Volatile Analysis of Ground Almonds Contaminated with Naturally Occurring Fungi

Abstract

Aflatoxigenic aspergilli inflict major economic damage to the tree nut industry of California, with the highest negative impact to almonds. Aspergilli and fungi in general are known to emit volatiles in varying quantity and composition dependent upon their growth media. The goal of the study was to determine the volatile emission of whole and blanched almonds that had been picked out and labeled as inedible by processors. The aflatoxin content and number of colony forming units of each sample were also determined. A total of 23 compounds were consistently detected and identified. Several volatiles from the blanched almonds demonstrated significant increases when compared to the emissions of whole almonds. Several of these volatiles are considered fatty acid decomposition products and included hexanal, heptanal, octanal, nonanal, 3-octen-2-one, tetramethylpyrazine, and decanal. The almond samples investigated were characteristic of a typical postharvest environment and illustrative of potential contamination within a stockpile or transport container. Volatiles indicative of fatty acid decomposition were predominant in the samples that underwent some form of blanching. The emission amounts of hexanal, heptanal, octanal, and hexanoic acid increased 3-fold in samples contaminated with aflatoxin; however, due to variability between samples they could not be considered as indicator volatiles for aflatoxin content. The emission profile of volatiles from almond kernels contaminated with naturally occurring aspergilli and associated fungi is heretofore unreported.

Monitoring the oxidative stability and volatiles in blanched, roasted and fried almonds under normal and accelerated storage conditions by DSC, thermogravimetric analysis and ATR‐FTIR

“…A total of 23 volatile compounds were identified in raw almonds on day 0 (Table ). These results are in good agreement with those reported by previous works . In order to remove almond skin, commercial blanching involves the exposure of the almond kernel to water at 90–100°C for two or more minutes ; so, it can be considered a smooth treatment which allows almonds to maintain their initial aroma profile.…”

Distribution and Mycotoxigenic Potential of Aspergillus Section Nigri Species in Naturally Contaminated Almonds

“…In contrast, in tw o separate raisin vineyard studies, A. niger and A. awamori strains were recovered more frequently than were A. tubingensis strains (50 versus 45% , and 68 versus 25% , respectively) (25, unpublished data). No A. flavus or A. parasiticus strains were isolated from raisin samples, but unblanched almonds contained significant A. flavus and A. parasiticus populations (7). Together, these results suggest m ajor differences in the fungal com munities on these two crops.…”

“…OTA was recovered from samples 10, 11, and 15 at 0.42, 1.21, and 0.59 ng/g, respectively. The presence of OTA did not correlate with the concentration of aflatoxins detected in these same samples (7). The low frequency and extent of OTA contamination and the absence of detectable A. carbonarius populations suggest that in these samples OTA contamination was caused by uncharacterized populations of other OTAproducing Aspergillus species such as A. alliaceus, A. ochraceus, A. melleus, or other species in Aspergillus section Circumdati (4,9).…”

“…In a recent study of volatile compounds released from almond pick-out samples, Beck et al (7) found high aflatoxin levels and recovered Aspergillus Jlavus and Aspergillus parasiticus from these nuts. During that study, the authors also found a high incidence of black-spored aspergilli, members of Aspergillus section Nigri (6).…”

Electrophysiological responses of male and female Amyelois transitella antennae to pistachio and almond host plant volatiles

“…This apparent trend of the males' higher response to volatiles that are present in or derived from further stages of nut decay (fungal or oxidative) would need to be further investigated for their semiochemical activity. Several of the volatiles noted in Figure 3 were also detected in wet pistachio and almond mummies (Beck et al, 2014b), as well as from fungal-contaminated almond kernels (Beck et al, 2011b). One possibility for this could be that males are attracted to decayed nuts, such as mummies from which A. transitella emerge (Kuenen & Siegel, 2010).…”