Quality evaluation of raw ground almond kernels (Prunus dulcis): Effect of active and modified atmosphere packaging, container oxygen barrier and storage conditions

The present study investigated the effect of active and modified atmosphere packaging, container oxygen barrier and storage conditions on quality retention of raw ground almonds. Ground almond kernels were packaged in: a) polyethylene terephthalate//low density polyethylene (PET//LDPE), and b) low density polyethylene/ethylene vinyl alcohol/low density polyethylene (LDPE/EVOH/LDPE), under N₂ or with an oxygen absorber and stored either under fluorescent light or in the dark at 4 or 20 °C for a period of 12 months. Quality parameters monitored were: peroxide value (PV), hexanal content, color, fatty acid composition and volatile compounds. Of the sensory attributes color, texture, odor and taste were evaluated. PV ranged between 0.26 for fresh almonds and 19.98 meq O₂/kg oil for almonds packaged in PET//LDPE pouches under N₂ exposed to light at 20 °C after 12 months of storage. Respective values for hexanal were < 28.5 µg/kg and 9.38 mg/kg. Polyunsaturated fatty acids (PUFA) and saturated fatty acids (SFA) increased with a parallel decrease of monounsaturated fatty acids (MFA) after 12 months of storage in samples stored with the oxygen absorber while in samples packaged in PET//LDPE under N₂, a decrease in PUFA and MUFA with a parallel increase in SFA was recorded. Likewise, volatile compounds such as aldehydes, ketones, alcohols, acids, alkanes and aromatic hydrocarbons increased during storage indicating enhanced lipid oxidation. Color parameters L, a and b remained unaffected in all treatments including the oxygen absorber while under a N₂ atmosphere L parameter showed a small but statistically significant (p < 0.05) decrease with a parallel increase (p < 0.05) of a and b values after 12 months of storage. The most pronounced color changes occurred for samples in PET//LDPE pouches irrespective of lighting conditions at 20 °C. Raw ground almonds retained acceptable quality for ca. 6–7 months packaged in PET//LDPE and ca. 8 months packaged in LDPE/EVOH/LDPE pouches under N₂ irrespective of lighting conditions at 20 °C while at 4 °C shelf life was extended by an additional month as compared to storage at 20 °C. Use of the oxygen absorber provided a shelf life of at least 12 months for all samples irrespective of container oxygen barrier, lighting conditions and storage temperature.

Industrial relevance

The use of oxygen absorbers is very effective in extending the shelf life of ground almonds commercially for at least 12 months irrespective of packaging material barrier to O₂, lighting conditions and storage temperature.     

Effect of irradiation, active and modified atmosphere packaging, container oxygen barrier and storage conditions on the physicochemical and sensory properties of raw unpeeled almond kernels (Prunus dulcis)

BACKGROUND: The present study investigated the effect of irradiation, active and modified atmosphere packaging, and storage conditions on quality retention of raw, whole, unpeeled almonds. Almond kernels were packaged in barrier and high‐barrier pouches, under N₂ or with an O₂ absorber and stored either under fluorescent lighting or in the dark at 20 °C for 12 months. Quality parameters monitored were peroxide value, hexanal content, colour, fatty acid composition and volatile compounds. Of the sensory attributes colour, texture, odour and taste were evaluated. RESULTS: Peroxide value and hexanal increased with dose of irradiation and storage time. Irradiation resulted in a decrease of polyunsaturated and monounsaturated fatty acids during storage with a parallel increase of saturated fatty acids. Volatile compounds were not affected by irradiation but increased with storage time indicating enhanced lipid oxidation. Colour parameters of samples remained unaffected immediately after irradiation. For samples packaged under a N₂, atmosphere L* and b* values decreased during storage with a parallel increase of value a* resulting to gradual product darkening especially in irradiated samples. CONCLUSION: Non‐irradiated almonds retained acceptable quality for ca. 12 months stored at 20 °C with the O₂ absorber irrespective of lighting conditions and packaging material oxygen barrier. The respective shelf life for samples irradiated at 1.0 kGy was 12 months packaged in PET‐SiOx//LDPE irrespective of lighting conditions and 12 months for samples irradiated at 3 kGy packaged in PET‐SiOx//LDPE stored in the dark. Copyright © 2010 Society of Chemical Industry     

Effects of γ-irradiation on the α-tocopherol and fatty acids content of raw unpeeled almond kernels (Prunus dulcis)

The present study evaluated fatty acid composition and α-tocopherol content of almond as a function of irradiation dose in order to determine dose levels causing minimal undesirable changes to almonds. Raw unpeeled almonds variety Tuono (Prunus dulcis (Mill.) D. A. Webb) were irradiated using ⁶⁰Co source at dose of 0.5, 1.5, 3, 6, 8 and 10 kGy.     

Effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality changes of seer fish (Scomberomorus commerson) steaks stored in ice

The effect of reduced oxygen atmosphere and sodium acetate treatment on the microbial quality of seer fish (Scomberomorus commerson) steaks was determined during chilled storage (1–2 °C). The O₂ absorber reduced the oxygen content in the pack to less than 0.01% corresponding to 99.96% reduction within 24 h. The use of O₂ absorber with sodium acetate dip treatment (2% w/v) extended the sensory shelf life up to 25 days compared to only 12 days for control air packs and 20 days for untreated samples with O₂ absorber. A prominent lag phase was observed for many bacterium studied, particularly for the sodium acetate treated samples with O₂ absorber. On the day of sensory rejection, both the total mesophilic and psychrotrophic counts reached 7.7–8.1 and 7.1–7.9 log cfu/g, respectively. The sodium acetate treatment and reduced O₂ atmosphere affected the type of major spoilers. In air packed samples, H₂S-producers predominated followed by Brochothrix thermosphacta, Pseudomonas spp., where as in the untreated samples with O₂ absorber, H₂S-producers predominated the microbial flora followed by Lactobacillus spp. For treated samples with O₂ absorber, B. thermosphacta formed the major micro-flora followed by Lactobacillus spp. The use of O₂ absorber inhibited the growth of Pseudomonas spp., and total Enterobacteriaceae.