Effect of γ-irradiation on the physicochemical and sensory properties of cashew nuts (Anacardium occidentale L.)

The present study evaluated cashew nuts' quality as a function of γ-irradiation dose in order to determine dose levels causing minimal undesirable changes to the product. Physicochemical (colour, peroxide value, hexanal content, fatty acid composition, volatile compounds) and sensory (colour, texture, odor, taste) properties of cashew nuts were determined after irradiation at doses up to 7 kGy. Results showed a five-fold increase in peroxide value (PV) and a two-fold increase in hexanal content after irradiation at a dose of 7 kGy. Of the fatty acids determined, stearic acid concentration increased while oleic acid decreased with irradiation dose. PUFA were unaffected by irradiation. Volatile compounds such as aldehydes, ketones and alcohols increased after irradiation indicating enhanced lipid oxidation. Colour parameter a∗ increased (p < 0.05) at doses >3 kGy while colour parameters L∗ and b∗ remained unaffected by irradiation. Sensory analysis showed that cashew nuts remained organoleptically acceptable at doses <3 kGy.     

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     

Effect of γ-irradiation on the physicochemical and sensory properties of walnuts (<Emphasis Type="Italic">Juglans regia</Emphasis> L.)

The present study evaluated physicochemical and sensory quality parameters of walnuts as a function of irradiation dose in order to determine dose levels causing minimal undesirable changes to walnuts. Physicochemical parameters including peroxide value (PV), hexanal content, fatty acid composition, volatile compounds and sensory parameters including color, texture, odor and taste were determined for unirradiated and irradiated walnuts at radiation doses of 1.0, 1.5, 3.0, 5.0 and 7.0 kGy. PV increased from 1.1 to 3.0 meq O₂/kg walnut oil while the hexanal content increased from 3.80 to 34.3 mg/kg walnut after irradiation at a dose of 7.0 kGy. Of the fatty acids determined, stearic and palmitic acids concentration increased while oleic acid decreased with irradiation dose. Polyunsaturated fatty acids were unaffected by irradiation. Volatile compounds such as aldehydes, ketones, alcohols and hydrocarbons increased after irradiation indicating enhanced lipid oxidation. Color parameter L*, a* and b* remained unaffected by irradiation. Sensory analysis showed that taste was the most sensitive of all sensory attributes for the evaluation of walnut quality. Based on taste and odor scores, walnuts remained organoleptically acceptable at doses ≤3.0 kGy.     

Effect of γ-irradiation on the physicochemical and sensory properties of raw unpeeled almond kernels (Prunus dulcis)

The present study evaluated the quality of raw unpeeled almonds as a function of irradiation dose in order to determine dose levels causing minimal undesirable changes to almonds. Physicochemical (color, peroxide value, hexanal content, fatty acid composition, volatile compounds) and sensory (color, texture, odor, taste) properties of almonds were determined as a function of irradiation dose.Results showed a ten-fold increase in peroxide value (PV) after irradiation at a dose of 7 kGy. A small but statistically significant (p < 0.05) change was observed in hexanal concentration as a result of irradiation. No statistically significant (p > 0.05) changes were recorded in polyunsaturated fatty acids (PUFA) up to a dose of 7 kGy while monounsaturated fatty acids (MUFA) decreased manifested as a respective increase in saturated fatty acids (SFA) up to 3 kGy. Volatile compounds such as aldehydes, ketones and alcohols increased with increasing irradiation dose indicating enhanced lipid oxidation. Color parameter L^? decreased (p < 0.05) at doses > 3 kGy while color parameters a^? and b^? remained unaffected by irradiation. Sensory analysis showed that almonds remained organoleptically acceptable up to a dose of 3 kGy.Industrial Relevance: Irradiation is very efficient in controlling insects and growth of aflatogenic Aspergillus spp. in dry nuts.     

