Physicochemical characterisation and in vitro Starch digestion of Avocado Seed Flour (Persea americana V. Hass) and its starch and fibrous fractions

The avocado seed is considered a by-product of their pulp exploitation and today it does not present relevant food or industrial applications. In this study, we evaluate the potential use of its flour, their isolated starch and fibre fractions. After processing, the flour yielded 46.28%, and showed 6.7% of protein and low fat and ash contents (3.4, and 2.71% respectively). The starch yielded 27.28% with low-fibre content that influenced its viscosity properties; as well as their water absorption index (WAI), water solubility index (WSI) and oil absorption index (OAI), that were 2.43%, 11.22% and 0.16% respectively. The in vitro starch digestion of the different obtained fractions showed higher amounts of rapidly digestible starch (56.8%–75.36%, flour and starch respectively). The functional properties of the materials were correlated with strong molecular interactions with their apparently unique amylose structure; for this, this by-product may have different potential for food applications.     

The physicochemical and binder properties of starch from Persea americana Miller (Lauraceae)

Avocado starch was extracted from the kernels of the fruit Persea americana Miller (Fam. Lauraceae) and evaluated for its potential as an alternative to maize starch as a pharmaceutical excipient. Its physicochemical and thermal properties were evaluated and compared with those of maize starch. Granules prepared with avocado and maize starch pastes as binder were evaluated for their flow, friability and compaction characteristics. The average yield of starch extracted from the fresh kernels of P. americana was 20.5 ± 0.55% w/w. The scanning electron micrograph (SEM) showed that avocado starch has two characteristic granule shapes; triangular and circular both having an approximate equal distribution. The triangular shaped granules are larger (28 to 32 µm) than the circular (6 to 9 µm). The foaming capacity of avocado starch was 19.05 ± 0.6%, its swelling, moisture uptake and paste clarity were generally lower than that of the maize starch. Avocado starch gel exhibited an extent of syneresis after freeze–thaw that increased cumulatively with increase in number of freeze–thaw cycles. The glass transition (T_g) and gelatinisation temperatures for avocado starch were higher than that of maize starch. The melting temperatures (T_m), ash value, as well as the various densities of avocado starch showed similarities with those of maize starch. The granules prepared with avocado starch pastes as binder showed superior compactibility and mechanical strength to those of maize starch but with similar flow characteristics. Avocado starch generally showed distinct physicochemical and binder properties with some similarities to the standard maize starch.     

Antifungal activity of chitosan and its application to control post‐harvest quality and fungal rotting of Tankan citrus fruit (Citrus tankan Hayata)

In this study, the antifungal activity of chitosan A (MW = 92.1 kDa) and B (MW = 357.3 kDa), with 94.2% N‐deacetylation were examined at various concentrations against fungi including Penicillium digitatum, Penicillium italicum, Botrydiplodia lecanidion and Botrytis cinerea. The effectiveness of these chitosans to control the post‐harvest quality of Tankan fruit, a popular sub‐tropical citrus fruit, was investigated. It was found that chitosan, depending on type and concentration, caused 25.0–90.5% growth inhibition on test organisms after 5 days of cultivation at 24 °C. Chitosan treatment significantly reduced (P < 0.05) the percentage decay of Tankan fruit during storage at 24 °C. After 42 days of storage at 13 °C, chitosan‐coated Tankan fruits were firmer, exhibited less decay and weight loss, and showed higher titratable acidity, ascorbic acid, and total soluble solids than the control fruit. Weight loss of Tankan fruits decreased as the concentration of chitosan was increased. On the other hand, chitosan A, regardless of concentration tested, was found to be more effective in retaining the firmness, titratable acidity and water content, total solid content and ascorbic acid content of Tankan fruits than chitosan B. Copyright © 2006 Society of Chemical Industry     

Effect of high oxygen modified atmosphere on post‐harvest physiology and sensorial qualities of mushroom

