Assembly-line synthesis of organic molecules with tailored shapes.

Molecular 'assembly lines', in which organic molecules undergo iterative processes such as chain elongation and functional group manipulation, are found in many natural systems, including polyketide biosynthesis. Here we report the creation of such an assembly line using the iterative, reagent-controlled homologation of a boronic ester. This process relies on the reactivity of α-lithioethyl tri-isopropylbenzoate, which inserts into carbon-boron bonds with exceptionally high fidelity and stereocontrol; each chain-extension step generates a new boronic ester, which is immediately ready for further homologation. We used this method to generate organic molecules that contain ten contiguous, stereochemically defined methyl groups. Several stereoisomers were synthesized and shown to adopt different shapes-helical or linear-depending on the stereochemistry of the methyl groups. This work should facilitate the rational design of molecules with predictable shapes, which could have an impact in areas of molecular sciences in which bespoke molecules are required.

Whey protein mouth drying influenced by thermal denaturation.

Whey proteins are becoming an increasingly popular functional food ingredient. There are, however, sensory properties associated with whey protein beverages that may hinder the consumption of quantities sufficient to gain the desired nutritional benefits. One such property is mouth drying. The influence of protein structure on the mouthfeel properties of milk proteins has been previously reported. This paper investigates the effect of thermal denaturation of whey proteins on physicochemical properties (viscosity, particle size, zeta-potential, pH), and relates this to the observed sensory properties measured by qualitative descriptive analysis and sequential profiling. Mouthcoating, drying and chalky attributes built up over repeated consumption, with higher intensities for samples subjected to longer heating times (p < 0.05). Viscosity, pH, and zeta-potential were found to be similar for all samples, however particle size increased with longer heating times. As the pH of all samples was close to neutral, this implies that neither the precipitation of whey proteins at low pH, nor their acidity, as reported in previous literature, can be the drying mechanisms in this case. The increase in mouth drying with increased heating time suggests that protein denaturation is a contributing factor and a possible mucoadhesive mechanism is discussed.

Saturated fat replacement in short dough biscuits with HPMC and lecithin stabilised nanoemulsions.

Biscuits contain high proportions of saturated fats, which could lead to an adverse health effect. The objective of this study was to study the functionality of a complex nanoemulsion (CNE), stabilised with hydroxypropyl methylcellulose and lecithin, when used as a saturated fat replacer in short dough biscuits. Four biscuit formulations were studied including a control (butter) and three formulations where 33% of the butter was replaced with either extra virgin olive oil (EVOO), with CNE, or with the individual ingredients of the nanoemulsion added separately (INE). The biscuits were evaluated by texture analysis, microstructural characterisation, and quantitative descriptive analysis by a trained sensory panel. The results showed that incorporation of CNE and INE yielded doughs and biscuits with significantly higher (p < 0.05) hardness and fracture strength values than the control. The doughs made of CNE and INE showed significantly less oil migration during the storage than EVOO formulations, which was confirmed by the confocal images. The trained panel did not find significant differences in crumb density and hardness on the first bite among CNE, INE and the control. In conclusion, nanoemulsions stabilised with hydroxypropyl methylcellulose (HPMC) and lecithin can work as saturated fat replacers in short dough biscuits, providing satisfactory physical characteristics and sensory attributes.

Oral retention of thermally denatured whey protein: In vivo measurement and structural observations by CD and NMR.

This study investigated structural changes and the in vivo retention in the oral cavity of heated whey protein concentrate (WPC). Heated WPC was shown to have both a higher retention time in the oral cavity compared to unheated whey protein up to 1 min post swallow, and a concomitant increase in free thiol concentration. Nuclear magnetic resonance and circular dichroism demonstrated structural changes in the secondary and tertiary structures of the WPC upon heating. Structural loss of the ß-barrel was shown to increase during heating, leading to the exposure of hydrophobic regions. The increase in free thiols and hydrophobic regions are two factors which are known to increase mucoadhesive strength and hence increase oral retention of heated whey protein which may subsequently increase the perception of mouthdrying.

