Walnut Quality Research Articles

Effects of Natural and Inoculation Fermentation on the Antinutrient Composition of African Walnut Enriched with Carrot

The effects of fermentation on the antinutrient composition of African walnut enriched with carrot and without carrot were carried out in this study. The submerged natural fermentation of non- enriched and carrot enriched (walnut 70%; carrot 30%) African walnut was carried out and lasted for 5 days during which microorganisms were isolated and identified. Species of Lactobacillus and Bacillus that are most commonly used as probiotics in foods, drugs, and dietary supplements, which was isolated during the natural fermentation of African walnut, were then used singly and in consortium during inoculation fermentation. During the fermentation processes, the anti nutritional analysis was carried out on the fermented samples on a daily basis. Result revealed that the bacteria B. subtilis strain b17a and L. lactis SFL8 were the most predominant bacteria during the natural fermentation. Raw African walnut and carrot have tannin, saponins, Phytate and oxalate of 2.47± 0.10, 1.46 ± 0.10, 14.41 ± 0.10 , 3.29 ± .10 and 2.28 ± .08, 2.10 ± .10,11.50± .05, 0.37± .03 respectively. Raw walnut generally had a higher anti-nutrient composition than carrot except in saponins. Fermentation led to the reduction in antinutrient composition in the fermented sample. Natural fermented African walnut (NFW) and natural fermented African walnut enriched with carrot (NFWC) resulted in the highest reduction in antinutrient composition. NFW and NFWC had a reduction in tannin, saponins, Phytate and oxalate from (2.47±0.008b, 1.46±0.010a, 14.41±0.026d, 3.29±0.05c) to (0.98 ± 0.05a, 0.61±0.05a, 4.35±0.03a, 0.27±0.05a) and (0.91±0.005a, 0.45±0.005a, 3.61±0.03a, 0.17±0.005a) respectively. Inoculation fermentation in which a monoculture of L. lactis or B. subtillis was used as starter culture resulted in the least reduction in the antinutrient content. Carrot enrichment of fermented African walnut had a reducing effect on the antinutrient composition of African walnut as the fermentation enriched with carrot all had a reduced tannin, Phytate and oxalate composition compared to those that were not enriched. Hence, fermentation and enrichment with carrot can be employed in improving the nutritional quality of African walnut thereby helping in effectively utilising their potential as human food.

Influence of radio frequency treatment on in-shell walnut quality and Staphylococcus aureus ATCC 25923 survival

Radio frequency (RF) treatment is considered as a potential method for eliminating food-borne pathogens from low moisture foods. In this study, a treatment protocol for pasteurizing in-shell walnuts (with 15.01% w.b. of moisture) was developed using a 6 kW, 27.12 MHz RF oven with the objective of maintaining product quality. The uniformity of RF heating was improved by combining with hot air and also product mixing and holding during treatment. The optimized RF treatment protocol for in-shell walnuts involved pre-heating between an electrode gap of 16.0 cm, followed by drying for 40 min between an electrode gap of 19.0 cm, the process finished with forced air cooling of the walnuts in a single layer. This RF treatment produced in excess of a 4-log reduction of Staphylococcus aureus ATCC while differences in kernel color were not significant between control and RF treated walnuts during accelerated storage. Peroxide values of RF treated samples increased by more than 1 meq/kg during storage but showed no significant differences to controls while fatty acid values of both the control and RF treated samples were below 0.6% during storage. The moisture content and water activities of walnut shells and kernels of control and RF treated samples initially decreased and then tended to stabilize during accelerated storage. During storage the population of S. aureus ATCC 25923 in RF treated samples was gradually reduced to below the detection limit. Therefore, RF treatments could be considered as an effective method to control pathogens on in-shell walnuts.

