Unveiling targeted spatial metabolome of rice seed at the dough stage using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry imaging

Rice (Oryza sativa) seeds contain a variety of metabolites, which not only provide energy for their own growth and development, but also are an important source of nutrition for humans. It is crucial to study the distribution of metabolites in rice seeds, but the spatial metabolome of rice seeds is rarely investigated. In this study, Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) imaging was used to reveal the spatial distribution of free soluble sugars (glucose, fructose, sucrose, and maltose), amino acids (9 essential amino acids and 2 amino acids affecting rice eating quality: L-aspartic acid and L-glutamic acid), and 4 metabolites in the flavonoids synthesis pathway (cinnamic acid, naringenin chalcone, naringenin, and dihydrokaempferol) in rice seed at the dough stage. It was found that the 4 free soluble sugars present similar spatial distribution, mainly distributed in the seed cortex and embryo with high abundance. The majority of amino acids are also concentrated in the rice cortex and embryo, while the others are abundant in the whole seed. Besides cinnamic acid distributed in the seed cortex and embryo, the naringenin chalcone, naringenin, and dihydrokaempferol were also found in the endosperm and had lower content. Furthermore, a colocalization phylogenetic tree according to the spatial distribution imaging of each metabolite was constructed. This study revealed the distribution diversity of metabolites in different segmentations of rice seed at the dough stage, providing clues for the nutritional differences between brown rice and white rice, and serving as a reference for people to target a healthy diet.

Co-Culture Probiotic Fermentation of Protein-Enriched Cereal Medium (Boza)

Objective: Boza is a fermented cereal beverage which is produced by co-culture fermentation of lactic acid bacteria and yeasts. In addition to the nutritional properties of cereals used in the production, it is also suitable to be gaining functional properties by fermenting with probiotic microorganisms.Methods: In this study, protein content of probiotic boza was increased by the addition of gluten, zein and chickpea flour and the volatile compounds formed during co-culture fermentation of the cereal medium with Lactobacillus acidophilus, Bifidobacterium bifidum and Saccharomyces boulardii were determined.Results: It was determined that chickpea added boza provided the highest cell counts of Lactobacillus acidophilus (7.92 logs CFU/g), Bifidobacterium bifidum (7.32 log CFU/g) and Saccharomyces boulardii (3.26 log CFU/g) during storage. With the addition of gluten, the protein content of the sample was enriched four times more when compared with control boza. During fermentation and storage, a total of 36 different compounds were identified with the major compounds as 9,12-octadecadienoic acid, 9-octadecenoic acid, hexadecanoic acid and hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl)ethyl ester. The concentration of volatile compounds generally decreased during storage of samples. According to Principle Cluster Analysis results, enriched protein samples had similar projections due to their fatty acid contents and the main difference was shown in the control sample.Conclusions: The results of this study indicate that chickpea, single or mixture with cereals, can be a good substrate for probiotic microorganism production for acceptance as probiotic foods.

Microbiological and chemical properties of wet tarhana produced by different dairy products

This study investigated the use of kefir, yogurt and their combination in the production of wet tarhana with an aim to increase the nutritional value of the end product. Along with microbiological and chemical properties, the volatile compound composition of wet tarhana was also evaluated. Wet tarhana revealed an increase in the lactic acid bacteria count (LAB) with the addition of kefir. After fermentation, counts of total yeast, LAB, and total mesophilic aerobic bacteria were 7.57, 8.26 and 7.64 log CFU/g, respectively. The values of pH and titratable acidity were measured as 4.78 and 4.68% in terms of lactic acid, respectively, at the end of fermentation. Lactic acid content increased from 3.31 to 10.82 g/kg throughout fermentation. A total of 72 volatile compounds were recorded during fermentation and 44 of these were identified by GC-MS. The most abundant compounds identified in the tarhana samples were hexadecanoic acid and 9,12-octadecadienoic acid. Moreover, ABTS antioxidant activity results of all formulations were measured in the range of 15.86 and 19.31 µmol TE/g at the end of fermentation and it was independent of the fermentation period.