The changes in physiology and sensorial qualities of mushroom stored at 2 °C for 12 days under high oxygen (100% O₂, 80% O₂) atmosphere and air had been investigated. Respiration rate was suppressed in mushroom in 80% O₂ and 100% O₂. No significant differences were found between 80% O₂ and 100% O₂. Weight loss was not more than 1.5% in all treatments. Weight loss and firmness of mushroom held in high oxygen were significantly (P < 0.05) higher than in air. Total soluble solid (TSS) was only slightly affected by high oxygen treatment. High oxygen, especially 100% O₂ treatment was effective at reducing browning degree and electrolyte leakage of mushroom. The surface colour of mushroom changed slightly before tenth day under high oxygen treatment. From day 2 the L‐value of mushroom flesh was significantly (P < 0.05) lower under air atmosphere compared with high oxygen treated mushroom. High oxygen, especially 100% O₂ was effective at inhibiting discoloration. The PPO activity of mushroom was significantly (P < 0.05) higher in 100% O₂ compared with air treatment. The POD activity was highest in high oxygen at eighth day, then reduced. High oxygen, especially 100% O₂ was effective at maintaining the quality of mushroom.     

Effect of γ‐irradiation on post‐harvest ripening of plantain fruit (Musa paradisiaca) cultivars

Three plantain cultivars, Agbagba, Obino L'ewai and Cardaba, harvested at two stages of maturity, were irradiated at 0.1–1.0 kGy prior to storage under tropical ambient conditions. Post‐irradiation storage behaviour showed that plantain fruits at full three‐quarter grade were more responsive to irradiation treatment than at full grade maturity, while Cardaba, a type of cooking banana, showed the least response. Irrespective of varietal differences, irradiation to 0.5 kGy or higher caused severe tissue damage, softening and skin discolouration; however, γ‐irradiation at optimum dose range of 0.15–0.30 kGy effectively delayed ripening for 10–12 days in Agbagba and Obino L'ewai, respectively, without affecting respiratory pattern or fruit quality. © 1999 Society of Chemical Industry     

Control of post‐harvest brown rot on nectarine by Epicoccum nigrum and physico‐chemical treatments

Post-harvest physico-chemical treatments—water at 40 °C or 60 °C (HW), and sodium bicarbonate at 1 or 2.5% (SBC) at 20, 40 and 60 °C—were tested on peaches and nectarines in order to control brown rot caused by Monilinia spp. and to select the best physico-chemical treatment to be used in combination with pre-harvest applications of the biological control agent Epicoccum nigrum (ATCC number 96794). Experiments were carried out in France, Italy and Spain in order to test different experimental conditions. Monilinia rot was reduced in peach and nectarine treated with HW (40 °C for 2 min) in all three countries, the percentage of rot reduction was similar for France, Italy and Spain (over 40%). A synergistic effect between HW at 40 °C during 150 s or at 60 °C during 20 s and SBC was observed in all three countries. After preliminary experiments post-harvest treatment of HW (60 °C) + SBC (1%) during 20 s was selected to combine it with field treatments. Pre-harvest treatments with fungicide or E. nigrum did not reduce brown rot in any country. However, pre-harvest treatments with E. nigrum, chemical fungicide, and their integration followed by post-harvest physico-chemical treatment significantly reduced Monilinia rot compared to pre-harvest untreated fruits followed by post-harvest physico-chemical treatment in Italy (over 70%). Post-harvest treatments with E. nigrum were also tested in Italy on natural and artificial infections in nectarine over 3 years. E. nigrum, as fresh or formulated cells, at a concentration of 10⁸ conidia mL⁻¹ were effective, significantly reducing the incidence of brown rot compared to control, both under artificial and natural infection, from 43 to 100%. Copyright © 2007 Society of Chemical Industry     

Reduction or delay of post‐harvest physiological deterioration in cassava roots with higher carotenoid content

Post‐harvest physiological deterioration (PPD) is one of the most important constraints in cassava production and commercialization. It has been hypothesized that the antioxidant properties of carotenoids in yellow cassava roots may help reduce or delay PPD. The industrial sector prefers cassava with a high dry matter content. The latter has also been reported to have a positive correlation with PPD. The objective of this study was to determine the correlation between both the dry matter and total carotenoid contents and PPD in the roots of 101 cassava clones. PPD was positively but weakly associated with dry matter content (R² = 0.100, P < 0.01), and inversely associated with the total carotenoid content in roots (R² = 0.515, P < 0.01). In addition, total carotenoid content and color intensity were strongly and positively associated (R² = 0.769, P < 0.01), suggesting that the roots of cassava clones with a relatively high total carotenoid content can be selected through a simple visual inspection of the color intensity in the parenchyma. Copyright © 2005 Society of Chemical Industry     

