Novel Functional Grape Juices Fortified with Free or Immobilized Lacticaseibacillus rhamnosus OLXAL-1

Abstract

During the last decade, a rising interest in novel functional products containing probiotic microorganisms has been witnessed. As food processing and storage usually lead to a reduction of cell viability, freeze-dried cultures and immobilization are usually recommended in order to maintain adequate loads and deliver health benefits. In this study, freeze-dried (free and immobilized on apple pieces) Lacticaseibacillus rhamnosus OLXAL-1 cells were used to fortify grape juice. Juice storage at ambient temperature resulted in significantly higher (>7 log cfu/g) levels of immobilized L. rhamnosus cells compared to free cells after 4 days. On the other hand, refrigerated storage resulted in cell loads > 7 log cfu/g for both free and immobilized cells for up to 10 days, achieving populations > 109 cfu per share, with no spoilage noticed. The possible resistance of the novel fortified juice products to microbial spoilage (after deliberate spiking with Saccharomyces cerevisiae or Aspergillus niger) was also investigated. Significant growth limitation of both food-spoilage microorganisms was observed (both at 20 and 4 °C) when immobilized cells were contained compared to the unfortified juice. Keynote volatile compounds derived from the juice and the immobilization carrier were detected in all products by HS-SPME GC/MS analysis. PCA revealed that both the nature of the freeze-dried cells (free or immobilized), as well as storage temperature affected significantly the content of minor volatiles detected and resulted in significant differences in the total volatile concentration. Juices with freeze-dried immobilized cells were distinguished by the tasters and perceived as highly novel. Notably, all fortified juice products were accepted during the preliminary sensory evaluation.

Effect of Immobilized Pediococcus acidilactici ORE5 Cells on Pistachio Nuts on the Functional Regulation of the Novel Katiki Domokou-Type Cheese Microbiome

“…The incorporation of immobilized probiotic cells resulted in higher cell viability compared to the cheese sample fortified with free cells, indicating the positive impact of cell immobilization on the maintenance of high cell loads. These results are in accordance with previous studies that demonstrated the enhancement of cell survival by cell immobilization [4,32,33]. Indeed, the incorporation of immobilized L. casei ATCC 393 on apple pieces and casein in yogurt resulted in cell loads > 7 logcfu/g up to 28 days of storage [32], while Shehata et al (2022) reported that soft cheese with immobilized L. paracasei cells on wheat bran exhibited high cell loads (>7.5 logcfu/g) after 30 days of storage [33].…”

“…The acids found at increased concentrations in the KFP and KIP samples were sorbic, octanoic and decanoic acid, which were at higher amounts in the KFP samples-results that are in accordance with previous studies in dairy products fortified with probiotics [33,34]. Among alcohols, the most abundant were 3-methyl-1-butanol and 2-phenylethanol in all samples and are described as exerting malt notes and burnt aroma [4]. Carbonyl compounds detected in cheese samples belong to aldehydes and ketones, but aldehydes were in low concentrations due to their reduction to alcohols [35].…”

“…Total aerobic counts (TAC), total psychrophilic counts, lactococci, yeasts/molds, staphylococci, Enterobacteriacae, coliforms and L. monocytogenes were determined as described by Nikolaou et al [4].…”

“…However, maintaining such high cell loads during food processing and storage consists of a real bottleneck for the food industry. Hence, cell immobilization is recommended as an alternative solution to overcome such obstacles, as it has been reported that it may enhance cell survival rates and ensure cell stability [3,4]. In addition, considering that the food industry favors dried products due to their prolonged shelf life, ease of storage and transportation, and cost-effectiveness resulting from the elimination of refrigeration needs, freeze-drying is commonly employed for delicate ingredients that require special care [5].…”

Special Issue “Probiotics, Prebiotics and Functional Foods: Health Benefits and Biosafety”

“…Nikolaou et al [ 12 ] investigated freeze-dried Lacticaseibacillus rhamnosus OLXAL-1 cells, free and immobilized on apple pieces, to fortify grape juice. The results showed that refrigerated storage resulted in cell loads > 7 log cfu/g for both free and immobilized cells for up to 10 days, achieving populations > 10 9 cfu per share, with no noticeable spoilage.…”