Yasmina Sultanbawa

Cryoprotective effects of sugar and polyol blends in ling cod surimi during frozen storage

Cryoprotectant blends were investigated for their potential to stabilize ling cod surimi during frozen storage at −18°C for 4 months. A central composite rotatable design was used to formulate 25 blends containing lactitol, Litesse™, sucrose, and sorbitol, at final total concentrations of 4–12%. Although decreases in % salt extractable proteins (SEP) (79 → 48%), apparent viscosity (3640 → 390 centipoises) and water binding capacity (WBC) (1.33 → 0.94 g/g) were observed, the gel strength, color, pH and myosin-to-actin ratio did not change significantly after frozen storage of surimi containing any of the cryoprotectant blends. In contrast data observed for surimi with no cryoprotectants were significantly different from those with the cryoprotectant blends over the storage period. All blends gave surimi and cooked gels comparable to those obtained with commercial mix (4% sucrose, 4% sorbitol), with the 4% blend containing 1% of each cryoprotectant being the most economical and the lowest in calorie content.

Effect of the combined application of chitosan and carbonate salts on the incidence of anthracnose and on the quality of papaya during storage

Summary The potential of chitosan (1%) alone, or in combination with ammonium carbonate (3%) or sodium bicarbonate (2%), to reduce the incidence of anthracnose (Colletotrichum gloeosporioides) on papaya (Carica papaya L.) and maintain quality was investigated during storage at 13.5°C and 95% RH for 14 d, and for 2 d under simulated market conditions (25°C, 75% RH). Chitosan alone or in combination with sodium bicarbonate or ammonium carbonate significantly (P < 0.005) reduced the severity of anthracnose in both inoculated and naturally-infected fruit. The effect of chitosan with ammonium carbonate on the incidence and severity of anthracnose was greater than chitosan alone, or chitosan with sodium bicarbonate. Chitosan with ammonium carbonate significantly (P < 0.005) reduced the incidence of anthracnose in, and the recovery of C. gloeosporioides from naturally-infected fruit compared to control fruit. Eating quality was not affected by these post-harvest dip treatments. Chitosan with ammonium carbonate retained high fruit quality, significantly (P < 0.005) retarded colour development of skin and flesh, increased fruit firmness and reduced weight loss. Internal carbon dioxide concentrations increased in chitosan-coated fruit to reach 7% in chitosan and ammonium carbonate-treated fruit. Thus, chitosan combined with ammonium carbonate represents a commercially acceptable, economically viable and effective alternative for post-harvest control of anthracnose during storage of papaya.

Mode of action of chitosan coating on anthracnose disease control in papaya

The effect of a chitosan coating on antifungal activity and rate of respiration, chitinase and β, 1-3 glucanase activities with reference to papaya variety ‘Rathna’ was investigated. One percent chitosan, extracted from locally available prawn waste, was selected as the effective concentration to inhibit spore germination via a series of experiments on potato dextrose agar. Rate of respiration and the concentration of CO2 in the internal cavity of chitosan-treated and untreated papaya were tested via gas chromatography. Chitinase and β,1-3 glucanase activities were tested in peel samples using gel diffusion and spectrophotometric assays, respectively. Complete inhibition of spore germination was observed in-vitro at treatments of 1% chitosan and above. This concentration significantly (P < 0.05) reduced both disease incidence and severity on inoculated fresh papaya. Significant (P < 0.05) decrease was observed in rate of respiration while internal CO2 concentration of the fruit increased (P < 0.05) with the chitosan treatment. Chitinase and β,1-3 glucanase activities of papaya variety Rathna subjected to chitosan treatment were much higher than in the untreated control. Chitosan shows antifungal activity to the anthracnose disease causing fungus and stimulates the defense response on the papaya peel by increasing the chitinase and β,1-3 glucanase activities. The antifungal activity of chitosan could be attributed to the induction of elicitation activity due to these defense enzymes. It also forms a semi-permeable coating around the fruit and extends storage life of papaya by reducing the rate of respiration and delaying ripening.

