Effect of date palm coproducts and annatto extract on lipid oxidation and microbial quality in a pork liver pâté.

Dates are an interesting source of bioactive compounds, and coproducts from the date industry are of potential use in the manufacturing of meat products. In the present research, spreadable pork liver pâtés were made using fresh date coproducts (2.5% and 7.5%) as a potential functional ingredient and an ethanolic annatto extract (128 mg/kg) as colorant. The effect of these 2 ingredients on the lipid oxidation and microbial quality of the pâtés was assessed during 21 d of storage. The pâtés containing 7.5% date paste were seen to have the highest content of phenolic compounds during storage. The combination of 2.5% date paste and annatto protected pâtés against lipid oxidation throughout the 21 d of storage, thiobarbituric acid-reactive substances values being 0.47 mg MDA/kg at the end of this period, while other combinations increased oxidation compared to the control pâté. The control and those made with 2.5% date paste alone showed the highest counts of mesophilic aerobic bacteria, while the addition of annatto and/or 7.5% date paste reduced this count. The results suggest that a combination of both ingredients is necessary to reduce oxidation and microbial growth, but whereas the concentration of 2.5% is more appropriate to reduce oxidation, the combination with 7.5% date paste reduces the microbial counts. Both ingredients could have an opportunity of valorization in the meat industry for improving the quality.

First Report of Alternaria alternata Causing Postharvest Black Spot of Fresh Date Palm Fruit in Spain.

Commercial production of date palm fruit (Phoenix dactylifera L.) for fresh consumption has increased in the grove of Elx (Alacant Province, southeast Spain) after the successful development of tissue culture technologies and induced ripening and cold storage protocols. In a survey of losses after harvest, disease symptoms consisting of superficial, small, and firm black spots irregularly distributed throughout the fruit skin were observed in commercially handled and cold-stored fruit. At room temperature, superficial lesions expanded and produced dark mycelium. The potential causal agent was transferred to potato dextrose agar (PDA), incubated at 25°C in darkness, and subcultured on PDA. The identification was performed at the Spanish Type Culture Collection (CECT, University of Valencia, Spain) using colony morphology on PDA and malt extract agar at 26 or 37°C. At 26°C, the fungus rapidly produced cottony white mycelium that turned olivaceous and dark brown to black. Conidiophores were simple, straight or bent, with plain walls. Conidia were brown, obpyriform to ellipsoid (average 22 to 39 × 8 to 15 µm; n = 50), with both transversal and longitudinal septa, often observed in branched chains with more than 5 conidia. Growth occurred at 37°C. The identification of Alternaria alternata (Fr.:Fr.) Keissler was confirmed by the amplification and subsequent sequencing with the primers NL1 and NL4 of the region D1/D2 in the 5' end of the 28S rRNA gene of the isolate IVIA DAA-4 (GenBank Accession No. JX987100). A BLAST search showed 100% identity with A. alternata strain DAOM 216376 (JN938894). Selected healthy 'Medjool' dates were surface disinfected by dipping them for 2 min in a 0.5% sodium hypochlorite solution and thoroughly rinsed with fresh water. To fulfill Koch's postulates, 20 µl of a spore suspension at 1 × 105 spores per ml prepared from 7-day-old colonies grown on PDA were placed in fresh skin wounds made in disinfected fruit using a sterile stainless steel rod with a probe tip 1 mm wide and 2 mm in length (one wound per fruit; three humid chambers with nine fruits each). Wounded but not inoculated fruit were used as controls (one humid chamber with nine fruit). While disease symptoms were observed on all fruit inoculated with A. alternata (average black spots of 3, 6, and 12 mm after 4, 7, and 10 days of incubation at 20°C), no decay was observed on any of the control fruit. Reisolation of the fungus was performed from 10 infected dates and it was positive in all cases. A. alternata has been reported to cause date palm fruit disease in Israel (1) and Egypt (2), whereas Alternaria spp. have been cited in California (3) and Iran (4). To our knowledge, this is the first report of A. alternata causing date palm fruit rot in Spain. References: (1) R. Barkai-Golan et al. Hassadeh 69:1446, 1989. (2) H. M. El-Deeb et al. Acta Hort. 736:421, 2007. (3) H. S. Fawcett and L. J. Klotz. University of California Bulletin 522, 1932. (4) F. Karampourland and H. Pejman. Acta Hort. 736:431, 2007.

