READY-TO-EAT SWORDFISH FILLETS SUITABLE FOR DELIVERING PROBIOTIC LACTOBACILLUS PARACASEI IMPC 2.1 CELLS INTO THE HUMAN GUT

The beneficial relationship between the host health and its gut microbiota has led in the last decades to the enormous increase of research and commercial interest in the development of probiotic preparations to manipulate microbiome in helping host physiology or preventing diseases [1]. Producers of functional foods are exploring technological solutions for developing foods supplemented with additional functional benefits but with high level of consumer satisfactions (health-orientated as well as taste-orientated). Many strains belonging to lactic acid bacterial (LAB) species are widely used as probiotics in commercial products since, additionally to functional properties conferred to foods, they may also act as starters establishing a mild fermentation that protects products from deterioration. Particularly, a L. paracasei strain (IMPC 2.1) has been studied and used for the development of innovative patented functional foods based on the association of that probiotic strain with vegetables (olives, artichokes, cabbage etc.) whose commercialization has been authorized by the Italian Ministry of Health [2]. Clinical trials performed on subjects suffering from constipation and healthy subjects demonstrated the efficacy of L. paracasei IMPC 2.1 carried by ready-to-eat artichokes in transiently colonize the human gut thus modulating potentially harmful bacteria, faecal enzyme activity and short chain fatty acid production as well as symptom profile [3]. Currently among probiotic foods, fish products have been rarely investigated as vehicles for probiotic strains in humans, even if they are suitable to sustain viable LAB populations [4]. Therefore our investigation aimed to evaluate the ability of the probiotic L. paracasei strain IMPC 2.1 to survive in marinated ready-to-eat swordfish fillets and to reach, viable, the human gut in an alternate day- based study. Probiotic ready-to-eat swordfish fillets (PR-RTE) were prepared by brining (3% NaCl) fillets for 2 days with live cells of the probiotic strain at 7 log CFU/g; then fillets were drained, seasoned with sunflower seed oil, spiced with parsley and stored under vacuum packing at 4°C in polyethylene trays (shelf life 4 months). The final product, containing more than 7 log CFU/g of the probiotic strain, showed physicochemical characteristics (protein profile and total free amino acid content, pH, aw) similar to those of control-RTE fillets (traditionally processed with an acidic marinade) along shelf life. The probiotic fillets were used in a human feeding study involving 8 volunteers to assess the suitability of the fish matrix in delivering viable cells of the probiotic strain [5]. Participants integrated their dietary intakes throughout the study period with a portion (100 g) of PR-RTE fillets containing about log 9 CFU of probiotic cells. The protocol was approved by a local Scientific and Ethics Committee. The dietary intervention study lasted 27 days and subjects consumed PR-RTE fillets on alternate days for 20 days, with a washout period of 7 days. A good compliance of PR-RTE fillets was registered from all participants. To evaluate the transient gut colonization of the strain, its presence was molecularly ascertained in faecal samples of subjects. Results demonstrated that after consuming 10 portions during 20 days, the probiotic strain was recovered in the faeces of all subjects at concentrations ranging from 6.15 to 7.47 log CFU/g. Interestingly, five subjects resulted to be colonized by the probiotic strain, at levels ranging from 6.30 to 7.74 log CFU/g of faeces, after eating 5 portions of the product (day 10). The probiotic colonization led to an increase, with respect to the start of the study, in the genetic diversity of faecal LAB based on the Shannon diversity index, even though no differences in LAB counts were observed. We can conclude that swordfish fillet is a suitable food carrier for the probiotic strain L. paracasei IMPC 2.1which was able to survive on the fish matrix during a 4-month storage period and to transiently colonize the gut of volunteers after thus providing consumers with a non conventional probiotic food to achieve a Functional Diet.