In light of the growing interest in products with reduced sugar content, there is a need to consider reducing the natural sugar concentration in juices while preserving the initial concentration of nutritional compounds. This paper reviewed the current state of knowledge related to mixing juices, membrane processes, and enzymatic processes in producing fruit juices with reduced concentrations of sugars. The limitations and challenges of these methods are also reviewed, including the losses of nutritional ingredients in membrane processes and the emergence of side products in enzymatic processes. As the existing methods have limitations, the review also identifies areas that require further improvements and technological innovations.

The study aimed to assess the nutritional properties of fruit juices using the microwave flow pasteurization (MFP) method. The innovative spray deaeration process was also employed at two different temperatures, 25 °C and 50 °C, with three rotational speeds for the spray nozzle: 150, 450, and 750 rpm. The research focused on two not-from-concentrate (NFC) juices: apple–peach and apple–chokeberry. The innovative MFP method demonstrated significant results over 12 months of storage: no presence of Listeria monocytogenes or Salmonella spp. bacteria was detected. Polyphenol oxidases (PPOs) were inactivated, while peroxidase (POD) activity in apple–peach juice was minimal. The total polyphenol content (TPC) in the juices gradually decreased over storage time, but MFP resulted in a slower degradation of TPC than traditional pasteurization (TP). Additionally, anthocyanin and carotenoid content gradually decreased during storage time. Still, with MFP, higher concentrations of these compounds were noted up to 4 and 6 months of storage in apple–peach and apple–chokeberry juices, respectively, than with TP. The research findings indicate that MFP may be a suitable and promising technique for preserving high-quality juices with superior retention of essential nutrients. However, the recommended storage time should be at most four months.

The research material consisted of not from concentrate (NFC) apple juice, which underwent innovative processes of spray deaeration and flow microwave pasteurization. Traditional commercially available pasteurization was the control. Deaeration was conducted at two different temperatures (25 °C and 50 °C) and three rotational speeds of the spray disc (150 rpm, 450 rpm, 750 rpm). Flow microwave pasteurization was carried out at 90 °C with a flow rate of 5.8 L/min. Deaeration at a temperature of 25 °C and a rotation speed of 150 rpm resulted in a significant reduction in oxygen levels in the juice to 0.9 mg/L. Microwave pasteurization led to an almost 100% reduction in oxidoreductases activity (PPO, POD). Immediately after the process, microwave-pasteurized juice exhibited better stability of the total polyphenol content, with a TPC of 73.8 mg/100 mL. Microwave pasteurization caused a threefold increase in antioxidant capacity (176.8 µM/100 mL) compared to fresh juice. The color of microwave-pasteurized juice was more appealing than that of traditionally pasteurized juice.

Z uwagi na negatywny wpływ nadmiernego spożycia cukru na zdrowie człowieka, Światowa Organizacja Zdrowia zaleca ścisłe kontrolowanie jego ilości w codziennej diecie. Wychodząc naprzeciw tym wytycznym, AIJN wraz z Komisją Europejską rozpoczęły działania zmierzające do prawnego usankcjonowania nowej kategorii produktów – soków owocowych o obniżonej zawartości cukrów. Obecnie trwają prace nad nowelizacją Dyrektywy Sokowej. Będzie ona obejmowała dodanie wymagań dla soków o obniżonej zawartości cukrów. W artykule omówiono szereg metod pozwalających na redukcję cukrów w sokach owocowych, m.in. zmniejszenie stężenia cukru poprzez dodanie innego soku o znacznie niższej wartości Brix, nanofiltrację, fermentację etanolową i mlekową czy wykorzystanie specyficznych enzymów.