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Processing of dehydrated onion shreds involves contamination during peeling, chopping, and dehydration. Pre-treatments such as blanching, dipping and soaking in chemical solutions reduce the contamination prior to dehydration. Post dehydration treatments include thermal and non-thermal technologies. Hot water blanching in presence of CaCl2 as pre-treatment followed by pulsed light of 2208 ± 0.5 J·cm−2 (2100 V, 120 s) as post-dehydration treatment is employed. Further, the microbial quality and other attributes were assessed during the storage at 25, 30, and 37 °C. The population for aerobic mesophiles and yeasts & molds crossed 5 and 4 log CFU∙g−1, respectively after 30, 27, 19 days of storage at 25, 30, and 37 °C, respectively. Browning index, pyruvic acid, total phenols and flavonoids were most sensitive among the color parameters and bioactive compounds degraded during storage. After 30 days of storage at 25 °C, there was reduction of 82% in ascorbic acid, 39% in pyruvic acid, 93% in thiosulphinate, 50% in total phenolics, and 52% in total flavonoids content of the shreds. At 37 °C, the rate of bioactive degradation was higher and the retention in bioactives after 19 days was 24, 56, 35, 35, and 52% of ascorbic acid, pyruvic acid, thiosulphinate, total phenolics, and total flavonoids content, respectively. The pyruvic acid, ascorbic acid, phenolic and flavonoid content in the onion shreds degraded following first order kinetics, whereas thiosulphinates followed zero order degradation. The shelf-life of the pulsed light decontaminated dehydrated onion shreds was 30, 27, 19 days at 25, 30, and 37 °C, respectively. Pulsed light treatment is recommended for dehydrated onion shreds as an effective technology for microbial inactivation.

Summary: Pink discolouration in a casein hydrolysate prompted an investigation into its formation. When an aqueous solution of the hydrolysate was held at 110 °C, an intense red colour was generated, as was a strong sulphide odour. In a study of colour and amino acids in a hydrolysate solution held at 110 °C for 0–11 h, a substantial cystine loss occurred, with which colour formation was correlated. The red material exhibited affinity for an anion exchange resin, and its analysis by HPLC found ≥7 apparent pigment compounds. These characteristics, along with the free amino acids in the hydrolysate, seem consistent with the formation of thiosulphinate‐derived, conjugated, carboxylated and pyrrole‐based pigment compounds proposed to explain pinking in processed onions. The data raise the possibility that pathways responsible for pink discolouration in the hydrolysate (and possibly to some instances of pink discolouration observed in cheese) are related to those associated with onion pinking. [ABSTRACT FROM AUTHOR]

Pungency is important characteristics of onion and during processing it is generally reduces. Low pressure superheated steam drying (LPSSD) is gaining importance due to energy and product benefits. It results in better retentions of bioactive components. So, in current study onion slices were dried using low pressure superheated steam, and compared with vacuum and hot air drying at different temperature in NIFTEM advance drying unit. Among the selected models, Page’s model gave a better prediction and satisfactorily described drying characteristics of onion slices. The Activation energy was found to be 41.87 kJ/mol in LPSSD. Quality of product, i.e. retention of color, rehydration ratio, thiosulphinate content, total phenol content and antioxidant activity, were better at 70 °C using LPSSD, at 60 °C using VD and HAD, as compared to other drying temperature in respective drying technologies used. Significant differences in quality of the dried product were also observed due to drying temperature in different drying techniques. [ABSTRACT FROM AUTHOR]

Allicin, the active thiosulphinate present in freshly crushed garlic, has potent antimicrobial activity but is chemically labile. As part of a study aimed at producing stable allicin analogues as potential antimicrobial agents, the allicin mimic S-p-tolyl t-butylthiosulphinate was synthesised and complexed with β-cyclodextrin (β-CD). The inclusion complex, β-CD·S-p-tolyl t-butylthiosulphinate·12.5H2O, was characterised by thermal analysis techniques (HSM, TG, DSC), powder X-ray diffraction and single-crystal X-ray diffraction. The inclusion complex is dimeric (space group C2221) with the guest disordered over three positions. Within each β-CD molecule of the dimer, each disordered guest component is located in the host cavity with the t-butyl group protruding slightly from the primary hydroxyl side, while the phenyl ring is situated near the secondary hydroxyl side and the thiosulphinate moiety is centrally located within the host cavity. Stereoselectivity of guest inclusion is implicit in the disordered model, which reflects a 2:1 ratio of S- and R-enantiomers in the β-CD cavity. [ABSTRACT FROM AUTHOR]