Effects of different modified starches and gums on the physicochemical, functional, and microstructural properties of tapioca pearls.

The effects of different modified starch and gums on the physicochemical, functional, and microstructural properties of tapioca pearls were investigated. The addition of starch acetate (SA) and carboxymethylcellulose (CMC) improved the springiness, hardness, cooking properties, and overall acceptability of pearls. Samples added with CMC presented higher peak viscosities, breakdown viscosities, onset gelatinization temperature, and lower enthalpy of gelatinization values compared to control pearls. Furthermore, Rheology and LF-NMR results indicated that all five kinds of modifiers promoted the formation of tighter network structures in products. SEM showed that the addition of SA and hydroxypropyl distarch phosphate (HDP) could fill the voids in the internal gel network of the pearls, thus promoting the formation of a continuous phase network. This study proved SA, HDP, and CMC as modifiers could have tremendous potential to improve the quality of pearls before and after cooking.

Ordered structural changes of retrograded starch gel over long-term storage in wet starch noodles.

Temperature-induced structural variations of retrograded starch gel during long-term storage were investigated in a real food system (wet starch noodles). Fresh starch noodles presented a B-type XRD pattern containing 8.82% crystallinity and 16.04% double helices. In the first 2 weeks, double helices of starch chain formed long-range ordered structure leading to increased crystallinity, and such structural transformation was positively correlated with increasing storage temperature (from 4 °C to 35 °C) and storage time. However, with the extension of storage time to 12 weeks, the disorganization of supra-molecular structure was likely to be observed by decreased crystallinity, double helix and water mobility. Besides, we propose that the area and intensity of Raman band at 2910 cm-1 can be a good indicator for evaluating perfection of crystallinity in starch noodles. These results contributed to a better understanding of mechanisms underlying molecular order changes of retrograded starch gel product during long-term storage.

Evaluation of cooking performance, structural properties, storage stability and shelf life prediction of high-moisture wet starch noodles.

Cooking performance, micro- and molecular structure, storage stability and shelf-life prediction of high-moisture wet starch noodles (SN) were investigated. SEM images revealed that compared to dried SN, cooked wet SN had more evenly honeycomb-like network with smaller size of pores, indicating stronger interaction among molecules and causing favorable cooking performance. XRD and ATR-FTIR results evidenced that wet SN contained more complete crystallites and higher proportion of crystalline region. During storage, the quality decay of wet SN was mainly associated to the increment of total aerobic viable count (TAVC), titrable acidity and amylase, as well as the decreased textural hardness, overall acceptability and lightness. Based on TAVC, titrable acidity and overall acceptability, predicted shelf-life of vacuum-packed wet SN at 25 °C was 15.31, 21.54 and 16.65 weeks respectively, with relative error all within 20%, proving that the validated model could be an effective tool for monitoring the shelf-life of wet SN.

Dissimilarity in sensory attributes, shelf life and spoilage bacterial and fungal microbiota of industrial-scale wet starch noodles induced by different preservatives and temperature.

Shelf life, storage stability and microbial growth of wet starch noodles during storage were investigated, and spoilage microbiota was also analyzed to further reveal the decisive factor shaping the microbial community. Sensory analysis and microbiological results indicated that starch noodles treated with sodium dehydroacetate and stored at 4 °C could effectively delay the moldy decay and extend the shelf-life to 50 days, as compared to control and other treatments. In wet starch noodles, molds were found to have a higher spoilage potential than bacteria and yeasts. 16S rDNA sequencing revealed that preservatives, rather than temperature, could cause the significant difference (PERMANOVA p = 0.001) of spoilage bacterial community among samples and sodium dehydroacetate could markedly reduce the bacterial diversity. ITS rDNA sequencing results demonstrated that temperature was the decisive factor in shaping fungal spoilage microbiota (Mantel test r = 0.413, p = 0.002). Besides, Spearman correlation analysis illustrated that the abundance of some microorganisms such as Pseudomonas, Aspergillus and Penicillium were found to be significantly correlated with pH or temperature. These findings provide guiding information in the selection of preservatives and environmental condition for this high-moisture starch noodles.