First Report of Penicillium expansum Causing Postharvest Blue Mold of Fresh Date Palm Fruit (Phoenix dactylifera) in Spain.

A survey of postharvest losses of commercially handled and cold-stored fruit of fresh date palm (Phoenix dactylifera L.), cvs. Medjool and Hayani, was conducted in the 2009 and 2010 seasons in the grove of Elx (Alacant Province, Southeast Spain). Disease symptoms consisting of circular, light brown, soft spots located in any part of the fruit skin were observed in 2 to 5% of the fruit. At room temperature, the lesions expanded rapidly and blue mold symptoms were apparent. The potential causal agent (isolate IVIA NiAA-2) was transferred to PDA and incubated at 25°C. The identification was performed at the Spanish Type Culture Collection (CECT, University of Valencia, Spain) based on colony morphology of the isolate grown on Czapeck yeast extract agar (CYA) and malt extract agar (MEA) at 26°C. Colonies were circular (average diameter of 40 mm at 7 days), radially sulcate, with dense velvety white mycelium, and very abundant, bluish green conidia. The underside of the plates showed light brown and pale green colonies on CYA and MEA, respectively. On CYA, but not on MEA, a light yellow exudate was produced and a brownish pigment diffused into the medium. At 5 and 37°C on CYA, white microcolonies and no colonies were observed, respectively. Conidia were ellipsoidal to subglobose, smooth and thin walled, measuring 3.0 to 3.5 × 2.5 to 3.0 µm (n = 50) (4). Based on these morphological characteristics, the isolate IVIA NiAA-2 was tentatively identified as Penicillium expansum L. To confirm the identity, we amplified and sequenced the rDNA internal transcribed spacer (ITS) region with primers ITS1 and ITS4 (GenBank Accession No. KC169942). A BLAST search showed 99% identity and 100% query coverage with P. expansum strain NRRL 6069 (DQ339562) (2). Selected healthy dates cv. Medjool were surface disinfected by dipping in 0.5% sodium hypochlorite for 2 min followed by thorough rinsing in deionized water. Pathogenicity was tested by pipetting 20 µl of a spore suspension (1 × 106 spores per ml), prepared from 7-day PDA cultures, onto fresh skin wounds, which were made on disinfected fruit using a sterile, stainless steel rod with a probe tip 1 mm in width × 2 mm in length (one wound on each of nine dates, incubated in one humid chamber). Disinfected, wounded, and non-inoculated dates were used as controls. The procedure was repeated three times. Disease symptoms were observed on all inoculated fruit (average lesion size of 6, 15, and 22 mm after 4, 7, and 10 days of incubation at 20°C, respectively) and P. expansum was consistently reisolated, thereby fulfilling Koch's postulates. No decay was observed on any of the non-inoculated fruit. Unidentified species of Penicillium have been reported to cause date palm fruit rot (1,3). To our knowledge, this is the first report of P. expansum causing postharvest decay of date palm fruit in Spain. References: (1) M. Djerbi. Diseases of the Date Palm. FAO Regional Project, Rome, 1983. (2) M. A. Dombrink-Kurtzman. Antonie Van Leeuwenhoek 91:179, 2007. (3) S. Ibrahim and M. A. Rahma. Bayero J. Pure Appl. Sci. 2:127, 2009. (4) R. A. Samson et al. Introduction to Food-Borne Fungi. Centraalbureau voor Schimmelcultures, Baarn, the Netherlands, 1995.