Effects of low dose gamma irradiation on microbial inactivation and physicochemical properties of fried shrimp (Penaeus vannamei)

Changes in microbiological, physicochemical and sensory properties of shrimp gamma irradiated with ⁶⁰Co at doses of 0, 1, 3, 6, 9 kGy were investigated. Irradiation at 6 kGy eliminated most of the spoilage microorganisms and did not affect sensory quality. The L* value increased as irradiation dose increased, while a* value decreased as irradiation dose increased. Irradiation had no significant effect on the texture of shrimp samples; however, increasing the dose up to 9 kGy significantly increased the amount of volatile compounds, such as, alcohols, ketones, aldehydes, furans, and oxides. According to the total sensory points, the appearance and flavour of the shrimp product was considered as acceptable by sensory evaluation when irradiated at doses of 0–6 kGy. These results showed that gamma irradiation processing (<6 kGy) had the potential to extend the shelf life of fried shrimp.     

E‐Beam Irradiation for Improving the Microbiological Quality of Smoked Duck Meat with Minimum Effects on Physicochemical Properties During Storage

This study was performed to evaluate the effect of different doses (0, 1.5, 3, and 4.5 kGy) of e‐beam irradiation on the quality parameters (pH, Hunter's parameter, and heme pigment) and stability qualifiers (peroxide value [POV], thiobarbituric acid reactive substances [ TBARSs], and total volatile basic nitrogen [TVBN]) of smoked duck meat during 40 d of storage under vacuum packaging at 4 °C. The initial populations of total bacteria (7.81 log CFU/g) and coliforms (5.68 log CFU/g) were reduced by approximately 2 to 5 log cycles with respect to irradiation doses. The results showed that pH, myoglobin, met‐myoglobin, L^*, a^*, and b^* showed significant differences with respect to different doses and storage intervals; a^* and b^* did not vary significantly because of storage. Higher pH was found in samples treated with 4.5 kGy at 40 d, while the minimum was observed in nonirradiated samples at day 0 of storage. Higher POV (2.31 ± 0.03 meq peroxide/kg) and TBARS (5.24 ± 0.03 mg MDA/kg) values were found in 4.5 kGy‐treated smoked meat at 40 d and the lowest was reported in 0 kGy‐treated meat at initiation of storage (0 d). However, irradiation suppressed TVBN during storage and higher TVBN (7.09 ± 0.32 mg/100 mL) was found in duck meat treated with 0 kGy at 40 d. The electronic nose (e‐nose) effectively distinguished flavor profiles during the different storage intervals. The results showed that different sensory attributes did not vary significantly with respect to the dose of irradiation. We conclude that low dose of e‐beam irradiation and vacuum packaging is beneficial for safety and shelf life extension without affecting the sensory characteristics of smoked duck meat.     

Moisture Dependent Geometric and Mechanical Properties of Wild Pistachio (Pistacia vera L.) Nut and Kernel

In this research, wild pistachio (Pistacia vera L.) nuts and kernels were analyzed for selected geometric properties and mechanical behavior under compression loading. The average length, width and thickness arithmetic and geometric mean diameter of wild pistachio nuts at 5.83% w.b. were 13.98, 8.76, 7.25, 9.93, and 9.75 mm, while the corresponding values of kernels at 6.03% w.b. moisture content were 11.07, 5.92, 4.83, 7.21, and 6.88 mm, respectively. As the moisture content of pistachio nut increased from 5.83 to 30.73% w.b., the bulk density, apparent density and terminal velocity were found to increase from 521 to 543 kgm^?3, 809 to 829 kgm^?3, and 5.51 to 6.29 ms^?1, respectively, whereas porosity decreased from 35.14% to 34.63%. The results revealed that wild pistachio nut required higher rupture force and energy to crack wild pistachio nuts for compression along the L-axis as compared to other two axes.     

Volatile composition and sensory quality of Spanish pomegranates (Punica granatum L.)

