Volatile compounds, bacteria compositions and physicochemical properties of 10 fresh fermented rice noodles from southern China

Comprehensive improvement of nutrients and volatile compounds of black/purple rice by extrusion-puffing technology

Introduction

Black/purple rice is a pigmented rice variety that contains high levels of anthocyanins, flavonoids, and other valuable bioactive compounds. Owing to its robust anti-inflammatory and antioxidant properties, black/purple rice exerts a beneficial effect on human health. Extrusion puffing technology has emerged as a promising means of improving rice flavor with lesser effect on nutrient content. In this study, metabolomics approach was used to conduct comprehensive metabolomics analyses aimed at examining the impact of extrusion puffing on black/purple rice nutritional value and flavor.

Methods

Firstly, the basic nutrient composition contents and extrudate characteristics of black/purple rice and Extrusion puffed black/purple rice were conducted. Then metabolomics profiling analyses of black/purple rice samples were performed to explore the impact of the extrusion puffing process on nutrient content and bioactive properties, in which we quantitatively determined the flavonoids and evaluated relative contents of volatile compounds.

Results

These analyses revealed that following extrusion puffing, black/purple rice exhibited significant improvements in the content of nutrients including flavonoids, minerals, and proteins together. Extrusion puffing additionally increased the diversity of volatile compounds within black/purple rice.

Discussion

These results suggest that extrusion puffing represents an effective means of substantially improving the functional and nutritional properties of black/purple rice, offering beneficial effects on consumer health. Overall, these data provide novel insights into the quality of extrusion puffed black/purple rice that will guide future efforts to establish how extrusion puffing can alter the nutrient content in a range of foods, thereby supporting the further development of a range of healthy food products.

Different Characteristics of Annealed Rice Kernels and Flour and Their Effects on the Quality of Rice Noodles

In this study, the characteristics of indica rice kernels (IRK) and flour (IRF) annealed in different conditions were evaluated, and the quality of rice noodles made with these IRK and IRF was determined. Native IRK and IRF were annealed in deionized water at a kernel or flour to water ratio of 1:3 (w/v) and temperatures of 50, 55, 60, and 65 °C for 12 and 24 h. Annealing increased the paste viscosity of IRK while decreasing that of IRF. Both annealed IRK and IRF exhibited increases in the gelatinization enthalpy change and relative crystallinity. Annealed IRK gel showed higher hardness, and annealed IRF gel displayed greater springiness. Unlike native rice noodles, annealed IRK noodles exhibited denser pores, while annealed IRF noodles exhibited a looser microstructure. With increasing annealing temperature and time, both annealed IRK and IRF noodles showed enhanced tensile properties. Rice noodles made from IRF annealed at 65 °C for 12 h exhibited a fracture strain of 2.7 times that of native rice noodles. In brief, IRK and IRF exhibited different degrees of susceptibility to annealing. Annealing had more significant effects on IRF than IRK. This study highlights the possibility of using annealed IRK and IRF in rice noodles.

Effects of egg powder on the structure of highland barley dough and the quality of highland barley bread

The influences of egg white (EW), egg yolk (EY) and whole egg (WE) on the structure of highland barley dough and the quality of highland barley bread were explored. The results showed that egg powder reduced G' and G" of highland barley dough, which led to the softer texture of dough and endowed bread with a larger specific volume. EW increased the percentage of β-sheet of highland barley dough, EY and WE promoted the transformation from random coil to β-sheet and α-helix. Meanwhile, more disulfide bonds were formed from free sulfhydryl groups in the doughs with EY and WE. These properties of highland barley dough could help highland barley bread develop a preferable appearance and textural feature. It is worth noting that highland barley bread containing EY has more flavorful substances and a better crumb structure, which were similar to that of whole wheat bread. The highland barley bread with EY received a high score according to the sensory evaluation in consumer acceptance.

Further Interpretation of the Volatile, Microbial Community and Edible Quality of Fresh Fermented Rice Noodles with Different Selected Strains

Understanding bacteria and yeasts can reduce unpredictable changes in fresh fermented rice noodles (FFRN). The effects of selected strains (Limosilactobacillus fermentum, Lactoplantibacillus plantarum, Lactococcus lactis and Saccharomyces cerevisiae) on the edible quality, microbial community, and volatile component of FFRN were studied. The results indicated that the fermentation time could be shortened to 12 h when Limosilactobacillus fermentum, Lactoplantibacillus plantarum, and Lactococcus lactis were added, whereas it still required approximately 42 h after adding Saccharomyces cerevisiae. Only a steady bacterial composition was provided by adding Limosilactobacillus fermentum, Lactoplantibacillus plantarum, and Lactococcus lactis, and only a steady fungal composition was provided by adding Saccharomyces cerevisiae. Therefore, these microbial results indicated that the selected single strains cannot improve the safety of FFRN. However, the cooking loss was decreased from 3.11 ± 0.11 to 2.66 ± 0.13 and the hardness of FFRN was increased from 1186 ± 178 to 1980 ± 207 when it was fermented with single strains. Finally, a total of 42 volatile components were determined by Gas chromatography-ion Mobility Spectrometry and 8 aldehydes, 2 ketones, and 1 alcohol were added during the entire fermentation process. The main volatile components were different during fermentation depending on the added strain, and there was the greatest variety of volatiles in the group with added Saccharomyces cerevisiae.

Understanding the Palatability, Flavor, Starch Functional Properties and Storability of Indica-Japonica Hybrid Rice

The rice quality and starch functional properties, as well as the storability of three YY-IJHR cultivars, which included YY12 (biased japonica type YY-IJHR), YY1540 (intermedius type YY-IJHR) and YY15 (biased indica type YY-IJHR), were studied and compared to N84 (conventional japonica rice). The study results suggested that the three YY-IJHR varieties all had greater cooking and eating quality than N84, as they had lower amylose and protein content. The starch of YY-IJHR has a higher pasting viscosity and digestibility, and there was a significant difference among the three YY-IJHR cultivars. Rice aroma components were revealed by GC-IMS, which indicated that the content of alcohols vola-tile components of YY-IJHR were generally lower, whereas the content of some aldehydes and esters were higher than N84. In addition, YY-IJHR cultivars’ FFA and MDA contents were lower, which demonstrated that YY-IJHR had a higher palatability and storability than those of N84 in fresh rice and rice stored for 12 months. In conclusion, this study suggested that YY-IJHR had better rice quality and storability than N84. PCA indicated that the grain quality and storability of YY12 and YY15 were similar and performed better than YY1540, while the aroma components and starch functional properties of YY-IJHR cultivars all had significant differences.