Bioconversion of Organic Residues for Rural Communities (UNU, 1979, 178 p.): Nutritional evaluation in humans: The evaluation of various food products

Bioconversion of Organic Residues for Rural Communities (UNU, 1979, 178 p.)

From the charter of the United Nations University

Foreword

Perspectives on bioconversion of organic residues for rural communities

(introduction...)

Introduction

Sources of available nutrients

The most suitable materials for bioconversion

Characteristics of residues

Bioconversion systems

Physical and chemical treatments

Microbial conversion

The animal conversion phase

Summary

References

Availability of organic residues as a rural resource

(introduction...)

Discussion summary: Papers by van der Wal and Barreveld

Micro-organisms as tools for rural processing of organic residues

(introduction...)

Introduction

Microbial utilization of mono- and di-saccharide residues

Microbial conversion of starchy residues

Microbial conversion of complex mixtures of compounds (Polysaccharides, Proteins, Lipids, etc.)

Microbial utilization of cellulose and ligno-cellulose residues

Algal culture as a source of biomass

Microbial utilization of silviculture biomass

Micro-organisms and marine and freshwater biomass

International studies on processing organic residues

References

Production of feed as an objective for bioconversion systems

(introduction...)

Introduction

General characteristics

Manure as feed

Sewage-grown micro-algae

Conclusion

References

Environmental goals for microbial bioconversion in rural communities

(introduction...)

Introduction

Health and water economy

Fertilizer and energy economy

Concluding remarks

References

Discussion summary: Papers by Porter, Berk and La Rivi�re

Strategies for developing small-scale fermentation processes in developing countries

(introduction...)

References

Discussion summary

Production of microbial protein foods on edible substrates, food by-products, and ligno-cellulosic wastes

(introduction...)

Preface

Introduction

Contributions to the solution of nutritional problems

Development of protein-rich vegetarian meat substitutes in the western world

References

Discussion summary

The role of ruminants in the bioconversion of tropical byproducts and wastes into food and fuel

(introduction...)

Introduction

Nutritional limitations in the use of tropical by-products and waste

Practical experience with tropical by-products and wastes as feed for ruminants

An integrated system for converting tropical feeds and byproducts into milk, beef, and fuel

References

Discussion summary

Possible applications of enzyme technology in rural areas

(introduction...)

Introduction

Biocatalytic processes

Enzyme hydrolysis of manioc

Whole cell systems

Cellulose degradation and utilization

Transfer of enzyme technology to rural communities

Conclusions

References

Discussion summary

Indian experience with treated straw as feed

(introduction...)

Introduction

Experience with straw treatment

Field testing and demonstration of straw treatment

General considerations

Summary

Annex 1. The energy efficiency of the two-stage, feed-fuel processing of straw in indian villages

Annex 2. Method of calculating the value presented in table 2 for the efficiency of naoh energy usage

Annex 3. Recommendations to farmers on the treatment of straw

Annex 4. Calculated efficiency of milk production by straw-fed village buffaloes

References

Discussion summary

Indian experience with algal ponds

(introduction...)

Introduction

Cultivation of algae in wastes for feed

Problems of contamination

Cultivation of algae for biofertilizer

References

Acknowledgements

Discussion summary

Organic residues in aquaculture

(introduction...)

Introduction

The range of production in aquaculture

The value of organic wastes

Direct feeding

Concluding remarks

References

Discussion summary

Biogas generation: developments. Problems, and tasks - an overview

(introduction...)

Introduction

What is biogas?

Microbiology of CH4, or bio-methanogenesis

The biogas plant-some technical considerations

Environmental and operational considerations

Developments and processes for rural areas

Cost-benefit analyses

Health hazards

Bottlenecks, considerations, and research and development

References

Discussion summary

Mushroom production technology for rural development

(introduction...)

Materials and methods for growing mushrooms under natural or field conditions

Growing mushrooms under semicontrolled conditions

Results and discussion

References

Discussion summary

The combination of algal and anaerobic waste treatment in a bioregenerative farm system

(introduction...)

Introduction

Algae production on organic wastes

The bioregenerative farm

References

Discussion summary

A continuous composting system for disposal and utilization of animal wastes at the village level

(introduction...)

Status of land utilization and disposal of animal wastes

A continuous composting system for land utilization of animal wastes at the village level

References

Bioconversion of fruit and vegetable wastes

(introduction...)