BACKGROUND: Pomegranate is highly valued for its health‐promoting effects. Fruits of nine pomegranate cultivars were analysed for volatile compounds, antioxidant activity and quality parameters, including maturity index and CIEL*a*b* colour. Volatile compounds were isolated from fresh juices using hydrodistillation; extracts were analysed using gas chromatography/mass spectrometry. Fruit colour was influenced by cultivar and grouping of cultivars according to their taste (sweet, sour‐sweet or sour), with sweet fruits having more intense red colour and higher lightness values. RESULTS: A total of 18 compounds were found in pomegranate aroma profiles, including monoterpenes, aldehydes, alcohols, monoterpenoids and linear hydrocarbons. The most abundant compound were trans‐2‐hexenal, 3‐carene, α‐terpinene and α‐terpineol. The total concentration of volatiles ranged from 1.7 to 10.9 g kg^?1. Overall consumer liking of pomegranate juices was associated with the presence of monoterpenes such as α‐pinene, β‐pinene, β‐myrcene, limonene and γ‐terpinene. The presence of aldehydes such as hexanol, hexanal and cis‐3‐hexenol was correlated with poor overall consumer liking. CONCLUSION: Fruits from the cultivar Mollar de Elche 2 were those most suited for juice processing because they had the highest total concentration of volatiles, which was related to high overall consumer liking, intense and acceptable fresh pomegranate odour and flavour (high scores of satisfaction degree), medium intensity of red colour and low sourness. Copyright © 2010 Society of Chemical Industry     

Effect of gamma irradiation and frozen storage on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet

The present study was conducted to evaluate the combined effect of low‐dose gamma irradiation (1, 3 and 5 kGy) and frozen storage (5 months at ?20 °C) on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet. Our statistical analysis showed that irradiation process and frozen storage time had a significant effect (P < 0.05) on total volatile nitrogen (TVN), peroxide value (PV), thiobarbituric acid (TBA) and pH. The level of all of these factors increased with increasing frozen storage time. At the end of the fifth month of frozen storage, the lowest and the highest level of TVN, PV and TBA were corresponding to the irradiated samples at 3 and 5 kGy, respectively. In terms of the overall acceptability of their texture, odour, colour and taste, irradiated samples at 3 kGy had the best quality and remained acceptable after 5 months frozen storage. The optimum dose of gamma radiation of rainbow trout fillets according to chemical and sensory analysis was obtained at 3 kGy.     

电子束辐照对松花粉脂质氧化及其品质的影响

以原松花粉为试材,研究电子束辐照对其杀菌效果、脂肪酶活力、脂质氧化性能和营养品质的影响,并分析了破壁松花粉在加速氧化过程中色泽、过氧化值和挥发性成分的变化。结果表明,电子束辐照可显著降低松花粉中微生物含量,且辐照剂量越大,杀菌效果越显著;菌落总数、霉菌酵母数和大肠菌群的D10值分别为2.20、1.95和1.84 kGy;随着辐照剂量的增加,松花粉中脂肪酶活力、类胡萝卜素含量和游离脂肪酸含量显著降低,过氧化值略有升高但总体仍处于较低水平,当辐照剂量为8 kGy时,脂肪酶灭活率为53.52%,类胡萝卜素保留率为60.81%,游离脂肪酸含量为1.38 mg/kg,过氧化值为0.46 meq/kg;此外,8 kGy剂量辐照对松花粉的基本营养成分及氨基酸含量无明显影响,在加速氧化过程中,破壁松花粉的色泽无明显变化,过氧化值、己醛和己酸含量增幅不大。表明8 kGy电子束辐照对松花粉营养品质影响不大,并能有效杀灭微生物,抑制脂质氧化,提高产品储藏稳定性。     

Effects of gamma irradiation dose and short-term storage on phytochemicals,antioxidants, and textural properties of boiled ‘Tainan 9’ peanuts

Boiled peanuts are preferable as a ready-to-eat healthy snack; however, gamma irradiation as a postharvest treatment of raw peanuts may induce unfavourable food components. Hence, the phytochemical, antioxidant, and the texture of boiled ‘Tainan 9’ peanuts pretreated with gamma irradiation (0, 2.5, 5, and 10 kGy) and stored at 29 ± 2 °C for up to 180 days were investigated. Both gamma irradiation and storage time contributed to testa darkening in raw peanuts. In boiled irradiated products, irradiation doses and storage time affected the moisture content (MC), total proteins, total oil, total soluble sugars, and antioxidant capacity (P ≤ 0.05). Total phenolic and flavonoid contents showed an increase at days 90 and decreased at days 180 across all treatments. A positive correlation was observed among ferric reducing antioxidant power (FRAP), total phenolics, and total flavonoids. Gamma irradiation at 10 kGy led to increase of peroxide value (PV) (P ≤ 0.05), but malondialdehyde (MDA) content was unaffected. Textural properties of boiled irradiated peanuts were soft. As a result, gamma irradiation at 5 kGy is recommended for postharvest treatment of raw peanuts with subsequent storage up to 180 days to obtain the eating quality of boiled peanuts with good phytochemicals and antioxidant properties, which is a challenge for food industry.     

