Kombucha fortified with Cascade hops (Humulus lupulus L.): enhanced antioxidative and sensory properties

In recent years, there has been a surge in the production of kombucha-a functional beverage obtained via microbial fermentation of tea. However, fresh, unpasteurized kombucha is sensitive to quality deterioration as a result of, among other factors, oxidation. The addition of hops seems to be promising, due to their antioxidative properties, which may improve the stability of kombucha. However, aiming at retaining the highest antioxidative properties of kombucha, it remains unclear at which stage of the production process hops should be added. The study investigated the effect of hop supplementation during kombucha production on the basic physicochemical, antioxidative, and sensory properties of kombucha. Cascade hops in the concentrations 0.5 and 2 g/L were added at the onset of tea infusion and to the fresh, unpasteurized kombucha. The addition of hops (particularly at the pre-fermentation stage of production) led to a significant decrease in radical formation in the produced kombucha measured by electron spin resonance spectroscopy (ESR), which correlated with the higher DPPH antiradical activity and the elevated bitter α-acid content. From the sensory perspective, the post-fermentation addition of hops to kombucha resulted in a significantly higher rating of the overall quality. This enhancement was directly associated with heightened bitterness, increased presence of fruity and citrusy aromas, and a simultaneous reduction in the intensities of acetic and tea-related attributes. The data presented in this study are relevant for kombucha producers, who want to deliver a sensory-novel product in combination with an improved oxidative stability. KEY POINTS: • Hop addition in kombucha production improves the antioxidative activity of the beverage. • Hop α-acids display higher antioxidative properties in kombucha than polyphenols. • Oxidative stability of kombucha fortified with hops depends on the timing of hops addition. • Hop addition enriches the taste and aroma attributes of kombucha.

Effects on beer colloidal stability of full-scale brewing with adjuncts, enzymes, and finings

This study investigated the effects on beer colloidal stability of full-scale brewing with adjuncts, enzymes, and finings. Industrial lager beers were produced solely from barley malt or from barley malt with adjuncts (corn grist and starch syrup or unmalted barley). Various stabilization aids were also used (silica gel, PVPP, proline-specific endoprotease, carrageenan). Predictive shelf-life tests were conducted. We analyzed the content of compounds (proteins and polyphenols) generally related to beer colloidal stability. The results show that the haze-forming potential of the beer during storage can be evaluated based on the coagulable nitrogen content (high molecular weight proteins), rather than the total nitrogen content and polyphenol content. A very strong and statistically significant negative correlation was observed between the concentration of coagulable nitrogen and beer colloidal stability. When brewing was conducted with 49% barley raw material and exogenous proteases, especially proline-specific endoprotease, the coagulable nitrogen content fell and beer colloidal stability improved. The use of corn grist and starch syrup as up to 40% of the total grist resulted in a 30% longer physical shelf life compared to the all-malt beer.

Optimizing brewing conditions for low-temperature green tea infusions: Insights into functional and nutritional properties

In response to growing demand for functional, minimally processed foods and rising energy costs, various brewing conditions for low-temperature green tea production were explored as an alternative to high-temperature processing. Optimal polyphenol extraction was achieved at 85 °C for 30 min using distilled water and finely ground leaves (< 500 μm). Although similar conditions are recommended for tap water, this resulted in a tremendous reduction in both catechin yields and antioxidant capacity (AC), as determined by spectrophotometric and chromatographic analyses. Lowering extraction temperature to 20 °C and brewing for 12 h with distilled water led to exceptionally high AC, along with higher yields of vitamin C, vitamin B2, epicatechin, and epigallocatechin compared to any high-temperature brewing method. Notably, these benefits were evident only when whole leaves were used, rather than tea powder. Further research is needed to address technological challenges for industrial green tea production with distilled water.

Antibacterial efficacy of berry juices against Bacillus cereus relative to their phytochemical composition and antioxidant properties

Ensuring the safety and stability of minimally processed foods using natural preservatives is of great scientific and commercial interest in modern biotechnology. Berry juice supplementation is increasingly recognized within this field. This study investigated the effectiveness of juices from four berry species Aronia melanocarpa, Ribes nigrum, Vaccinium macrocarpon, and Sambucus nigra, against the food pathogen Bacillus cereus. Overall, the antibacterial potency of juice supplements (up to 10% v/v in tryptic soy broth) followed the order of chokeberry > blackcurrant > cranberry > elderberry, with the latter showing no inhibitory effects. Notably, chokeberry and elderberry juices presented lower acidity and significantly greater phenolic contents (p < 0.05) than blackcurrant and cranberry juices did, suggesting that B. cereus susceptibility is not strictly dependent upon low extracellular pH or elevated anthocyanin levels. Instead, it is inferred to correlate with pro-oxidative effects induced directly at the intracellular level. Accordingly, this paper discusses the antioxidative, acidic, and lipophilic attributes of juices and their constituent fractions, including anthocyanins, to elucidate their biopreservative potential. The results of this study increase our understanding of the antibacterial susceptibility of B. cereus.