Physico‐functional and antioxidant properties of purple‐flesh sweet potato flours as affected by extrusion and drum‐drying treatments

Effects of extrusion and drum‐drying treatments on physico‐functional and antioxidant properties of flours prepared from purple‐flesh sweet potato were evaluated. Extrusion variables were feed moisture contents (MC; 10%, 13%, 16%) and screw speeds (SS; 250, 325, 400 r.p.m.), whereas drum‐drying was done at 120, 130 or 140 °C. Effects of MC were generally greater than SS on flour properties. Extruded flours showed higher water absorption and water solubility indices compared with control nonextruded flours. Regardless of SS, total phenolic content and antioxidant activities (DPPH and ABTS) of flours processed at 10% MC were significantly higher than those at 13% and 16%. Both extruded and drum‐dried flours exhibited no peak viscosity, indicating complete gelatinisation of starch. Maximum phenolic content and antioxidant activities of drum‐dried flours were obtained at 140 °C. Although drum‐dried flours had higher antioxidant capacity than extruded flours, both flours could potentially be used as food ingredients.     

Physicochemical properties of rice flour as affected by alkaline soaking and washing treatments

Effects of alkaline [NaOH, saturated Ca(OH)₂ and/or limewater] soaking and subsequent washing (with water vs. without washing) treatments on physicochemical properties of rice flour were investigated. Alkaline soaking treatment generally caused a loss of granule angularity but some birefringence was observed for unwashed alkali-soaked flour granules. After soaking, protein content of the flours significantly (P < 0.05) decreased but swelling power significantly (P < 0.05) increased compared to the control (soaked in water). The washed flours had lower protein content than unwashed flours (3.77–6.87% vs. 5.26–7.87%). The NaOH-soaking treatment yielded higher swelling power and solubility, respectively, for unwashed and washed flours. Alkaline soaking increased breakdown but decreased pasting temperature, trough viscosity, final viscosity and setback of the paste compared to the control. Compared to the control, hardness of soaked flour paste was lower due to lower final viscosity and setback. Overall, physicochemical properties of rice flour could be modified by alkali-soaking and washing treatments.     

Effects of cricket powder on selected physical properties and US consumer perceptions of whole-wheat snack crackers

Successful introduction of insect consumption to a reluctant US population requires novel insect-based foods that are responsive to consumers’ expectations of sensory quality. Based on our ‘product appropriateness’ data, snack crackers were formulated with increasing levels of cricket powder (0%, 5%, 10%, 15%, and 20%) in substitution of whole-wheat flour. Colour, texture, flavour and overall perceptions of snack crackers were evaluated by 150 US consumers in terms of preference (2-alternative choice), degree of liking (9-point scale) and acceptability (yes/no). Flavour liking was most highly correlated with overall liking (r = 0.93). Instrumental analyses indicated that increasing cricket powder resulted in darker and harder crackers, negatively impacting colour and texture preference at 5% and 15% cricket powder addition, respectively. Snack crackers remained acceptable at 15% wheat flour substitution (80% acceptability; mean overall liking = 5.5). However, to promote future consumption, an upper limit of 7.9% cricket powder addition is recommended until sensory quality can be improved.     

Novel peptides from dried squid head by-products obtained from snack process

The novel peptides were successfully produced with commercial protease hydrolysis (Alcalase® and Flavourzyme®) at the fixed concentration of 3%by weight of protein in substrate. The hydrolysis was performed at various hydrolysis times (0, 300, 450, 600 and 750 min) at the optimal pH and temperature. When the hydrolysis was performed until 750 min, the peptide solutions with high soluble protein content were resulted (47.58 and 42.53 mg protein per mL for Alcalase® and Flavourzyme® hydrolysis, respectively). After freeze drying, the peptide powder from Alcalase® and Flavourzyme® hydrolysis had degree of hydrolysis at 71.87% and 66.39%, respectively. Alcalase® hydrolysis provided the novel peptide fraction with DPPH scavenging, ABTS activity and ACE-inhibitory activity at 64.20%, 102.50 µg mL⁻¹ and 56.98%, respectively. This peptide fraction possessed the lowest molecular weight (m/z 807.418) as detected by MALDI-TOF/MS, and the most potent peptide sequence was Arg-Glu-Gly-Tyr-Phe-Lys which has the potential as functional ingredient in novel food, snacks and beverages.     

