Production and characterisation of ZESPRI gold kiwifruit vinegar : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University

Pages 61, 83-84 missing from original copyGold kiwifruit (Hort 16A) is a relatively new entrant into the international fresh fruit market and is a controlled variety only marketed by Zespri™. Zespri™ gold and the traditional green 'Hayward' kiwifruit are mainly marketed as fresh whole fruit; however there is interest in extending the range of processed products for gold fruit to provide further opportunities to utilize the increasing volumes now becoming available. Vinegar was selected for investigation as it plays an important role in food processing as a condiment, acidulant and preservative, and has also been identified to have various health benefits. The aims of the project were: (1) To evaluate the effect of juice extraction techniques and conditions on juice yield and quality. (2) To evaluate the effects of pre-fermentation treatment and fermentation conditions on the fermentation behaviour and quality of Zespri gold kiwifruit mashes. (3) To identify suitable conditions for acetifcation of Zespri™ gold kiwifruit wines and investigate the effect of the vinegar elaboration technique on the quality of the resultant kiwifruit vinegars. Ripe peeled or unpeeled gold kiwifruit was processed in a hammer mill and the juice was extracted using a laboratory scale hydraulic press. Yield was measured for four pressurization cycles, to a maximum pressure of 250MPa. Press aid, and pre-(cellulase) and post-pressing (pectinase) enzymes were used to improve juice yield and quality. Juice yield increased through the first three pressing cycles, but there was little gain in the fourth cycle. A juice of suitable clarity and consistency, and yield of 3.8 L.(5 kg pulp)-1 was obtained with the recommended process conditions of: 2 or 3%(w/w) press aid, 0.15mL.kg-1 pre-press enzyme held at 50°C for 2h, 0.035mL.kg-1 post-press enzyme. Repeated pressing was found to increase total phenolics but reduced colour intensity in juice. The free-run juice was superior in colour and TP; other physico-chemical parameters were not affected by repeated pressing. Hand peeling and holding pomace at 30-50°C for 2-6h slightly reduced total acidity and significantly (P<0.05) reduced vitamin C. Skin contact and temperature (30-50°C. 2-6h) significantly (P<0.05) increased total phenolics. The character impacting aromatic compounds, ethyl butanoate, hexanal and trans-2-hexanal, were identified in the juice at 10.8, 4.2 and 9.8mg.L-1, respectively. Proteolytic activity attributed to actinidin was about 45% of that observed in 'Hayward' green kiwifruit juice. Alcoholic fermentation behaviour was evaluated at 20, 30 and 37°C for natural juice and juice supplemented with sucrose to 18°Brix using a wine yeast strain of Saccharomyces cerevisiae. Juices obtained from peeled and unpeeled fruit, filtered and unfiltered, were fermented. With sucrose enrichment, wines with 8.1%w/v or 8.0%w/v were obtained at efficiencies of 88% and 87% and productivities of 1.3 and 1.6g.L-1h-1 at 20 and 30°C, respectively. Natural juice at 20°C gave a similar yield but efficiency and productivity varied from 84-96% and 1.1-0.8g.L-1h-1, respectively. Both sucrose enrichment and high fermentation temperature reduced total vitamin C and total acidity in wine. Many esters which impact positively were identified by GC-MS in the gold kiwifruit wines. These included isoamyl acetate, ethyl acetate, ethyl butanoate, 1-hexy hexanoate, ethyl decanoate and ethyl octanoate. Gold kiwifruit wines with up to 7.5%w/v ethanol were subjected to acetic acid fermentation using a commercial cider vinegar as the inoculum. A start up protocol for a simple semi-continuous fermentation system was developed. The best fermentation conditions identified were 29±2°C with flow rate of 0.8L.min-1 of oxygen enriched (40%) air. A yield of up to 5.8% w/v acetic acid was obtained at an efficiency of 85% and productivity of 1.2g.L-1h-1. A sensory panel described the gold kiwifruit vinegar as having stronger wine character than commercial cider vinegar, and equal to cider vinegar in terms of fruity aroma, ethyl acetate aroma and overall impression. The vinegar was found to have a meat tenderizing effect comparable to commercial papain enzyme and left the meat in good eating condition. Gold kiwifruit vinegar could find a niche market as marinating vinegar

Sustainable management of cassava processing waste for promoting rural development