Microbiological Quality and Shelf Life of Pickled African Walnut (Tetracarpidium conophorum) Preserved with Lactic and Citric Acids

Microbiological Quality and Shelf Life of Pickled African Walnut (Tetracarpidium conophorum) Preserved with Lactic and Citric Acids

Classification of different walnut varieties using low-field nuclear magnetic resonance technology and cluster analysis

To classify different walnut varieties based on water and oil content of walnut, and determine their storage conditions, the low-field nuclear magnetic resonance (LFNMR) technology was used to obtain the NMR transverse relaxation time (T2) of the samples based on the physical and chemical indicators of the walnut quality. The relationship between the relaxation time and phase state of the internal material of the sample was investigated, and the characteristic parameters of the NMR spectrum signals were statistically analyzed using cluster analysis to determine the different walnut varieties, and three different components, as well as their contents, were detected by a LFNMR spectrometer: firmly bound water, weakly bound water, and weakly bound oil. Test results indicated that the oil peak was dominant in the overall signal intensity compared to the water peaks, in which the firmly bound water phase contributed more to the overall water signal between the water peaks. Using the analytic hierarchy process of cluster analysis, 21 walnut samples were classified into three different classes, based on the characteristic parameters of the water-content and oil-content spectrum signals. The first class contains four walnut varieties characterized by least water and highest oil contents; the third class contains two walnut varieties, with the highest water content and least oil content; whereas, the second class contains 15 walnut varieties, with both water and oil contents at medium levels. The results showed that LFNMR led to a rapid detection of moisture and oil contents in walnuts, while cluster analysis classified different walnuts varieties based on these parameters. This study also provided the basis for optimizing the storage methods and storage conditions of walnuts. Keywords: low-field nuclear magnetic resonance technology, transverse relaxation time, walnut, cluster analysis, decay curves DOI: 10.25165/j.ijabe.20191206.5064 Citation: Song P, Gao H, Zhao B J, Zhang A G, Liu F. Classification of different walnut varieties using low-field nuclear magnetic resonance technology and cluster analysis. Int J Agric & Biol Eng, 2019; 12(6): 116–121.

Classification of different walnut varieties using low-field nuclear magnetic resonance technology and cluster analysis

To classify different walnut varieties based on water and oil content of walnut, and determine their storage conditions, the low-field nuclear magnetic resonance (LFNMR) technology was used to obtain the NMR transverse relaxation time (T2) of the samples based on the physical and chemical indicators of the walnut quality. The relationship between the relaxation time and phase state of the internal material of the sample was investigated, and the characteristic parameters of the NMR spectrum signals were statistically analyzed using cluster analysis to determine the different walnut varieties, and three different components, as well as their contents, were detected by a LFNMR spectrometer: firmly bound water, weakly bound water, and weakly bound oil. Test results indicated that the oil peak was dominant in the overall signal intensity compared to the water peaks, in which the firmly bound water phase contributed more to the overall water signal between the water peaks. Using the analytic hierarchy process of cluster analysis, 21 walnut samples were classified into three different classes, based on the characteristic parameters of the water-content and oil-content spectrum signals. The first class contains four walnut varieties characterized by least water and highest oil contents; the third class contains two walnut varieties, with the highest water content and least oil content; whereas, the second class contains 15 walnut varieties, with both water and oil contents at medium levels. The results showed that LFNMR led to a rapid detection of moisture and oil contents in walnuts, while cluster analysis classified different walnuts varieties based on these parameters. This study also provided the basis for optimizing the storage methods and storage conditions of walnuts. Keywords: low-field nuclear magnetic resonance technology, transverse relaxation time, walnut, cluster analysis, decay curves DOI: 10.25165/j.ijabe.20191206.5064 Citation: Song P, Gao H, Zhao B J, Zhang A G, Liu F. Classification of different walnut varieties using low-field nuclear magnetic resonance technology and cluster analysis. Int J Agric & Biol Eng, 2019; 12(6): 116–121.

