Microbes, bioactive compounds, quality characteristics, and structural changes during the storage of Qingke barley fresh noodles

Abstract

Changes of microbes, bioactive compounds, protein structures, and noodle qualities in Qingke barley (one of the Tibetan barleys) fresh noodles (QBFN) stored at 25°C were evaluated. The results showed that an increase in total plate count (TPC) and total mold count (TMC) occurred after 12 hr, and Pantoea, Erwinia, Bacillus for the bacteria, Penicillium and Aspergillus for the mold became dominant spoilage microorganisms at the end of storage.In addition, according to the microbial growth at 25°C, the microbial growth models were built for both TPC and TMC, and the microbial growth models were well fitted by logistic model, with higher fitting precision. The fitting equations were Y = 3.7642–3.7/[1+(t/26.597)3.1], R2 = 0.9942 and Y = 1.7553–1.7546/[1+(t/19.8)3.4], R2 = 0.9999. Due to the polyphenol oxidization (PPO), the total phenol and flavonoid contents decreased from 77 and 36 mg/100 g to 49 and 18 mg/100 g, respectively. The pH value, color, textural properties, and cooking quality decreased significantly (p < .05). The disulfide (SS) bond content decreased from 2.9 to 1.6 µmol/g, while the free sulfydryl (SH) content increased from 0.9 to 1.3 µmol/g; the cost of a significant reduction in α‐helix induced an increase in the random coil with the deterioration of QBFN. The relative abundance of strong bounded water decreased while the relative abundance of weakly bounded water and free water increased, which indicated the destruction of the structure of protein encapsulating starch in QBFN. Moreover, Pearson correlation analysis showed that changes of TPC, TMC, SS/SH bond content, and water state were also significantly correlated with the appearance, textural properties, and cooking quality of QBFN. Practical applications Investigating changes in microbe diversity, bioactive compound, protein structure, water state, and noodle quality during storage at 25 ± 1°C will help us understand the mechanisms and dynamics of QBFN deterioration. Identification of the dominant microbes that contribute to noodle spoilage and the changes of bioactive compounds help us determine suitable methods to inhibit the growth of microbes and to prevent the loss of bioactive compounds. Moreover, correlation analysis may help us understand the relationship between noodle quality and microbe, water state, and protein structure, and provide a theoretical basis for improving noodle quality.

Different preparation methods affect the phenolic profiles and antioxidant properties of Qingke barley foods

“…The freeze‐dried samples were ground into powders and stored at −80℃ for further study. Both of the free and bound phenolic compounds were extracted according to the method described in our previous research (Tuersuntuoheti, Wang, Wang, et al, 2019).…”

Changes of microbial diversity and volatile compounds in edible and deteriorated Qingke barley fresh noodles stored at 25 °C

“…Qingke barley fresh noodles was prepared according to the methods described in our previous research (Tuersuntuoheti et al ., 2019) the detailed preparation steps have been provided in Appendix S1). The obtained QBFN were put into the sterilised plastic bags and placed at 25 ± 1 °C for further study.…”

“…As noodle deteriorated, the microbial communities, noodle qualities and water state changed, as well as the original unique flavour disappeared (Aoe et al ., 2017). Besides, the disulphide bond content and protein secondary structure also changed (Tuersuntuoheti et al ., 2019).…”

“…The proliferation of microorganisms is one of the critical factors lead to food spoilage, hence it is essential to identify the dominant spoilage microorganisms in foods (Tuersuntuoheti et al ., 2019). Only in this way some preservation methods can be taken to improve the shelf life of food.…”

The protein properties of germinated naked barley with infrared and hot air‐drying and its noodle‐making potential

“…For example, sweet potatoes, taro and naked barley are used as substitutes for refined wheat flour to increase the variety and function of noodle products (Geng et al ., 2016). Noodles made from barley flour are popular among Asian consumers because barley is rich in bioactive substances (Tuersuntuoheti et al ., 2019). Therefore, it is of great value to study the physicochemical and functional properties of barley protein affected by germination and drying methods, as well as the relationship with the noodles.…”