Effect of Packaging Materials and Storage on Major Volatile Compounds in Three Australian Native Herbs

Lemon myrtle, anise myrtle, and Tasmanian pepper leaf are commercial Australian native herbs with a high volatile or essential oil content. Packaging of the herbs in high- or low-density polyethylene (HDPE and LDPE) has proven to be ineffective in preventing a significant loss of volatile components on storage. This study investigates and compares the effectiveness of alternate high-barrier property packaging materials, namely, polyvinylidene chloride coated polyethylene terephthalate/casted polypropylene (PVDC coated PET/CPP) and polyethylene terephthalate/polyethylene terephthalate/aluminum foil/linear low-density polyethylene (PET/PET/Foil/LLDPE), in prevention of volatile compound loss from the three native herbs stored at ambient temperature for 6 months. Concentrations of major volatiles were monitored using gas chromatography-mass spectrometry (GC-MS) techniques. After 6 months of storage, the greatest loss of volatiles from lemon myrtle was observed in traditional LDPE packaging (87% loss) followed by storage in PVDC coated PET/CPP (58% loss) and PET/PET/Foil/LLDPE (loss of 23%). The volatile loss from anise myrtle and Tasmanian pepper leaf stored in PVDC coated PET/CPP and PET/PET/Foil/LLDPE packaging was <30%. This study clearly indicates the importance of selecting the correct packaging material to retain the quality of herbs with high volatile content.

Organic acids in Kakadu plum (Terminalia ferdinandiana): the good (ellagic), the bad (oxalic) and the uncertain (ascorbic)

The phenolic ellagic acid (EA) is receiving increasing attention for its nutritional and pharmacological potential as an antioxidant and antimicrobial agent. The Australian native Kakadu plum (Terminalia ferdinandiana) fruit is an abundant source of this phytochemical. The fruit also contains large amounts of vitamin C (mainly as ascorbic acid, AA) and possibly the undesirable oxalic acid (OA). Regular consumption of high oxalate foods poses a variety of health risks in humans including interference with calcium absorption and kidney stone formation. Oxalate is also the end-product of AA metabolism so that consumption of fruit with heightened AA content has the potential to elevate urinary oxalate levels. The aims of this study were to investigate the distribution of EA and the presence of other bioactives in other Kakadu plum tissues. Chemical analysis of Kakadu plum fruit and leaves for EA (free and total), OA (water-soluble and total), calcium (Ca) and AA indicated that EA and AA concentrations were high in the fruit while the leaves had significantly higher EA levels but little or no detectable AA. OA content in fruit and leaves was substantial with the fruit being placed in the high-Oxalate category. These findings suggest that there is potential to elevate oxalate levels in the urine of susceptible people and intake of fruit-derived products should be closely monitored. By measuring tissues collected from specific trees, high EA-producing or low OA-containing individuals were identified.

Betalain rich functional extract with reduced salts and nitrate content from red beetroot (Beta vulgaris L.) using membrane separation technology

An initial laboratory-scale evaluation of separation characteristics of membranes with nominal molecular weight cut-offs (NMWCO) ranging from 30kD down to 0.5kD indicated effective separation of betalains in the 0.5kD region. Subsequent pilot-level trials using 1kD, loose reverse osmosis (LRO) and reverse osmosis (RO) spiral-wound membranes showed LRO membrane to be very efficient with up to 96% salt and 47% other dissolved solids removed while retaining majority of the pigment (∼98%) in the betalain rich extract (BRE). The total betalain content in the BRE increased up to 46%, the highest recovery reported so far at pilot scale level. Interestingly, more than 95% of the nitrates were removed from the BRE after the three diafiltrations. These studies indicate that membrane technology is the most efficient technique to produce BRE with highly reduced amounts of salts and nitrate content.

Fish Silage as Replacement of Fishmeal in Red Tilapia Feeds

We estimated the effect on growth and nutrient efficiency of replacing fishmeal with silage incorporated with rice bran in diets for fingerling red tilapia (Oreochromis mossambicus × Oreochromis niloticus × Oreochromis aureus) over 12 weeks. Isonitrogenous (300 g kg−1 protein dry matter basis) and isoenergetic (4450 Kcal gross energy kg−1) feed formulations with increasing levels of tilapia silage as a replacement for fishmeal were prepared: Diet 1 with no silage (0 g Kg−1), Diet 2 (250 g Kg−1), Diet 3 (500 g Kg−1), and Diet 4 (750 g Kg−1). Feed intake was similar among Diets 1, 2, and 3, while Diet 4 had a significantly lower intake. There was no significant difference (P > 0.05) in weight gain or specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER), among fish fed Diets 1, 2, and 3. Fish fed with Diet 4 had significantly lower weight gain; SGR and PER and significantly higher FCR. Organoleptic properties of the fish were not affected by the diets. The results of this study indicate that less expensive dried fish silage with rice bran is an alternative protein source for tilapia feed up to 50% of fishmeal replacement.

