In this issue (for selection click on the bullets) Development of tempeh-based snack foods Modified-atmosphere packaging for leafy Asian vegetables Asian vegetables to benefit from joint Research The Australian specialty mushroom industry Evaluation and commercialisation of wasabi production Indian condiments & pickles Update on RIRDC Asian Foods Program Chinese water chestnuts Workshop on bamboo for shoot and timber Production and marketing of Japanese ginger in Tasmania

DEVELOPMENT OF TEMPEH-BASED SNACK FOOD

Seng Kwee

Tempeh is a popular Indonesian fermented food containing cooked soybeans bound together by a dense white mycelium of Rhizopus oligosporus mould into a compact 2 cm thick white cake. It is also popular in other Asian countries, with growing interest internationally, including some European countries, Canada and USA.

Fresh soy tempeh contains an average of 17.5% protein, which compares very favourably with chicken (20.5%), beef (18.4%), hamburger (15.2%), eggs (12.5%) and milk (3.2%). Tempeh is the world's richest known vegetarian source of vitamin B12, one of the ingredients most lacking in vegetarian diets. It is highly digestible because the fermentation process during the manufacture of tempeh partially digests the soy proteins and oils, thus making them more easily absorbed by the body. The fermentation process also increases its palatability and nutritive properties. The mould penetrates the soybean cells, softening the soybeans by mechanically pushing the cells apart. This effect greatly reduces the cooking time, making tempeh a handy, quick-cooking food. It contains 780 kilojoules per 100 grams, is very low in saturated fats and contains no cholesterol. Tempeh contains strong antioxidants which are resistant to the development of rancidity. So tempeh may have potential to prevent or reduce the development of rancidity in a mixture with fatty products such as seafoods or fatty meats. Tempeh-based products have strong appeal on health and nutrition grounds to most consumer groups, and should be useful and attractive to vegetarians.

Tempeh can be sliced in thin (0.5 cm) rectangular shapes and fried till golden brown with a crispy surface. It has a meat-like texture with a pleasant sweet fresh aroma. It can be served as main course meals in place of meat, chicken and fish or as snack foods. Only a few minutes of cooking time is required to prepare tempeh dishes.

There is a limited range of refrigerated or frozen tempeh products available in selected stores in Australia. However the volume of consumption so far is only small. This can be attributed to lack of knowledge of tempeh and its usage among Australians from non-Asian backgrounds. Fresh tempeh needs refrigerated storage and has a limited shelf-life (1 to 2 weeks, under refrigeration in an opened pack). Local tempeh manufacturers produce a small range of refrigerated tempeh products which require minimal cooking prior to consumption, but no shelf-stable tempeh-based snack food products.

This project was undertaken to develop tempeh snack foods which are ready to eat, can be developed to be shelf-stable and to have good keeping quality. Sensory evaluation and market research were included to adjust the product attributes to suit target consumers.

Two shelf stable product types were developed, tempeh bars and tempeh crackers. Focus group and sensory studies were carried out with Australian and Asian consumers during the developmental stages. Both of the consumer groups found that the optimised products were acceptable and found no significant difference (p<0.05) in the overall acceptability of the products. Their microbiological qualities were acceptable. Their potential shelf lives in room temperature for 6 months appeared good.

It is envisaged that the introduction of tempeh into the snack foods market will popularise tempeh to domestic consumers from both Asian and non-Asian cultural backgrounds. The net results of these developments will be an increase in demand for tempeh, which will lead to the industry adopting larger scale production methods to gain economy of scale and enhanced future export potential.

We are particularly keen to hear from commercial companies that are interested in progressing the development of tempeh snack foods.

Dr. Seng Kwee Queensland Horticulture Institute QDPI 19 Hercules Street Hamilton QLD 4007 Phone: (07) 3406 8555 Fax: (07) 3406 8663

MODIFIED-ATMOSPHERE PACKAGING FOR LEAFY ASIAN VEGETABLES

Tim O’Hare, Lung Wong and Amikha Prasad

Many leafy Asian vegetables respond well to atmosphere modification. Reducing the oxygen level and/or increasing the carbon dioxide levels within packaging can significantly increase the shelf-life of these vegetables. The current research is part of a Queensland Horticulture Institute project funded by RIRDC and Mary Valley Plantation.

Shelf-life extension is nowhere as important as with tender ‘juvenile’ vegetables, which are unhardened and therefore susceptible to all forms of stress. Young vegetables have gained increased popularity in the Asian vegetable industry, not only because they are attractive to consumers, but because the growing cycle is considerably shorter than for mature plants.

A value-adding means of supplying vegetables to consumers is known as ‘fresh-processing’. In the vegetable industry, this can involve anything from shredding to peeling to dicing. With Asian leafy vegetables however, it commonly involves the relatively simple procedure of cutting leaves from the stem. Salads and stir-frys can be premixed by packaging several of these vegetables together. This can provide a consumer with a product that involves little if any preparation. Cutting, however, does reduce the shelf-life of leafy vegetables.

Fortunately, the problems with shelf-life can be reduced with modified atmosphere packaging (MAP). As vegetables are a living product, an appropriate atmosphere can be generated by placing the vegetables in a semi-permeable plastic package. As the vegetable breathes it uses up oxygen and generates carbon dioxide. A steady-state atmosphere will be reached when the rate of vegetable respiration matches the permeability characteristics of the plastic used. The plastic to be used is dependent on a number of factors, and has to be tailored for your vegetables.