Distribution, relationship, and risk assessment of toxic heavy metals in walnuts and growth soil

Walnut is one of the most popular nuts worldwide and contains various mineral nutrients. Little is known, however, about the relationship between toxic heavy metals in walnuts and growth soil. In this study, we investigated the distribution, relationship, and risk assessment of five toxic heavy metals-lead (Pb), arsenic (As), chromium (Cr), cadmium (Cd), and mercury (Hg)-in walnuts and growth soil in the main production areas of China. The results showed that the main heavy metal pollution in walnut and soil was Pb and Cd. Regionally, positive relationships existed between heavy metals and the pH and organic matter of soil. In addition, we observed a notable uptake effect between walnut and growth soil. In this study, we found a significant correlation (r= 0.786, P< 0.05) between the bioconcentration factors and the longitude of the sampling areas. The risks (total hazard quotients) of five heavy metals toward children and adults by dietary walnut consumption were 46.8 and 56.2%, respectively. The ability to identify toxic heavy metal pollution in walnuts and growth soil could be helpful to screen suitable planting sites to prevent and control heavy metal pollution and improve the quality and safety of walnut.

Preserving quality of fresh walnuts using plant extracts

Fresh walnut kernel is considered as a way of walnut consumption, particularly in Asia, even though its market is less commercial than the dried kernel. There is a little knowledge about the storage of this commodity. Postharvest treatments including plant extracts either of Thymus vulgaris (ET) or walnut green husk (EWGH) in four concentrations (25, 50, 75 and 100 mg/L) and distilled water (as control) were assayed to increase fresh walnut kernel's shelf life at ambient temperature in the aqueous environment. Compared with untreated walnuts, the content of saturated fatty acids and linolenic was almost constant. Oleic acid concentration did not change considerably during storage in treated samples, while it was decreased in untreated kernels. The level of linoleic acid also decreased except for samples treated with the three higher EWGH concentrations. All treatments delayed lipid peroxidation and increment of acid value (AV). In addition, total antioxidant activity (TAA) and total phenolics (TPs) losses were observed by advanced time. After 28 days, the greatest losses of TAA and TPs were observed in untreated kernels. These results illustrate that ET and EWGH have potential to maintain fresh walnut quality during storage at 25 °C in the aqueous environment for 28 d.

Walnut Industry in Jammu and Kashmir: A Geographical Analysis

Walnut occupies an important position in the horticulture industry of Jammu and Kashmir. It has the monopoly of producing excellent quality of walnuts contributing more than 90 per cent of Indian walnut production. The temperate climatic conditions favour its cultivation and offer Jammu and Kashmir an exceptional edge to super pass the other states in terms of walnuts. In this research paper, an attempt has been made to find out spatiotemporal analysis of walnut production and to estimate economic advantage of this dry fruit. It has been observed that all the districts of the state produce the walnut except the Jammu and Samba. Further, it has been found that Jammu division recorded 15.21 per cent of growth in the area and 267.92 per cent growth in production. The foreign exchange earnings at the same time recorded an overall change of-89.45 per cent there are several limitations which encompass the walnut industry. Therefore it is an urgent need to save this dry fruit by involving people across all sections and by putting in place the all supportive measures.

Comparative analyses of three dehydration methods on drying characteristics and oil quality of in-shell walnuts

ABSTRACTDeveloping an effective drying method for in-shell walnuts (Juglans regia L.) is a major postharvest processing concern in the nut industry. Three drying methods, including hot air drying (AD), vacuum drying (VD), and hot air-assisted radio frequency drying (ARFD), were experimentally compared and analyzed. The changes in lipid oxidation attributes, fatty acid composition, total antioxidant capacity (TAC), and total phenolic concentration (TPC) of walnuts were determined after dehydration and during storage. The results showed that the drying time required for in-shell walnuts using ARFD was the shortest (138 min), followed by VD (185 min) and AD required the longest time (300 min). Particularly, AD resulted in the highest lipid oxidation, followed by VD and ARFD. The walnuts treated by ARFD contained more unsaturated fatty acid than those treated by AD. Moreover, both the reduced power assay and free radical scavenging capacity tests showed that ARFD and VD had little effect on the TAC and TPC of walnuts during the drying process and storage. Overall, ARFD provides an effective and rapid drying method for in-shell walnuts.