Cassava is the third-most important food source in the tropics after rice and maize. Cassava is the staple food for about half a billion people in the World. It is a tropical crop grown mainly in Africa, Asia, and South America. It can be cultivated on arid and semiarid land where other crops do not thrive. During the processing of cassava into chips, flour or starch, enormous amount of wastes are generated ca. 0.47 tons for each ton of fresh tubers processed. This waste consists of peels, wastewater and pulp that contain between 36 to 45% (w/w) of starch and from 55 to 64% (w/w) of lignocellulosic biomass. An innovative processing system is therefore essential to take into account the transformation of this waste into value added products. This will address both the environmental pollution and inefficient utilization of these resources. The starch and lignocellulosic cassava processing waste can be converted into renewable energy carriers such as biogas through anaerobic digestion (AD), bio-ethanol through fermentation and bio-hydrogen through dark fermentation. In the case of AD, the waste can be used directly as substrate while for fermentation; the waste must be pre-treated to release monomeric sugars, which are substrates for bioethanol and bio-hydrogen production. There is possibility of sequential fermentation for either bio-ethanol or bio-hydrogen and AD for biogas production thereby making use of all the fractions of the cassava waste. Generation of renewable energy from cassava waste could benefit rural populations where access to electricity is very poor. This would also reduce the dependence on firewood and charcoal that are known to provide almost 90 percent of domestic energy requirements. Such a development could help save trees, lower emissions that cause climate change and reduce the fumes from millions of tons of firewood that threaten human health, especially the health of women and children. Although deforestation and land degradation are well-known, the charcoal and firewood consumption that causes them is still on the rise. This chapter, therefore, explores the use of cassava waste for production of fuel energy with a focus for use as domestic cooking fuel. It also proposes an efficient approach to cassava processing to ensure efficient resource utilization in which every part of the tuber is converted to value added products mitigating environmental pollution and improving human health

High temperature simultaneous saccharification and fermentation of starch from inedible wild cassava (Manihot glaziovii) to bioethanol using Caloramator boliviensis.

The thermoanaerobe, Caloramator boliviensis was used to ferment starch hydrolysate from inedible wild cassava to ethanol at 60°C. A raw starch degrading α-amylase was used to hydrolyse the cassava starch. During fermentation, the organism released CO2 and H2 gases, and Gas Endeavour System was successfully used for monitoring and recording formation of these gaseous products. The bioethanol produced in stoichiometric amounts to CO2 was registered online in Gas Endeavour software and correlated strongly (R(2)=0.99) with values measured by HPLC. The organism was sensitive to cyanide that exists in cassava flour. However, after acclimatisation, it was able to grow and ferment cassava starch hydrolysate containing up to 0.2ppm cyanide. The reactor hydrogen partial pressure had influence on the bioethanol production. In fed-batch fermentation by maintaining the hydrogen partial pressure around 590Pa, the organism was able to ferment up to 76g/L glucose and produced 33g/L ethanol

High temperature simultaneous saccharification and fermentation of starch from inedible wild cassava (Manihot glaziovii) to bioethanol using Caloramator boliviensis.

The thermoanaerobe, Caloramator boliviensis was used to ferment starch hydrolysate from inedible wild cassava to ethanol at 60°C. A raw starch degrading α-amylase was used to hydrolyse the cassava starch. During fermentation, the organism released CO2 and H2 gases, and Gas Endeavour System was successfully used for monitoring and recording formation of these gaseous products. The bioethanol produced in stoichiometric amounts to CO2 was registered online in Gas Endeavour software and correlated strongly (R(2)=0.99) with values measured by HPLC. The organism was sensitive to cyanide that exists in cassava flour. However, after acclimatisation, it was able to grow and ferment cassava starch hydrolysate containing up to 0.2ppm cyanide. The reactor hydrogen partial pressure had influence on the bioethanol production. In fed-batch fermentation by maintaining the hydrogen partial pressure around 590Pa, the organism was able to ferment up to 76g/L glucose and produced 33g/L ethanol

High bioethanol titre from Manihot glaziovii through fed-batch simultaneous saccharification and fermentation in Automatic Gas Potential Test System.

