Development Of Corn-based Symbiotic Yogurt-like Functional Foods

Maize is one of the major crops in Jilin province. Jilin produces the more corn than any other provinces in China. Corn has been used as a staple plant food or industrial ingredient for many years. However, value-added corn-based food products are still limited in Jilin province and beyond. In this study, a corn-based symbiotic yogurt-like product(CSYP) was developed using dry grains of corn as the major raw material. The corn base was prepared through smashing, extrusion, grinding processes. Then sugar, stabilizers, polymerized whey protein, soy protein isolate, and inulin were added to the base and a yogurt starter containing Lactobacillus plantarum was inoculated to the base. The mix was fermented at 35℃ for 6 h.(1) By measuring water solubility index and water absorption index of corn powder, the extrusion process conditions were determined as follows: barrel temperature 130℃, material moisture adjusted to 15%, after sieving through 80 mesh and the powder was extruded. The extruded material was soaked in the water and mixed by a colloid mill twice. Based on the centrifugal sedimentation rate and static observation, glycerol mono stearate and sucrose ester in the ratio of 1:1 and 0.2% of the stabilizers was added.(2) According to the viscosity of the material and the soluble solids content, 8% solution of the extruded material containing 5% and 2% glucose; optimized by single factor design, the combination of Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus plantarum were used as the corn based yogurt starter cultures. Lactobacillus bulgaricus and Streptococcus thermophilus adding amount was 0.006%(w/v), Lactobacillus plantarum inoculation amount was of 0.018%(w/v). Then 0.75% of the soy protein isolates was added to the corn yogurt mix to increase the protein content and the texture. Polymerized whey protein, pectin, xanthan gum and carrageenan were studied as stabilizers and found that 0.3% polymerized of whey protein and 0.09% xanthan gum resulted in good texture, viscosity and water holding characteristics.(3) Determination of chemical composition of the symbiotic corn yogurt were(%): protein content(1.12±0.03), fat(0.3±0.05), ash(0.16±0.02), carbohydrates(15.14±0.19), and total solids(17.13±0.31), respectively. During the 7 weeks shelf life studies, the symbiotic corn yogurt p H value decreased from 4.5±0.03 to 3.88±0.13, the population of Lactobacillus plantarum ranged from 7.87±0.09 log CFU/ml to 7.1±0.14 log CFU/ml at end of the storage, higher than the national requirements for probiotic fermented foods. There was no mold, yeast, coliform detected in the new product during the first 4 weeks.