Effects of Ethephon on Fresh In‐Husk Walnut Preservation and its Possible Relationship with Phenol Metabolism

Fresh walnuts (Juglans regia L.) are in demand due to their high nutrition value and unique flavor of the kernel. In this study the effects of ethephon on decay control and kernel quality of fresh walnuts and its possible relationship with phenolic metabolism were investigated. Fresh in-husk walnuts treated with 0, 10, 500, and 800 mg/L ethephon were stored at 0 ± 0.5°C for 42 d. Decay incidence, total phenolic (TP) compounds, phenylalanine ammonialyase (PAL), polyphenol-oxidase (PPO), and peroxidase (POD) activities of green husks, and acid values (AV) and peroxide values (PV) of kernels were assessed at 6-d intervals. The respiration rate of the whole walnut was assessed at 3-d intervals. Treatment with 500 mg/L ethephon enhanced respiration, reduced the decay index, and inhibited PPO and POD activity and browning of green husks, and also promoted PAL activity and TP content of green husks. This treatment also reduced the PV and AV of kernels. A concentration of 10 mg/L ethephonhad similar, but weaker, effects on walnuts. Treatment with 8000 mg/L ethephon, however, had opposite effects. These data indicate ethephon treatment at a proper concentration can extend storage life and maintain kernel quality of fresh in-husk walnuts through the manipulation of phenolic metabolism.

Establishing quality parameters for Australian walnuts

Australian walnuts are perceived to be of high quality; however, there has been no systematic process to describe walnut quality in Australia. A set of standard parameters could provide credible evidence for any claim of 'superior quality', as well as increasing the value of the industry by producing more nuts of the desired quality. A first step in the production of high quality walnuts is to develop a better understanding of what 'quality' represents and how that quality can be achieved. A project involving six walnut producers selected from different growing regions of Australia, aimed to identify factors that may influence walnut quality. Nuts were assessed at harvest for physical attributes (size, weight, kernel colour, shell and kernel defects) and at harvest and various times during postharvest storage for hedonistic qualities (texture, taste, rancidity, aftertaste). Tests for free fatty acids and peroxide value were conducted independently and approximately 3, 6 and 9 months after harvest. All peroxide values were below 2 and all free fatty acid values below or close to 0.2 indicating that the initial high quality had not deteriorated. Storage up to 6 months appears to have no adverse effect on walnut quality if the nuts remain in-shell. Some decline in walnut quality was evident by 9 months, suggesting that storage beyond that period may become an issue. Participants now have some baseline information for developing benchmarks for Australian walnut quality and a basis from which to further develop and establish walnut quality parameters.

Evaluation of Some Pollinizers and Their Suitability on Productivity and Quality of Walnut (Juglans regia) Cultivars

The present study was carried out at Horticultural Farm, Division of Fruit Science, SKUAST, Shalimar, Srinagar (Kashmir) during 2012–13 to evaluate various walnut pollinizers in improving the productivity and nut quality. Pollen germination and its viability, pollen production rate, anther and pollen morphology of ‘SKAU-W-0020’ and ‘SKUA-W-0022’ and influence of pollination method i.e. open and cross on nut and kernel characteristics was studied. Highest pollen viability (91.4%) was observed in selection ‘SKAU-W-0020’. Maximum pollen germination (51.5%) was observed in ‘SKAU-W-0020’ on medium containing agar agar powder (1%) + sucrose (15%) + boric acid (100 ppm) + CaCl2 (1 mM). Pollen production varied significantly within genotypes with maximum (1, 43, 75000) in ‘SKAU-W-0020’ and minimum (1, 20, 60000) in ‘SKAU-W0022’. Maximum anther length (2457 μm) and width (1228 μm) was in ‘SKAU-W-0020’; however, maximum pollen length (35 μm) and width (39.6 μm) was in ‘SKAU-W-0022’. Nut weight, diameter, length and kernel length, weight and kernel percentage in ‘SKAU-W-0025’ and ‘SKAU-W0015’ increased through cross pollination, however in ‘SKAU-W-0024’ and ‘SKAU-W-0008’ reverse trend was observed.