A process for the production of high bioethanol titre was established through fed-batch and simultaneous saccharification and fermentation (FB-SSF) of wild, non-edible cassava Manihot glaziovii. FB-SSF allowed fermentation of up to 390g/L of starch-derived glucose achieving high bioethanol concentration of up to 190g/L (24% v/v) with yields of around 94% of the theoretical value. The wild cassava M. glaziovii starch is hydrolysable with a low dosage of amylolytic enzymes (0.1-0.15% v/w, Termamyl® and AMG®). The Automatic Gas Potential Test System (AMPTS) was adapted to yeast ethanol fermentation and demonstrated to be an accurate, reliable and flexible device for studying the kinetics of yeast in SSF and FB-SSF. The bioethanol derived stoichiometrically from the CO2 registered in the AMPTS software correlated positively with samples analysed by HPLC (R(2)=0.99)

Production of raw starch-degrading enzyme by Aspergillus sp. and its use in conversion of inedible wild cassava flour to bioethanol.

The major bottlenecks in achieving competitive bioethanol fuel are the high cost of feedstock, energy and enzymes employed in pretreatment prior to fermentation. Lignocellulosic biomass has been proposed as an alternative feedstock, but because of its complexity, economic viability is yet to be realized. Therefore, research around non-conventional feedstocks and deployment of bioconversion approaches that downsize the cost of energy and enzymes is justified. In this study, a non-conventional feedstock, inedible wild cassava was used for bioethanol production. Bioconversion of raw starch from the wild cassava to bioethanol at low temperature was investigated using both a co-culture of Aspergillus sp. and Saccharomyces cerevisiae, and a monoculture of the later with enzyme preparation from the former. A newly isolated strain of Aspergillus sp. MZA-3 produced raw starch-degrading enzyme which displayed highest activity of 3.3 U/mL towards raw starch from wild cassava at 50°C, pH 5.5. A co-culture of MZA-3 and S. cerevisiae; and a monoculture of S. cerevisiae and MZA-3 enzyme (both supplemented with glucoamylase) resulted into bioethanol yield (percentage of the theoretical yield) of 91 and 95 at efficiency (percentage) of 84 and 96, respectively. Direct bioconversion of raw starch to bioethanol was achieved at 30°C through the co-culture approach. This could be attractive since it may significantly downsize energy expenses

Characterisation and evaluation of a novel feedstock, Manihot glaziovii, Muell. Arg, for production of bioenergy carriers: Bioethanol and biogas.

The objective of this study was to characterise and evaluate a wild inedible cassava species, Manihot glaziovii as feedstock for bioenergy production. Tubers obtained from 3 different areas in Tanzania were characterised and evaluated for bioethanol and biogas production. These bioenergy carriers were produced both separately and sequentially and their energy values evaluated based on these two approaches. Composition analysis demonstrated that M. glaziovii is a suitable feedstock for both bioethanol and biogas production. Starch content ranged from 77% to 81%, structural carbohydrates 3-16%, total crude protein ranged from 2% to 8%. Yeast fermentation achieved ethanol concentration of up to 85g/L at a fermentation efficiency of 89%. The fuel energy of the bioethanol and methane from flour-peels mix ranged from 5 to 13 and 11 to 14MJ/kgVS, respectively. Co-production of bioethanol and biogas in which the peels were added to the fermentation residue prior to anaerobic digestion produced maximum fuel energy yield of (15-23MJ/kgVS)

Combined production of bioethanol and biogas from peels of wild cassava Manihot glaziovii

Cassava peels were pre-treated with alkali, enzyme and in sequential combination of alkali and enzyme, and used for production of bioethanol or biogas, or both (in sequence, bioethanol followed by biogas). The Biogas Endeavour and Automatic Methane Potential Test Systems were used for production of bioethanol and biogas, respectively. The bioethanol yield and volumetric productivity achieved with alkali pre-treatment combined in sequence with enzyme pre-treatment were 1.9 mol/mol and 1.3 g/L/h which was higher than the yield (1.6 mol/mol) and volumetric productivity (0.5 g/L/h) obtained from only enzyme pre-treated peels. Alkali combined in sequence with enzyme was proven to be the best treatment showing a 56% improvement in methane yield compared to the yield from untreated sample. Combined ethanol and methane production resulted in 1.2-1.3-fold fuel energy yield compared to only methane and 3-4-fold compared to only ethanol production. This study therefore provides practical data on the scenario best suited for the harnessing of energy from cassava peels. (C) 2015 Elsevier B.V. All rights reserved