A novel photosensitization treatment for the inactivation of fungal spores and cells mediated by curcumin

The global concerns regarding the emergence of fungicide-resistant strains and the impact of the excessive use of fungicidal practises on our health, food, and environment have increased, leading to a demand for alternative clean green technologies as treatments. Photosensitization is a treatment that utilises a photosensitiser, light and oxygen to cause cell damage to microorganisms. The effect of photosensitization mediated by curcumin on Aspergillus niger, Aspergillus flavus, Penicillium griseofulvum, Penicillium chrysogenum, Fusarium oxysporum, Candida albicans and Zygosaccharomyces bailii was investigated using three methods. The viability of spores/cells suspended in aqueous buffer using different concentrations of curcumin solution (100-1000μM) and light dose (0, 24, 48, 72 and 96J/cm2) were determined. Spraying curcumin solution on inoculated surfaces of agar plates followed by irradiation and soaking spores/cells in curcumin solution prior to irradiation was also investigated. In aqueous mixtures, photosensitised spores/cells of F. oxysporum and C. albicans were inhibited at all light doses and curcumin concentrations, while inactivation of A. niger, A. flavus P. griseofulvum, P. chrysogenum and Z. bailii were highly significant (P<0.001) reduced by 99%, 88.9%, 78%, 99.7% and 99.2% respectively. On the surface of agar plates, spores/cells exposed to a light dose of 360J/cm2 sprayed with curcumin at 800μM showed complete inhibition for A. niger, F. oxysporum, C. albicans and Z. bailii, while A. flavus P. griseofulvum, and P. chrysogenum reduced by 75%, 80.4% and 88.5% respectively. Soaking spores/cells with curcumin solution prior to irradiation did not have a significant effect on the percentage reduction. These observations suggest that a novel photosensitization mediated curcumin treatment is effective against fungal spores/cells and the variation of percentage reduction was dependent on curcumin concentration, light dosage and fungal species.

Phytochemicals and nutritional composition in accessions of Kei-apple (Dovyalis caffra): Southern African indigenous fruit

Current study was initiated to identify the phytochemicals and the nutritional profile of eleven Kei-apple fruit accessions. Accession FH29 showed the highest level (492.45 mg 100 g-1 fresh weight) of total phenolic content, higher than the referral fruit, blueberry. Pyrogallol was identified as the predominant phenolic compound in all accessions. Accession FH 29 showed the highest (49.75 µmol TEAC g-1 fresh weight) antioxidant capacity. Catechin content was higher in accessions; FH151, FH15, FH14, FH29, FH243, FH 239 and FH 231. Accessions, FH14 and FH232 exhibited higher levels of β-carotene than the referral fruit apples (cv. Top red) and peaches (cv. Excellence). The total sugar (glucose and fructose) was highest (50 mg g-1 fresh weight) in accession FH240. Asparagine (3122.18 mg L-1) and gamma-aminobutyric (1688.87 mg L-1) were higher in accessions FH239 and FH243 respectively. Overall, the accession Kei-apple FH236 can be regarded as a good source of essential amino acids.

Bioactive rich extracts from Terminalia ferdinandiana by enzyme-assisted extraction: a simple food safe extraction method

A food grade compatible enzyme assisted extraction (EAE) technique for extracting bioactive compounds from freeze-dried Kakadu plum puree was evaluated. To optimise the extraction, a central composite rotatable design (CCRD) was conducted and effects of solvent concentration, enzyme concentration and time of reaction on extracted levels of free ellagic acid (fEA), ascorbic acid (AA) and total phenolic content (TPC) were determined. In the extracts, concentration of fEA ranged from 53.6 to 266.6 mg/100 g dry weight (DW) of Kakadu plum puree; AA 63.7 to 112.1 mg/100 g DW and TPC levels of 73.23 to 104.74 mg of gallic acid equivalent (GAE)/g. Extraction yield of fEA ranged from 10.3 to 51.3%. The model was found to be suitable for extraction of fEA - an important bioactive compound with documented antimicrobial properties from Kakadu plum fruit. A solvent (propylene glycol) concentration of 1.5% (w/w), enzyme (pectolytic enzymes) concentration of 300 mg/L and extraction time of 15 h was ascertained as optimum for the fEA extraction delivering a yield of 51.3%. The extraction method described here facilitates the provision of a simple, cost effective food-grade compatible extract that by-passes the need for organic solvents thereby obtaining an EA-rich aqueous extract with enhanced biological activities. This simple extraction method can also be applied to other EA rich plant material like pomegranate and peel of many common fruits which are generated as food processing by-products and can be easily adopted by numerous industries.