Development of Pistachio (Pistacia vera L.) Spread

Pistachio nut (Pistacia vera L.) is one of the most delicious and nutritious nuts in the world. Pistachio spreads were developed using pistachio paste as the main component, icing sugar, soy protein isolate (SPI), and red palm oil (RPO), at different ratios. The highest mean scores of all the sensory attributes were depicted by spreads that were made without addition of SPI. It was found that the work of shear was 0 to 11.0 kg s for an acceptable spread. Sensory spreadability, overall texture, spreadability, and overall acceptability were negatively correlated (R > 0.83) with the work of shear of spreads. The findings indicated that the presence of RPO had a direct effect on the viscoelastic behavior of the pistachio spreads. The a values, which are related to the green color of the pistachio product ranged from 1.7 to 3.9 for spread without addition of RPO, and 4.0 to 5.3 in the presence of RPO. Practical Application The development of pistachio spread would potentially increase the food uses of pistachio and introduce consumers with a healthier snack food.     

Characterisation of three starch degrading enzymes: thermostable β-amylase, maltotetraogenic and maltogenic α-amylases

White sesame seeds (Sesamum indicum L.) were studied with the purpose to evaluate γ-irradiation effect at 2.5, 5.0 and 10.0 kGy on lipid and fatty acid content, colour and protein allergenicity and to identify whether sesame oil was extracted from irradiated seeds by using High Resolution Nuclear Magnetic Resonance spectroscopy (HR-NMR). The fat decreased significantly, whereas triglyceride and phospholipid content was significantly decreased by the increase of irradiation dose. Monounsaturated and polyunsaturated fatty acids and unsaturated/saturated fatty acids ratio decreased. The presence of radiolytic decomposition products, shown by NMR, formed after a 2.5 kGy dose, confirmed that the lipid content decrease was a result of the irradiation process. The allergenicity of storage seed proteins was not significantly affected by irradiation up to 10.0 kGy. Colour parameter a^* increased after 5.0 kGy, while L^* values decreased significantly after 2.5 kGy. Conclusively, irradiation could be applied at doses <2.5 kGy while sustaining the sesame seed nutritional benefits.     

Effect of gamma irradiation on fungal load, chemical and sensory characteristics of walnuts (Juglans regia L.)

Walnuts of the Baladi variety were treated with 0, 0.5, 1.0, 1.5 and 2.0 kGy of gamma irradiation. The irradiated and unirradiated nuts were stored at room temperature (15-18°C) and 50-70% r.h. Fungal load, proximate composition (moisture, protein, fat and ash contents), chemical changes and sensory properties of nuts were evaluated immediately after irradiation and after 12 months of storage. The results indicated that gamma irradiation reduced fungal load. The doses applied did not cause any significant change in proximate composition of walnuts. Gamma irradiation increased total acidity and decreased iodide value and volatile basic nitrogen (VBN) immediately after treatment. After 12 months of storage, gamma irradiation decreased total acidity and peroxide value and increased iodide value and VBN. No significant differences were observed between irradiated and nonirradiated samples in flavor and aroma immediately after irradiation. After 12 months of storage, higher doses (1.5 and 2.0 kGy) had a negative effect on sensory characteristics.     

Gamma radiation effect on quality changes in vacuum‐packed squid (Illex argentinus) mantle rings during refrigerated (4–5 °C) storage

The effect of gamma radiation (0, 1.8, 3.3 and 5.8 kGy) on microbiological, chemical and colour characteristics of vacuum‐packed squid (Illex argentinus) mantle rings was studied. Total viable counts; psychrotrophic bacteria counts, Escherichia Coli, Staphylococcus aureus and Clostridium perfringens; total volatile basic nitrogen (TVBN) and colour difference were analysed during 29 days of storage at 4–5 °C. Higher doses of gamma radiation significantly reduced Total Viable, phychrotrophic counts and TVBN production (P < 0.05) in a dose‐dependent way, delaying squid spoilage. Colour difference of non‐irradiated samples with respect to first day significantly increased while it was constant in radiated samples during 22 days (P < 0.05). Independently from the dose, radiation avoided colour changes of squid rings. Gamma irradiation was effective in delaying deterioration reactions, improving microbiological, chemical and colour quality of vacuum‐packed squid rings stored at 4–5 °C.     