Concentrating sulphur-containing flavour from Toona sinensis shoots using corn oil with and without aqueous dispersion

Toona sinensis (TS) shoot is a seasonal and quick deteriorating vegetable with unique alliaceous flavour. In this study, corn oil was used to concentrate the sulphur-containing compounds responsible for the unique TS flavour with and without aqueous dispersion. The level of sulphur-containing compounds in TS shoots was 0.32 μg g⁻¹ and concentrated to 2.34 μg g⁻¹ in the corn oil with aqueous dispersion. The sulphur-containing compounds, trans-2-Mercapto-3,4-dimethyl-2,3-dihydrothiophene and (E,Z)-Di-1-propenyldisulphide, were identified in the corn oil, while they were not detected in the oil without aqueous dispersion. Based on sensory and electronic nose analysis, the aroma of corn oil with aqueous medium extraction had stronger alliaceous aroma than TS shoots and the extraction corn oil without aqueous dispersion. With aqueous dispersion assistance, the sulphur-containing aroma compounds in TS shoots were effectively concentrated in corn oil. The flavour-enriched oil could serve as a flavour ingredient to deliver TS shoots aroma for different food applications.     

Low-sodium roasted peanuts: effects of salt mixtures (NaCl,KCl and glycine) on consumer perception and purchase intent

The effects of ten treatment combinations of two salts (NaCl, KCl) and glycine were evaluated on low-sodium roasted peanuts. Consumers’ (N = 330, recruited from college campus) liking, emotions, perceived saltiness and bitterness intensity, satisfaction and purchase intent (PI) of peanuts were measured following a balanced incomplete block design (t = 10, k = 3, r = 9, b = 30, λ = 2, e₂ = 0.74). Emotions and PI were evaluated both before and after presenting a low-sodium health benefit message. Sodium content of peanuts was reduced from 140 mg Na/50 g peanuts to 41.67 mg Na/50 g without significantly affecting liking scores and with positive PI over 60%. In general, high bitterness and low saltiness intensity ratings negatively affected liking and satisfaction. Consumers expressed less satisfaction when perceived saltiness intensity was ‘Not Enough’ than when ‘Too Much.’ Based on optimisation analysis, any formulation within the range of 59-100/0-40/0-12.5% NaCl/KCl/Gly- representing a potential 37% sodium reduction past minimum ‘low sodium’ requirements- will yield an acceptable product.     

An improved determination method for tyramine in foods using ultra-high performance liquid chromatography with benzylamine as internal standard

Tyramine has been considered a biological hazard for foods and beverages. In this study, an ultra-high pressure liquid chromatography (UPLC) with benzylamine as an internal standard in dansyl chloride pre-column derivatisation was developed to determine tyramine in various foods. Different from other tyramine determination methods usually without an internal standard in the pre-column derivatisation, benzylamine which chemical structure is similar to tyramine was selected as an internal standard. The limits of detection and quantification of this method were 0.05 and 0.25 mg L⁻¹, respectively, while the relative standard deviations of repeatability and reproducibility were 2.1% and 3.1%, respectively. The sensitivity and reliability of this method were also evaluated by determining tyramine in common liquid, pasty and solid foods. The recoveries of tyramine in these foods were between 87.3% and 96.8% by using this method. Overall, it is a fast, inexpensive, reliable and sensitive method to measure tyramine in different food products.     

Antimicrobia activity of garlic (Allium sativum L.) and holy basil (Ocimum sanctum L.) essential oils applied by liquid vs. vapour phases

Antimicrobial activity of garlic (Allium sativum L.) and holy basil (Ocimum sanctum L.) essential oils (GEO and HBEO, respectively) was evaluated in liquid vs. vapour phases. Diallyl disulphide and diallyl trisulphide in GEO while eugenol, caryophyllene and methyl eugenol in HBEO were predominant active compounds. Individually, GEO was highly effective in the vapour phase, showing the greatest antimicrobial activity (P ≤ 0.05) against Bacillus cereus and Staphylococcus aureus with complete inhibition, followed by Salmonella typhimurium and Pseudomonas fluorescens, but had no effect on Escherichia coli, Lactobacillus plantarum or Listeria monocytogenes. The combined GEO:HBEO (a 1:1 ratio) at 30 μL demonstrated inhibitive activity against all bacteria tested with complete inhibition against B. cereus and S. aureus. Minimum bactericidal concentration (MBC) of the combined oil was <0.4% v/v, except for P. fluorescens requiring a higher MBC (1.5%, v/v). This study demonstrated potential of the combined GEO:HBEO to be used for food preservation applications.