Hypertension is one of the major causes of cardiovascular-related diseases, which is highly associated with angiotensin-I-converting enzyme (ACE) activity and oxidative stress. In this study, winged bean seed (WBS), a potential source of protein, was utilised for the production of bifunctional proteolysate and biopeptides with ACE inhibitory and antioxidative properties. An enzymatic approach was applied, coupled with pretreatment of shaking and centrifuging techniques to remove endogenous ACE inhibitors prior to proteolysis. ACE inhibition reached its highest activity, 78.5%, after 12 h proteolysis while antioxidative activities, determined using assays involving DPPH˙ radical scavenging activity and metal ion-chelating activity, reached peaks of 65.0% and 65.7% at 8 h and 14 h, respectively. The said bioactivities were proposed to share some common structural requirements among peptides. A two-dimensional approach was employed for characterisation of effective peptides based on hydrophobicity, using RP-HPLC, and isoelectric property, using isoelectric focusing technique. Results revealed that acidic and basic peptides with partially higher hydrophobicity provided higher ACE inhibition activity than did neutral peptides. Finally, by using Q-TOF mass spectrometry, two peptide sequences (YPNQKV and FDIRA) with ACE inhibitory and antioxidative activities were successfully matched with a database. This study indicates that the WBS proteolysate can be a potential bifunctional food ingredient as the identified biopeptides demonstrated both ACE inhibitory and antioxidative activities in vitro.

Current work evaluated the effects of 12-month storage, at chilled (4ºC) and ambient (25ºC) temperatures, on the physical properties, resistant starch (RS) content and antioxidant profile of purple sweet potato (PSP) powder. This study revealed two findings: (i) The antioxidant content of food powders was not always reflective of its antioxidant capacity and (ii) Chilled storage could not prevent the loss of RS and antioxidant activity upon 12-month storage. It is suggested that measurements of antioxidant content and antioxidant activity should be performed concurrently on the same sample.

Purple sweet potato (PSP) is sensorially attractive and rich in a valuable source called “anthocyanins,” but this tuberous crop is highly perishable. It is largely found in hot and humid countries, such as the South East Asia region. This study applied the drum drying technique to turn PSP into a shelf‐stable powder product, wherein an issue related to severe discolouration (browning) was identified. Hence, two moist‐heat pretreatments, namely boiling and steaming, were performed prior to drum drying. The effects of pretreatment on color changes, physicochemical, antioxidant, and resistant starch properties in the final product were analyzed. Both pretreatments had successfully retained the purplish color in the final product, in which steaming displayed better effects when compared with boiling in powder yield (243.02 g/100 g vs. 180.87 g/100 g), total anthocyanin content (121.71 mg/100 g vs. 83.72 mg/100 g), and resistant starch content (3.06 g/100 g vs. 2.53 g/100 g). The study outcomes demonstrated the capability of steaming in producing PSP powder that retained the original color and the health‐promoting compounds (i.e., anthocyanins and resistant starch), which appeared to be better than boiling, thus pretreatment on PSP prior to drum drying is highly recommended. Practical applications This study successfully tackles the browning issue identified in purple sweet potato processing, via two simple and straightforward heating methods; boiling and steaming. The tuber is turned into a shelf‐stable, ready‐to‐use powder that acts as a thickener in soups, bakeries and fabricated snacks. The final powder product displays an attractive purplish color, exceptional functionality (in terms of water absorption capacity) and is loaded with health‐promoting compounds including antioxidant and resistant starch. These findings proved that moist‐heat treatments retain the purplish color, anthocyanins and resistant starch content in drum‐dried purple sweet potato powder well and provide additional health benefits besides acting as an ordinary food thickener.

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