An Investigation of the Influence of Age and Saliva Flow on the Oral Retention of Whey Protein and Its Potential Effect on the Perception and Acceptance of Whey Protein Beverages.

Protein fortified products are regularly recommended to older adults to improve nutritional status and limit sarcopenia. However protein fortification can elicit negative sensory attributes such as mouthdrying. Sensitivity to mouthdrying can increase with age, yet the influence of saliva flow and mucoadhesion remain uncertain. Here, two studies tested different whey protein beverages (WPB); 22 healthy younger volunteers completed a pilot and 84 healthy volunteers from two age groups (18-30; 65+) completed the main study. In both studies salivary flow rates (mL/min) were measured and saliva samples were collected at time intervals post beverage consumption to measure mucoadhesion to the oral cavity, where protein concentration was analysed by Bradford Assay. Volunteers rated perception and acceptability of WPBs in the main study. WPB consumption resulted in significantly increased protein concentration (p < 0.0001) in saliva samples compared with a control whey permeate beverage. Older adults had significantly lower unstimulated saliva flow (p = 0.003) and significantly increased protein concentration (p = 0.02) in saliva samples, compared with younger adults. Heating of WPB significantly (p < 0.05) increased mouthdrying and thickness perception and reduced sweetness compared with unheated WPB. Mucoadhesion is concluded to be a true phenomenon in WPBs and increases with age.

Consistent Effects of Whey Protein Fortification on Consumer Perception and Liking of Solid Food Matrices (Cakes and Biscuits) Regardless of Age and Saliva Flow.

Although there are numerous high protein products on the market, they are typically not designed with, or for, older consumers. This is surprising considering that dietary guidelines recognise the need for higher protein intake in later life. Protein fortified products are, however, associated with negative sensory attributes and poor consumer acceptance. This paper investigates the extent of mouthdrying sensations within a high protein solid food matrix, along with the effect of age and saliva flow. Solid models using cakes and biscuits, with or without protein fortification, were investigated. The sensory profile and physical properties were analysed and two volunteer studies (n = 84; n = 70) were carried out using two age groups (18-30; 65+). Volunteers rated individual perception and liking of products, and salivary flow rates (mL/min) were measured. Unstimulated salivary flow rates were significantly lower (p < 0.05) in older adults, although this was not found to influence product perception. Protein fortification of cakes and biscuits significantly increased (p < 0.05) perceived mouthdrying, hardness and "off" flavours, and significantly reduced (p < 0.05) melting rate, moistness and liking compared with the control versions. There is a clear need to address negative sensory attributes associated with protein fortification of cakes and biscuits to ensure product suitability for older adults.

Exploiting open source 3D printer architecture for laboratory robotics to automate high-throughput time-lapse imaging for analytical microbiology.

Growth in open-source hardware designs combined with the low-cost of high performance optoelectronic and robotics components has supported a resurgence of in-house custom lab equipment development. We describe a low cost (below $700), open-source, fully customizable high-throughput imaging system for analytical microbiology applications. The system comprises a Raspberry Pi camera mounted on an aluminium extrusion frame with 3D-printed joints controlled by an Arduino microcontroller running open-source Repetier Host Firmware. The camera position is controlled by simple G-code scripts supplied from a Raspberry Pi singleboard computer and allow customized time-lapse imaging of microdevices over a large imaging area. Open-source OctoPrint software allows remote access and control. This simple yet effective design allows high-throughput microbiology testing in multiple formats including formats for bacterial motility, colony growth, microtitre plates and microfluidic devices termed 'lab-on-a-comb' to screen the effects of different culture media components and antibiotics on bacterial growth. The open-source robot design allows customization of the size of the imaging area; the current design has an imaging area of ~420 × 300mm, which allows 29 'lab-on-a-comb' devices to be imaged which is equivalent 3480 individual 1µl samples. The system can also be modified for fluorescence detection using LED and emission filters embedded on the PiCam for more sensitive detection of bacterial growth using fluorescent dyes.