Export Performance of Indian Walnut: Decomposition Analysis and Gravity Model Approach

Export performance of Indian walnut has been comprehensively analyzed in this study employing chronological data. The export of walnut from India has significantly increased over the years, but still constituted only 3 per cent of total world export. Between 1979 and 2012, the export of shelled walnut has significantly increased, at an annual growth rate of about 3 per cent, while walnut with shell has shown a declining trend over the years, implying widening of markets for value-added products of walnut. The export instability in quantity and value of both shelled and walnut with shell has declined over the years; however, the instability in unit price of shelled walnut has increased over the years. The decomposition analysis has revealed highest contribution of change in mean export quantity among the other components of change in the average export value of walnut. The unit value of Indian walnut export has been found lower compared to many other nations, indicating the possibility of a higher price by ensuring quality parameters as per global standards. The estimates of gravity model have revealed that per capita GDP, agricultural GDP, and consumption of importing partners, and also the Indian GDP are the significant factors determining Indian walnut export. The study has also unveiled unexploited potential of Indian walnut export to some trading partners. The study has emphasized on the improvement in quality of walnut, integration of production and value addition, export promotion and strengthening of bilateral ties with regular trade partners for enhancing export of Indian walnut.

기후변화 영향에 따른 호두나무 재배지역 변화 예측

본 연구에서는 호두나무에 대하여 단기임산물 재배적 지도를 바탕으로 기후변화를 고려한 전국의 재배가능지역을 MaxEnt 모델을 이용하여 추출하였다. RCP 4.5 및 8.5 시나리오와 HadGEM2-AO모델을 이용하여 2050년대와 2070년대의 기후변화에 따른 재배지역 변화를 예측하였다. 분석결과, 미래의 재배적지면적을 현재 수치와 비교하였을 때, RCP 4.5에서는 충청남도, 전라북도, 전라남도에 이르는 우리나라 서쪽 지역이 주로 감소할 것으로 나타났으며, RCP 8.5에서는 경상북도, 경상남도 일부 지역을 중심으로 감소할 것으로 나타났다. 하지만, 평균고도가 600m 이상으로 높은 지역인 강원도는 2070년대 RCP 4.5에서 18.3%, RCP 8.5에서 56.6%가 증가할 것으로 나타나 기후변화의 영향 정도에 따라 전국적으로 재배가능지역의 차이가 있는 것으로 나타났다. 현재 호두 생산량이 가장 많은 지역을 분석한 결과 공주시, 김천시, 영동군은 2070년대에는 RCP 8.5에서 재배지역의 감소가 클 것으로 예상되었으며, 공주시는 RCP 4.5에서 감소폭이 더 큰 것으로 나타났다. 무주군과 천안시는 현재의 재배가능지역이 모든 시나리오에서 유지될 것으로 나타났다. 본 연구의 결과는 미래 기후변화에 따른 영향이 불가피한 상황에서 예상되는 피해를 최소화하고 경쟁력 있는 임산물 생산을 위한 기후변화 영향평가 자료로 활용될 것으로 판단된다. The objective of our study was to predict future cultivation areas for walnut trees (Juglans sinensis), using the cultivation suitability map provided from Korea Forest Service and MaxEnt modelling under future climate conditions. The climate conditions in 2050s and 2070s were computed using the Regional Climate Prediction (RCP) 4.5 and 8.5 scenarios with the HadGEM2-AO model. As a result, compared to the present area, the cultivation area of the western Korea including Chungcheongnamdo, Jeollabuk-do, Jeollanam-do decreased on a national scale under RCP 4.5, and those of Gyeongsangbukdo and part of Gyeongsangnam-do decreased under RCP 8.5. However, Gangwon-do which is located in higher altitude over 600 meters than other regions showed increases in cultivation areas of 18.3% under RCP 4.5 and of 56.6% under RCP 8.5 by 2070s. The predicted map showed large regional variations in the cultivation areas with climate change. From the analysis of current top ranking areas, the cultivation areas in Gimcheon-si and Yeongdong-gun dramatically decreased by 2070s under RCP 4.5 and 8.5; that of Gongju-si decreased more under RCP 4.5; and those of Muju-gun and Cheonan-si sustained the areas by 2070s under both scenarios. The results from this study can be helpful for providing a guide for minimizing the loss of walnut production and proactively improving productivity and quality of walnuts with regard to unavoidable climate change in South Korea.

