and 7.97 ± 0.19% for FTSC) was significantly higher than in vivo mastication (1.95 ± 0.17% for FHC and 5.03 ± 0.09% for FTHC, p < 0.05). Frozen-thawed samples had significantly higher anthocyanin oral bioaccessibility than fresh samples (p < 0.05). Compared with mastication, blending for making a smoothie released 8.44 ± 0.31% anthocyanins in the BS sample with a content of 0.196 ± 0.007 mg/g fw, significantly higher than the other samples (p < 0.05). Anthocyanin bioaccessibility following gastric digestion was higher than the oral phase for all samples (p < 0.05), with BS showing 54.79 ± 1.10% release (1.273 ± 0.026 mg/g fw), followed by FTSC (52.41 ± 2.20%), FTHC (37.45 ± 0.73%), FSC (28.71 ± 0.60%) and FHC (19.63 ± 0.43%). After duodenal digestion, anthocyanin recoveries were reduced for all samples (4.67 ± 0.01% for FHC; 6.19 ± 0.13% for FSC; 4.98 ± 0.14% for FTHC; 5.63 ± 0.04% for FTSC; and 9.05 ± 0.13% for BS). This reduction is likely due to the higher pH environment in the duodenal phase relative to the gastric environment. In conclusion, blueberries consumed as a smoothie had significantly higher anthocyanin bioaccessibility than frozen-thawed samples, which were higher than fresh blueberries. This difference between samples is consistent with likely changes in the food matrix structure following blending and freezing. Importantly, simulated mastication leads to higher release of anthocyanins than in vivo mastication, so results from in vitro mastication should be interpreted with caution.
Acknowledgments
The research is supported by the joint PhD scholarship programme of King's College London and China Scholarship Council (K-CSC) to Zicheng Zhang.