The irradiation of spices, packaging materials and luncheon meat to improve the storage life of the end products

Spices and packaging materials were exposed to γ‐irradiation at a dose of 10 kGy. Luncheon meat was prepared with irradiated or non‐irradiated spices and packaged in irradiated or non‐irradiated packaging materials. Packaged luncheon meat was treated with 2 kGy. Irradiated and non‐irradiated packaged luncheon meat were kept in a refrigerator (1–4 °C) for 12 months. Microbiological, nutritive and chemical characteristics of luncheon were evaluated after processing and during storage; whereas, sensory quality was evaluated only after irradiation. γ‐Irradiation decreased the microbiological counts of spices, packaging materials and packed products and increased its shelf‐life. No significant differences in moisture, protein, fat, pH value, total acidity, lipid peroxide and volatile basic nitrogen were observed as a result of irradiation. Sensory evaluation showed that all the combinations of treated luncheon meats were acceptable. However, the taste, odour, appearance and texture scores of irradiated packaged products were significantly lower than those of non‐irradiated samples.     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) seeds: effect on colour,cooking quality and pasting characteristics

Cowpea seeds were treated to various gamma irradiation doses, and their colour, cooking quality and pasting properties studied. Irradiation at 50 kGy resulted in significant browning (indicated by decreases in L colour value) of cowpea seeds. At 2 and 10 (but not at 50) kGy, irradiation led to significant reduction in cooking time of cowpea seeds possibly through irradiation‐induced degradation of starch and pectic substances (indicated by decreases in peak and final viscosities) leading possibly to enhanced heat and mass transfer within the seed cotyledon and cell wall, respectively. At 50 kGy, the cooking time of cowpea seeds was prolonged significantly owing possibly to extensive polymer cross‐linking occurring within the seeds at this high dose. Splitting of cowpea cotyledons during cooking decreased significantly at 50 kGy, but was unaffected at 2 and 10 kGy. Irradiation resulted in significant leaching of nutrients from cowpea seeds during cooking in a dose‐dependent manner.     

Changes of colour and pH in fish musculature after ionizing radiation exposure

Irradiation of meat causes sensory changes as do other technological methods. The most significant sensory and quality indicator of meat is colour; therefore, the effect of irradiated pieces of fish was studied in relation to colour changes. Colour was measured at the musculature of Oncorhynchus mykiss. The parameters of colour, L*, a* and b*, were determined with the portable Superchroma S-Spex (Braive) spectrophotometer in the CIELAB system before irradiation (3 h post mortem) and after irradiation (⁶⁰Co source, a dose of 3 kGy and a dose rate of 3.33 kGy h^–1) (5 h post mortem). The change of L* was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh. a* was identical and b* decreased. This effect differs from that of irradiated pork. The decrease of the pH was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh.     

Influence of gamma irradiation on growth and survival of Escherichia coli O157:H7 and quality of cig kofte, a traditional raw meat product

Cig kofte is a traditional Turkish food containing raw ground meat. Samples inoculated with Escherichia coli O157:H7 were irradiated at 0.5–6 kGy with a ⁶⁰Co source and stored at 4 and 25 °C. Total aerobic mesophilic count decreased with increasing irradiation doses, D₁₀ value was 0.83 kGy. Escherichia coli O157:H7 count decreased from 5.1 log₁₀ CFU g^?1 to an undetectable level (<1 log₁₀ CFU g^?1) after 1‐day storage at 4 °C following irradiation at 2 kGy, D₁₀‐value was 0.29 kGy. Irradiation doses up to 2 kGy did not affect sensory quality after 1 day. There was colour loss in samples irradiated at 2 kGy or above and stored for longer periods. Storage of the irradiated products at abused temperature must be avoided for safety assurance. Irradiation at 2 kGy has a great potential for extending the shelf‐life of cig kofte and assuring safety by decreasing the number of E. coli O157:H7 and other bacteria, but further studies with suitable package designs are needed to decrease quality degradation during extended storage.