Properties of walnut influenced by short time microwave treatment for disinfestation of insect infestation

Insect infestation is the major cause of losses in many stored products such as grains, seeds, cereals and nuts. The use of chemicals to control insect infestation has widely been adopted but now is a cause of concern because of hazardous side effects. Alternative quarantine methods such as ionizing radiation, controlled atmosphere, conventional hot air treatment and dielectric heating have been suggested. Recent studies have indicated that microwave treatment is a potential means of replacing other techniques because of selective heating, absence of pollution in the environment, the achieving of equivalent or better quality retention and energy minimization. However improper application of microwaves can cause irreversible changes in the quality of the final product. The main objective of this research is to evaluate the effect of microwave power level and exposure time on the quality of walnuts. The quality parameters studied were water activity, colour change, temperature rise, peroxide value (PV) and free fatty acid levels (FFA). It was found that microwave power level and exposure time significantly affected colour change and temperature rise. Untreated walnut kernels exhibited significantly higher (p < 0.05) peroxide and FFA values than treated walnut kernels. Microwave treatment to target temperatures of 50–55 °C (which is unfavourable for insect survival) made the PV of walnut drop down to between 1.35 and 1.42 meqO2/Kg (from the initial value of 2.89 ± 0.048) and FFA value to 0.63–0.69% (from 1.08 ± 0.037).

THE EVALUATION OF STRAW PIT IRRIGATION METHOD IN WALNUT ORCHARD IN LOESS PLATEAU AREA

The rainfall in Loess Plateau Area is normally between 350-450 mm, the drought is the main limiting factor to influence the yield and the quality of walnut. The research, through the analysis of costs and the economic benefit of straw pit irrigation method (plastics film covering), flooding irrigation, drip irrigation, sprinkling irrigation. The method of irrigation in vertical pit (with the straw in, plastics film covering) is the best. The method cannot only collect the rain in the rain season of July, August, September, and use it in drought season of March, April, May, but also suit the situation in Loess Plateau Area with relatively less land, more labor force, and drought climate, which is very different from developed countries.

LOSS OF KERNEL QUALITY ASSOCIATED WITH HARVEST DELAYS IN TASMANIA, AUSTRALIA

Knowledge of factors that adversely affect the quality of walnuts grown in Tasmania, Australia, is limited. Experiments over two years investigated the temporal development of fruit maturity and the effect of harvest delays on kernel quality. The progression of kernel maturity, or packing tissue brown (PTB), was similar in ‘Lara’ and ‘Vina’, with 95% PTB predicted between 77 and 87 days after January 1. The onset of harvest, defined as 80% hullable fruits, was similar for the two cultivars, occurring within 5-days of each other. Delaying harvest beyond 95% PTB reduced kernel quality in both years. In 2009-10, delaying harvest significantly reduced the percentage of extra-light kernels for ‘Vina’, ‘Howard’ and ‘Chandler’ i.e., for ‘Chandler’, from 77% extra-light with no harvest delay compared to 63% a 7-day harvest delay. Delaying harvest by 7 days significantly increased the percent of kernels with yellow pellicle i.e., from less than 6% yellow pellicle with no delay to 24, 28 and 51% of ‘Howard’, ‘Vina’ and ‘Chandler’ nuts, respectively, with a 7-day harvest delay. Similarly, in 2011-12 ‘Lara’ and ‘Chandler’ nuts harvested 8 days or more after tree shaking had fewer extra-light kernels, and more yellow pellicle and mould, compared to nuts harvested earlier. Additional research will identify seasonal variations and improve the initial description of fruit maturity and factors affecting kernel quality.

