|Carrots and blueberries - superfoods you cannot ruin by grinding, blending and even the falsely depreciated use of the microwave oven.|
I've discussed some of these studies in the SuppVersity Facebook News (subscribe by liking if you haven't done so), before. Zaiter, et al., for example, found that the particle size of your green tea powder will affect its antioxidant activity - with the best grinding conditions and particle size being rather rough, i.e. 6000 rpm and 100–180 μm (Zaiter 2016). Likewise, I've addressed the issue of microwaving both in the Facebook News and here on suppversity.com. What I haven't discussed in detail, though, is "whether and how different home-based food preparation methods, including blending, chopping with/without microwaving, might release different levels of beneficial bioactives from carrot and blueberry food models" (Gao 2017) - simply because the study at hand is the first to do that.
|The scientists didn't just assess the content of vitamins and phenols, but also tested the free radical scavenging and absorbing capacity, as well as the biological, anti-inflammatory effects of the processed blueberries and carrots.|
"Carrots were cut into one-inch length, accurately weighted and blended with pure water (1:2, w/v) for 20 s using the highest speed in a blender. The blended samples were separated into two parts, one part was microwaved for 10 s to inactivate the enzymes in the carrots or blueberries, while another part was not microwaved to examine whether and how their inherent enzymes might alter the releasable level of bioactive components. The blended carrot samples were centrifuged at 10,000 g for 5 min, and the supernatant was collected and the calculated volume of acetone was added to make a final concentration of 50% acetone (v/v) for further assays. Blueberries were extracted following the same procedure without cutting. The extracts were kept at 4°C until testing" (Gao 2017).
Afterward, the samples were analyzed for their free radical scavenging ability using DPPH, ORAC, hydroxyl radical (HOSC) and - most importantly - macrophage cell assays (the latter mirror the biological effects of the extracts much better than the aforementioned chemical assays) - and here's what they found:
- The β-carotene availability in carrots concentration extracted from the chopped carrot was below the limit of detection (LOD). All tested commercial blenders were able to enhance the release of β-carotene at a level of 0.2–0.94 μg/g fresh carrot, which was significantly greater than the chopped counterpart.
In addition, no difference in extractable β-carotene was observed between the ground carrots using the same blender with and without microwaving.
- The anthocyanin content of the blueberry samples was not affected by any of the preparation methods. If you scrutinize the data in Figure 2 you will see that the differences in anthocyanin content for all samples were well within the statistical margin or error for the HPLC analysis for all commercial blenders/grinders.
Microwaving, on the other hand, did change the content of these powerful antioxidants [(a) malvidin-3-O-glucoside and (b) cyanidin- 3-O-glucoside were measured representative for the total anthocyanin content] - and significantly that is. The scientists argue that this difference may be explained by a decrease in the activity of inherent enzymes such as glucosidases and other carbohydrases. Unfortunately, these enzymes have previously been shown to increase the bioactive availability from fruits and other botanicals including vegetables (Otieno 2007; Alrahmany 2012).
- The total phenolic content (TPC) of carrots ranged from 0.19 to 0.34 mg gallic acid equivalents per gram of fresh carrot, which was equivalent to 593.6–1062.2 mg chlorogenic acid per kilogram of fresh carrot.
It's not just about food processing, it's also about food combining: Whole Eggs Can Boost Your Beta-Carotene and Vitamin E Uptake from Veggie Salad W/ Oil Dressing by 400%-700% | more
In contrast to carrots, however, the availability of total phenolic contents in the blueberries did, however, increase significantly with microwaving, "indicating that inactivation of blueberry enzymes might reduce the loss of phenolics during grinding and storage of the blended blueberries" (Gao 2017), so that the TPC results clearly indicate that "microwaving immediately after blending may be recommended for blended blueberry to retain a desirable availability of total phenolics" (Gao 2017).
Foods in the Limelight: Blueberry Smoothies, Egg Protein & 'Healthy Eating' | Plus: How to Diagnose Gluten Sensitivity? Find out in this SV Classic!
For blueberries, all three assays, i.e. the DPPH assay (TROLOX), the ORAC assay and the HOSC assay produced more or less random effects - a clear trend for increased or decreased values with either blending, grinding or microwaving was not observed.
- The biological anti-inflammatory activity that was measured in macrophages that were exposed to an LPS challenge, no differences were observed for both, the carrot and blueberry samples prepared using different commercial blenders/grinders in releasable levels of potential anti-inflammatory components in the LPS-induced IL-6 mRNA expression in macrophage cells (Figure 7). The inhibitory effects of blueberry extracts on LPS-induced COX-2 and TNF-α mRNA expressions could be dose-dependent.
- Alrahmany, Roaaya, and Apollinaire Tsopmo. "Role of carbohydrases on the release of reducing sugar, total phenolics and on antioxidant properties of oat bran." Food chemistry 132.1 (2012): 413-418.
- Gao, Boyan, et al. "Home‐based preparation approaches altered the availability of health beneficial components from carrot and blueberry." Food Science & Nutrition (2017).
- Gustafson, Sally J., et al. "Effect of postharvest handling practices on phytochemical concentrations and bioactive potential in wild blueberry fruit." Journal of Berry Research 2.4 (2012): 215-227.
- Otieno, D. O., J. F. Ashton, and N. P. Shah. "Isoflavone phytoestrogen degradation in fermented soymilk with selected β-glucosidase producing L. acidophilus strains during storage at different temperatures." International journal of food microbiology 115.1 (2007): 79-88.
- Zaiter, Ali, et al. "Effect of particle size on antioxidant activity and catechin content of green tea powders." Journal of food science and technology 53.4 (2016): 2025-2032.