Enhancing synthesis of ethyl lactate in rice baijiu fermentation by adding recovered granular cells.

Ethyl lactate is the most abundant ester in semi-solid rice baijiu fermentation, affecting the flavor of baijiu to a great extent. The present study aimed to investigate the spatial distribution and formation contributor of ethyl lactate by removing the microorganisms and extracellular enzymes from the upper, middle, and lower fermentation broth during the later fermentation stage. The removal of suspended substances by centrifugation did not affect the ethyl lactate content in the top and middle fermentation broth containing free cells, enzymes, and starch particles. After day 5 of fermentation, only the lower fermentation broth containing granular cells attached to the starch could continue to accumulate lactic acid, thereby increasing the ethyl lactate content. The results showed that the chemical reactions were the main contributor to the increased ethyl lactate content at the anaphase of fermentation rather than enzymatic catalysis or microbial metabolism. Sequencing of granular cells revealed the main lactic acid producers at different fermentation stages. Lactobacillus helveticus showed the highest abundance of 94.45-95.40% on day 5, which decreased to 29.58-30.20% on day 15, while Lactobacillus acetotolerans showed the highest abundance of 47.93-49.72% at day 15. Additionally, the granular cells were recovered and used for supplementary inoculation in the next batch, which significantly increased the ethyl lactate content. This study provided a novel strategy for improving the ethyl lactate content in semi-solid baijiu fermentation.

Formation of free radicals in Chi-aroma Baijiu during aging process with fat pork.

Soaking aged fat pork is a special aging process in the production of Chi-aroma Baijiu considered to involve the formation of free radicals. This study aimed to investigate the free radicals' formation pathway in Chi-aroma Baijiu during aged fat pork soaking by using electron paramagnetic resonance (EPR) and spin trapping with 5,5-dimethyl-1-pyrrolin-n-oxide (DMPO). The alkyl radical adducts (DMPO-R) and hydroxyl radical adducts (DMPO-OH) were detected in Baijiu after soaking the fat pork for aging. During the preparation process of aged fat pork, alkoxy radicals adduct (DMPO-RO) were mainly detected since lipid oxidation. Oleic acid and linoleic acid, the two main unsaturated fatty acids in fat pork, produced alkoxy radicals in the oxidation process. The total amounts of spins in linoleic acid and oleic acid after 4-month oxidation treatment increased by 248.07 ± 26.65% and 34.17 ± 0.72% than 0-month. It indicated that the free radicals in aged Chi-aroma Baijiu were mainly derived from the two main unsaturated fatty acids in aged fat pork and linoleic acid had a stronger ability to produce free radicals than oleic acid. Alkoxy radicals (RO·) from fat pork reacted with ethanol in Baijiu to form alkyl radicals (R·). The peroxide bond of hydroperoxides from the oxidation of unsaturated fatty acid was cleaved to form hydroxyl radicals (·OH) that were transferred to Baijiu. The results provide theoretical guidance for the subsequent work of free radicals scavenging.

Promoting lipid oxidation and release of volatiles of pork fat pulp by lipase, blue light with riboflavin in liquor immersion.

The deeply oxidized pork fat (PF) is the key in the production of Chi-aroma Baijiu, a Chinese distilled spirit. Previous studies have not proposed an integrated method to promote lipid oxidation of PF, and the formation of volatiles has not been studied. In this work, an efficient method was established to promote lipid oxidation and release of volatiles of pork fat pulp (PFP) in an integrated treatment for the production of Chi-aroma Baijiu. The results showed that the acid value of PFP by lipase pretreatment (T1) was significantly elevated (p < 0.05), compared to the control (T0). Lipase-blue light-riboflavin-25°C (T2), lipase-open vial-dark-25°C (T3), and lipase-dark-40°C (T4) further promoted lipid oxidation and reached the oxidation level of PFP by F0, while T2 show the best results. The peroxide value of PFP by T2, T3, and T4 was 41.96-, 16.70- and 14.20-fold higher, and the para-anisidine value was 27.13-, 6.94- and 6.70 fold higher than that in T1. The flavor and volatile analyses showed that PFP by T2 had higher response values than T0 at six electronic nose sensors. T2-T4 promoted the release of volatiles and T2 showed the best result. T2 potentially facilitated lipid oxidation, esterification, and substance exchange of PFP, resulting in a higher type (78.57%) and content (114.50%) of volatiles than T0. The integrated treatment with lipase hydrolysis, blue light with riboflavin could promote lipid oxidation and volatiles release to improve production efficiency of deeply oxidized PF. The results would be viably applied to the production of Chi-aroma Baijiu. PRACTICAL APPLICATION: Deeply oxidized pork fat was the key to the production of Chi-aroma Baijiu, while it took a long time (at least 4 months) to prepare. The integrated treatment with lipase hydrolysis, blue light with riboflavin could promote lipid oxidation and volatiles release to improve the production efficiency of deeply oxidized pork fat. The results would be viably applied to the production of Chi-aroma Baijiu.

