Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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Author: search.filters.author.Singh HSubject: search.filters.subject.Sugars

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    Impact of protectant uptake on the shelf-life of dried Lacticaseibacillus rhamnosus
    (Elsevier, 2022-01) Priour S; Welman A; Singh H; Ellis A
    To improve the survival of dried probiotics, it is advised to expose the bacteria to protectants prior to processing, allowing equilibration of internal solutes. However, optimal conditions for this exposure remain unclear. This study examined solute uptake by Lacticaseibacillus rhamnosus HN001 (formally known as Lactobacillus rhamnosus HN001) at 4 °C and 20 °C, over exposure times of 0–240 min. The cells were exposed to hyperosmotic solutions of glucose and sucrose, two potential protective sugars, which are metabolisable and have different molecular weights. Sugar uptake was analysed through HPLC, while the impact on cell viability after freeze-drying was examined at 30 °C and 40 °C. The interactions between cell biomolecules and sugars were examined using Nano DSC. Results showed that the sugars were rapidly taken up by the cells, independent of temperature. At 20 °C, glucose was readily metabolised, eventually resulting in loss of cell viability during storage. Conversely, the Nano DSC study revealed interactions between the cells and sucrose, potentially providing some explanation as to the stability of the cells. In conclusion, sugar type and exposure temperature were shown to exert a significant effect on the viability of Lacticaseibacillus rhamnosus. Nano DSC is a promising technique to understand the protectant and cells’ interactions.
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    Low-Cost Sensor for Continuous Measurement of Brix in Liquids
    (MDPI AG, 25/11/2022) Jaywant SA; Singh H; Arif K
    This paper presents a Brix sensor based on the differential pressure measurement principle. Two piezoresistive silicon pressure sensors were applied to measure the specific gravity of the liquid, which was used to calculate the Brix level. The pressure sensors were mounted inside custom-built water-tight housings connected together by fixed length metallic tubes containing the power and signal cables. Two designs of the sensor were prepared; one for the basic laboratory testing and validation of the proposed system and the other for a fermentation experiment. For lab tests, a sugar solution with different Brix levels was used and readings from the proposed sensor were compared with a commercially available hydrometer called Tilt. During the fermentation experiments, fermentation was carried out in a 1000 L tank over 7 days and data was recorded and analysed. In the lab experiments, a good linear relationship between the sugar content and the corresponding Brix levels was observed. In the fermentation experiment, the sensor performed as expected but some problems such as residue build up were encountered. Overall, the proposed sensing solution carries a great potential for continuous monitoring of the Brix level in liquids. Due to the usage of low-cost pressure sensors and the interface electronics, the cost of the system is considered suitable for large scale deployment at wineries or juice processing industries.