The first thing needed to be known is: What is the optimum atmosphere for the vegetables? Optimum atmospheres can vary somewhat between vegetables, but with the vegetables we have studied, the optimum fell within 0.5-2% oxygen and 2-5% carbon dioxide.

The second thing needed to be known is: What is the respiration rate of the vegetables when placed under this atmosphere? You need to know this for your packaging design. The respiration of a number of different leaves held at 10°C is shown in Table 1. From this, it can be seen that the respiration rate does not vary widely between the varieties listed. Respiration is affected by a number of factors, but perhaps one of the most important is temperature. The integrity of the cold-chain is very important, as high (non-refrigerated) temperatures will cause a depletion of oxygen and a surplus of carbon dioxide, both of which can damage your product.

Table 1: Permeance characteristics of plastic films required to produce an equilibrium atmosphere of 2%O2 / 5%CO2 for a range of fresh-processed leafy Asian vegetables handled at 10°C. Values are shown for retail (180 g) and wholesale-sized packages (510 g).

Vegetable Respi- ration rate [mlO2 per kg/h] Respi- ration rate [mlCO2 per kg/h] Product weight [g] Package surface [m2] Plastic O2 permeance [mlO2 per m2/day] Plastic CO2 permeance [mlCO2 per m2/day] pak choi 23 27 180 0.086 6100 27100 Brassica rapa var. chinensis     510 0.266 5600 24900 tatsoi 18 17 180 0.086 4800 17100 Brassica rapa var. rosularis     510 0.266 4400 15700 mizuna 24 26 180 0.086 6300 26100 Brassica rapa var. nipposinica     510 0.266 5800 24000 mibuna 22 24 180 0.086 5800 24100 Brassica rapa var. nipposinica     510 0.266 5300 22100 Chin. mustard 25 22 180 0.086 6600 22100 Brassica juncea     510 0.266 6100 20300 garland 16 15 180 0.086 4200 15100 Chrysanthemum coronarium     510 0.266 3900 13800 choi sum 17 20 180 0.086 4500 20100 Brassica rapa parachinensis     510 0.266 4100 18400 mixed salad 22 23 180 0.086 5800 23100       510 0.266 5300 22100

The third thing needed to be known is: what is the package size. That is, what is the plastic film area of the package, and what is the likely weight of product. Once you know these factors, it is only a matter of calculating the required permeability (or rather, the permeance) of your plastic packaging to have a modified atmosphere product. Table 1 shows the predicted plastic permeance required for two bag sizes (retail and wholesale) of a number of vegetables commonly included in salad mixes. Note that the plastic required is different for each size, and is dependent on the ratio of leaf weight to package surface area.

The data shown in Table 1 provides a good basis for developing a modified atmosphere package. The plastic permeance figures shown are theoretical and require practical testing prior to commercial development. Stage two of the project will undertake this testing, as well as developing other mechanisms of shelf-life control that be incorporated into commercial products.

Queensland Horticulture Institute, QDPI 19 Hercules Street, Hamilton QLD 4007 Phone: (07) 3406 8555, Fax: (07) 3406 8663 Mr. Lung Wong, Dr. Tim O'Hare and Mr. Amikha Prasad investigating the use of anti-yellowing technology on fresh-processed pak choi

ASIAN VEGETABLES TO BENEFIT FROM JOINT AUSTRALIAN/CHINESE RESEARCH

Tim O’Hare

Research into postharvest handling of pak choi, Chinese cabbage, broccoli and Oriental bunching onions is expected to receive a boost in July 1998 due to the development of a three year Australian/Chinese project jointly funded by ACIAR (Australian Centre for International Agricultural Research) and RIRDC. Institutes taking part in the project include the Queensland Horticulture Institute (QDPI), the Institute for Horticultural Development (Agriculture Victoria), the University of Adelaide (UA), the Beijing Vegetable Research Center and the Hangzhou Institute of Commerce.

The project is aimed at addressing a number of problems pertinent to the Australian and Chinese marketplaces. Project leader, Dr.Tim O'Hare said "The problems tend to vary, but in essence we are all attempting to improve the shelf-life of a number of key vegetables". Problems range from reducing leaf abscission during long-term storage of Chinese cabbage, to extending the shelf-life of minimally-processed pak choi.

Each research institute will be targeting a different facet of the project. While Dr. O'Hare and his colleagues at the QDPI will be investigating factors controlling leaf yellowing of pak choi, Dr. Klieber's group at UA will be studying factors affecting Chinese cabbage storage, as well as jointly tackling the effect of preharvest factors on postharvest storage with Ms. Trish Grant and Mr. Bruce Tomkins of Agriculture Victoria.

The Chinese institutions will be investigating these problems as well as some specific issues such as marketing broccoli under ambient conditions and modified atmosphere storage of Oriental bunching onions. "There is a certain degree of overlap that will provide a healthy opportunity for exchange of ideas", Dr. O'Hare said.

The project is among the first of its kind to develop a national and international network in this area. Although the project was initially proposed as an ACIAR project, the involvement of RIRDC has enabled increased emphasis on Australian issues within the project. "In a time of increasing financial restriction, co-funding of projects appears to be the best way to generate quality research that can be used by industry", Dr. O'Hare said.

Dr. Tim O'Hare Queensland Horticulture Institute QDPI 19 Hercules Street Hamilton QLD 4007 Phone: (07) 3406 8555 Fax: (07) 3406 8663

 

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