Thermal treatment and storage condition effects on walnut paste quality associated with enzyme inactivation

In this study, walnut paste was heated at 60, 75, and 90 °C with three selected times for enzyme inactivation, and its quality stability was determined under accelerated storage conditions by evaluating peroxide value (PV), conjugated diene value (CDV), fatty acid value (FFA) and fatty acid composition. The results showed that the mean PV, CDV and FFA values of the heated paste samples increased with increasing treatment temperature and time. The PV and CDV were reduced or stable, while the FFA values increased significantly during storage period. However, no significant quality difference was observed between controls and heated walnut paste samples with vacuum package after accelerated storage for 20 days. Compared with unheated walnut kernels and cold-pressed oils in vacuum or normal package under same storage conditions, the mean PV of the unheated paste were the lowest, while its mean FFA values were the highest. FFA values of the paste were still lower than the acceptable range (FFA < 0.6%) used by industry for good walnut quality, suggesting that vacuum or normal packages can be used to keep quality of walnut paste for 20 days at 35 °C simulating 2 years of storage at 4 °C or 2 months at 25 °C.

Analysis of UK walnut market import purchase behaviour

Purpose – This paper aims to use readily available data to validate several predictions on UK walnut import and consumer use behaviours. It then seeks to hypothesise how this information can be used to determine whether and how additional value can be created in the chain. Design/methodology/approach – The chain used was that from sourcing to retail sale of walnuts in the UK. The data used were: UK import price/quantity/origin and total consumption data, global comparisons for import price/quantity/origin and total consumption data. Findings – This paper validates predictions for walnut quality, market size and pricing from a simple model for the UK walnut market. The UK walnut market is small (0.26 g/capita/day) but expanding per capita (8 per cent pa). Import prices are low (15-25 per cent below several other major EU importers) but rising in real terms (7 per cent pa). The UK generally sources walnuts opportunistically from low cost low “international standard” quality suppliers. These findings are consistent with model predictions of market behaviour and previous findings on walnut quality. Practical implications – There may be an opportunity to improve quality specifications for the UK walnut market &amp;/or to expand the UK market into higher quality uses. Both options require educating the UK consumer market in the additional consumer value created. Originality/value – The study indicates the extent of price seeking purchasing behaviour within global markets for an agricultural product (walnuts). It shows this is not a globally consistent market response and thus offers opportunities for all participants in the UK walnut retail value chain to provide enhanced consumer value.

Effect of 60Coγ-irradiation doses on nutrients and sensory quality of fresh walnuts during storage

Fresh Liaohe walnuts (Juglans regia cv. Liaoning4) were given 60Coγ-irradiation doses of 0, 0.1, 0.5, 1.0 and 5.0kGy and stored at 0±1°C for 120d. The concentrations of fat, protein, fatty acid, soluble sugar, water and vitamin E (VE), peroxide value (PV) and the sensory quality were determined at regular intervals during storage. Irradiation at 0.1, 1.0 and 5.0kGy accelerated lipid oxidation, increased the PV, and decreased the sensory quality and VE content of walnuts during storage. However, an irradiation dose of 0.5kGy resulted in less oxidative degradation, reduced PV, and maintained a higher VE concentration and better sensory quality of walnuts during the 90d storage. We conclude that a dose of 0.5kGy is the optimal dose for the preservation of fresh walnuts over a 90d storage period.