Characterisation of zein–oleic acid films and applications in fruit coating

Pure zein films are known to be very hydrophobic, but are inappropriate for edible coating applications because of their brittle nature. In an attempt to improve the flexibility of these coatings, the influence of low concentrations of oleic acid (OA) as a plasticiser on mechanical, topographical and wetting properties of zein thin films was evaluated. Films were first obtained by casting from aqueous ethanol solutions with 4.0% in mass of zein and additions of 0%; 0.25%; 0.50%; and 1.0% (w/w) of OA. The results indicate an improvement in mechanical properties with increasing plasticiser leading to a reduction in the elastic modulus. An increase in the elongation at break has been observed, but with minor influence on tensile strength. All plasticised zein films have similar initial contact angle (approximately 69°) with a time‐dependent receding drop behaviour. An increase in plasticiser concentration increases film’s affinity towards water. As measured by atomic force microscopy, a consistent linear relation (R² = 0.991) was estimated between film composition and surface adhesion and consequently on the hydrophilicity. Surface topography also varied with plasticiser addition, becoming smoother as the OA concentration increases. When tested as an edible coating on pears (Pyrus communis L.), a formulation with 0.25% wt of plasticiser achieved the best results in preserving the pear mass as measured during the evaluated storage time (12 days) at room temperature. A 0.5% concentration of plasticiser had no influence and higher amounts resulted in a reduction in fruit protection.     

Recent advances in extending the shelf life of fresh Agaricus mushrooms: a review

Postharvest browning of Agaricus mushrooms is a severe problem that reduces the shelf life of harvested mushrooms because of their continued respiration and biochemical activity. There are no simple answers and no single treatment is known to limit overall quality deterioration. However, there are several strategies that are being implemented in order to reduce the rate of respiration for mushrooms. Packaging technology is the common denominator that allows us to implement these strategies and thus is key to quality preservation. In this review, first, the major factors involved in postharvest quality deterioration are discussed and then technological advances/methods used to counteract these hurdles are presented. Copyright © 2010 Society of Chemical Industry     

Influence of nutrient solutions in an open‐field soilless system on the quality characteristics and shelf life of fresh‐cut red and green lettuces (Lactuca sativa L.) in different seasons

BACKGROUND: Little information is available about the impact of nutrient solution ion concentration on quality characteristics and shelf life of fresh‐cut lettuce grown in soilless systems in open field. Three lettuce genotypes, lollo rosso and red oak leaf as red‐leafed genotypes and butterhead as green‐leafed genotype, were studied. The influence of three nutrient solutions with low, medium and high ion concentrations, which varied in the macroanion (NO$_{3}^{-}$ ) and macrocations (K⁺, Ca²⁺ and NH$_{4}^{+}$ ), were compared in summer and winter. RESULTS: The nutrient solutions evaluated in this study for the production of lettuce in a soilless system did not strongly influence the quality characteristics of the raw material. When the ion concentration of the nutrient solution was increased, fresh weight decreased, although it depended on the genotype and season. Maturity index and dry matter content varied with the season but independently of the nutrient solution. In summer, maturity index was higher and dry matter lower than in winter. Initial texture and visual quality were not influenced by the nutrient solution. Medium ion concentration provided the highest content of vitamin C and phenolic compounds. Our observations pointed out that the genotype had a strong influence on the shelf life of the fresh‐cut product with minor differences among nutrient solutions. In general, red‐leafed lettuces showed the highest antioxidant content, helping the maintenance of sensory characteristics throughout storage. CONCLUSION: The combination of optimal nutrient solution ion concentration and suitable cultivar is considered essential to ensure lettuce post‐cutting life. Copyright © 2012 Society of Chemical Industry