State of the art of bioconversion

Technical transfer

Integrated research on agricultural waste reclamation

(introduction...)

Introduction

Production of yeast from soybean cooking waste at miso factories

Application of soy waste as koji substrate for rice miso manufacturing (5, 6)

Conclusion

References

Discussion summary

Solid state fermentation of starchy substrates

(introduction...)

Introduction

Materials and methods

Agro-economic perspectives

Summary

References

Discussion summary

Production of single-cell protein from cellulose

(introduction...)

Introduction

Experimental results

Discussion

Summary

References

Acknowledgements

Discussion summary

Analysis of energy cost of integrated systems

(introduction...)

Energy cost and energy requirement

Why energy analysis?

Net energy intensity

What criteria are offered by energy analysis?

Conclusion

References

Analysis of bioconversion systems at the village level

(introduction...)

Introduction

Approach to bioconversion analysis

Some results and costs from integrated systems

Future development possibilities

Conclusions

Summary

References

Nutritional evaluation of bioconversion products for farm animals

(introduction...)

Introduction

Testing procedures for determination of nutritional value

Bioconversion products: toxicology - problems and potential

(introduction...)

Summary

References

Nutritional evaluation in humans

(introduction...)

Introduction

Evaluation of products of bioconversion for human consumption

Procedures for nutritional evaluation in humans

The evaluation of various food products

Concept of productivity

Conclusions

References

Discussion summary: Papers by van Weerden, Shacklady, and Bressani

Biomass from organic residues for animal and human feeding

(introduction...)

References

Discussion summary

Appropriate biotechnology - summary remarks

(introduction...)

References

Other UNU Publications

(introduction...)

Books

The evaluation of various food products

Food Products Derived from Animals

Domestic animals such as ruminants, swine, and poultry will probably be fed more and more products containing materials from bioconversion processes. It is not expected, however, that this practice will change the quality of the protein derived from the animals. Changes in the chemical composition of animal tissues may occur, as well as deposition in the tissues of heavy metals, insecticide and herbicide residues, and other additives. If the levels of these substances become too high, the animals will show a decrease in overall performance, which, in turn, should lead to elimination of the product from the feed. If the animals gain weight and show good feed-conversion efficiency and overall performance, it is a good indicator that food products made from such animals will be of high enough quality to be used for human feeding. This, however, does not imply that quality control evaluation should not be carried out on food products obtained from animals fed bioconversion products or biomass (6).

TABLE 1. Protein Intake for Nitrogen Equilibrium Using the Conventional and Short-Term NBI (g/kg) in Adult Human Subjects

Protein source	Conventional	Short-term
Soy isolate	0.67	0.54
Milk	0.63	0.62
50/50 beef/soy	0.59	0 57
Beef	0.64	0.53

Source: Bressani et al. (8).

Conventional Fermented Foods

Fermented foods have been consumed for a long time by populations living in various parts of the world. Although there are several kinds, only three will be discussed in terms of protein quality. These are: (a) foods such as tempeh, a fermented food based on soybeans, a high-oil, high-protein seed; (b) fermented foods based on cereal grains, mainly rice, and (c) fermented foods based on starchy foods such as cassava.

The impact of the fermentation process on the protein quality of the end-product will be considered first. To predict its protein quality, it is essential to know the value of the starting material and the value of the biomass itself. In the case of tempeh, soybean protein is deficient in sulphur amino acids and rich in lysine. The biomass produced on it also contains protein deficient in sulphur amino acids and rich in lysine. Therefore, the protein quality of tempeh will be equivalent to the average of the protein content in the soybean and in the fermented biomass, depending on the amount of protein supplied by each source.

There are no data available on the protein quality of biomass produced on cereal grains. Cereal-grain protein, however, is deficient in lysine, while microbial protein is a rich source of this amino acid. Table 2 shows the nutritional impact of small amounts of yeast added to maize, wheat, and rice. In each case, there is a significant increase in protein quality, suggesting that production of biomass on cereal grains for human feeding would be beneficial to the consumer, assuming that the product would be acceptable organoleptically (9 - 11).

TABLE 2. Supplementary Effect of Small Amounts of Torula Yeast Added to Various Cereal Grains

Cereal grain	Amount of torula added (%)	Protein quality PER
Maize	0	1.23
	3	2.06
Whole wheat	0	1.81
	4	2.17
Wheat flour	0	0.82
	8	2.18
Rice	0	1.87
	6	3.13

Sources. Bressani and Marenco (9); