Effects of Different Probiotics on the Volatile Components of Fermented Coffee Were Analyzed Based on Headspace-Gas Chromatography-Ion Mobility Spectrometry

Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was used to study the effects of four kinds of probiotics on the volatile components of fermented coffee. The fingerprints showed that 51 compounds were confirmed and quantified, including 13 esters, 11 aldehydes, 9 alcohols, 6 ketones, 3 furans, 5 terpenes (hydrocarbons), 2 organic acids, 1 pyrazine, and 1 sulfur-containing compound. After fermenting, the aroma of the green beans increases while that of the roasted beans decreases. After roasting, the total amount of aroma components in coffee beans increased by 4.48-5.49 times. The aroma differences between fermented and untreated roasted beans were more significant than those between fermented and untreated green beans. HS-GC-IMS can distinguish the difference in coffee aroma, and each probiotic has a unique influence on the coffee aroma. Using probiotics to ferment coffee can significantly improve the aroma of coffee and provide certain application prospects for improving the quality of commercial coffee beans.

Low-energy X-ray irradiation: A novel non-thermal microbial inactivation technology

Over the last several decades, food irradiation technology has been proven neither to reduce the nutritional value of foods more than other preservation technologies, nor to make foods radioactive or dangerous to eat. Furthermore, food irradiation is a non-thermal food processing technology that helps preserve more heat sensitive nutrients than those found in thermally processed foods. Conventional food irradiation technologies, including γ-ray, electron beam and high energy X-ray, have certain limitations and drawbacks, such as involving radioactive isotopes, low penetration ability, and economical unfeasibility, respectively. Owing to the recent developments in instrumentation technology, more compact and cheaper tabletop low-energy X-ray sources have become available. The generation of low-energy X-ray, unlike γ-ray, does not involve radioactive isotopes and the cost is lower than high energy X-ray. Furthermore, low-energy X-ray possesses unique advantages, i.e., high linear energy transfer (LET) value and high relative biological effect (RBE) value. The advantages allow low-energy X-ray irradiation to provide a higher microbial inactivation efficacy than γ-ray and high energy X-ray irradiation. In the last few years, various applications reported in the literature indicate that low-energy X-ray irradiation has a great potential to become an alternative food preservation technique. This chapter discusses the technical advances of low-energy X-ray irradiation, microbial inactivation mechanism, factors influencing its efficiency, current applications, consumer acceptance, and limitations.

Effects of thermal and nonthermal processing technology on the quality of red sour soup after storage

In the present study, we investigated the effects of thermal preservation, such as pasteurization, and nonthermal preservation, including irradiation, sodium dehydroacetate (SDHA), and nisin, on the quality of red sour soup after storage. Single-factor experiments were used to optimize the parameters of different processing technologies, and the best irradiation dose and heating temperature were 4 kGy and 85℃, respectively. The optimal additive amounts of SDHA and nisin were 150 mg/500 g. During the shelf storage experiment, prepared red sour soup was stored at room temperature in the glass bottles, and further analyses were carried out up to 5 weeks of storage. The quality of red sour soup was evaluated by microflora and sensory analysis. The results showed that Lactobacillus, Streptomyces, Pediococcus, Pichia, Kazachstania, and Candida were the main microorganisms in all samples, and there were no harmful microorganisms. The sensorial attributes were observed, including different parameters, such as odor, organic acid content, color, taste, texture, apparent viscosity, and thixotropy. All of the data showed that the irradiated groups were more dramatically changed compared with the other groups, while these changes did not directly affect the sensory quality of the products. Consequently, irradiation could be used as an ideal quality preservation method for the red sour soup to reduce the impact of heat treatment and chemical additives on the quality of characteristic food.