Accelerating the oxidation of pork fat by illumination and fat oil for the production of Baijiu beverage.

BACKGROUND: Aged pork fat, deeply oxidized pork fat soaked in basic liquor for more than half a year, is an important material in producing Chi-aroma Baijiu (CAB). With the expansion of production scale of CAB, innovative strategies for efficient production of aged pork fat are in great demand. The purpose of this study is to accelerate the lipid oxidation of pork fat and improve the productivity of aged pork fat. RESULTS: Results showed that polyunsaturated fatty acids (PUFAs) were the main reactant; generation reactions of lipid peroxides and free fatty acids (FFAs) were two limiting steps during the preparation of aged pork fat. Processing under illumination could alleviate the first limiting step by increasing the peroxide value and p-anisidine value of pork fat to 16.22- and 28.48-fold higher than control samples and simultaneously the PUFAs were increased to 190.60 ± 0.19 g kg-1 . Soaking in basic liquor with deeply oxidized fat oil could alleviate the second limiting step by transferring FFAs from fat oil into pork fat. With more oxidized PUFAs, the acid value of the pork fat was 7.91-fold higher than that of the control. CONCLUSION: Illumination and deeply oxidized fat oil could alleviate the two rate-limiting steps of lipid oxidation and improve the productivity of aged pork fat significantly. The results are highly applicable in the CAB industry. © 2020 Society of Chemical Industry.

Evaluating the Intoxicating Degree of Liquor Products with Combinations of Fusel Alcohols, Acids, and Esters.

To investigate the effects of fusel alcohols on the intoxicating degree of liquor products, formulated liquors (FLs) were prepared by blending 1-propanol, isobutanol, and isoamyl alcohol with ethanol, organic acids, and corresponding ethyl esters to simulate the formula of traditional Chinese liquors. The prepared FLs were submitted for evaluation of their intoxicating degree (ID). The results showed that the fusel alcohols had a biphasic effect on the IDs of the FLs, depending on the comprehensive coordination of the characteristic minor components. The importance of the suitable ratio of alcohols/acids/esters (RAAE) on the IDs was also revealed. Under an optimal ratio level, the fusel alcohols exhibited negligible effects on the IDs of the FLs. Moreover, the ratio of isoamyl alcohol to isobutanol (IA/IB) showed a strong positive correlation to the IDs of the FLs. This study lays a foundation for the potential application in producing low-ID liquor.

Evaluation of intoxicating effects of liquor products on drunken mice.

Consumption of alcoholic beverages increases the risk of human health problems such as liver, heart and blood vessel diseases. In the present study, the concept of intoxicating degree (ID) is proposed as an index to demonstrate the degree of intoxicating activity for consuming liquor products. A mice model was designed for the evaluation of liquor product IDs. The intoxicating effects of liquor products were investigated by blood alcohol concentrations (BAC) and behaviour abilities of mice including righting reflex, running and forced-swim abilities. A linear regression model between comprehensive drunkenness degree (CD), calculated by integrating BAC and the behaviour abilities, and alcohol-feeding dosages (W), was established (with R2 > 0.9) with a slope factor of K. The ratio of the K values of liquor products to that of purified alcohol could be used to express the ID. For ID values less than 1, the liquor product would have a lower intoxicating effect when the same amount of alcohol content was consumed and vice versa.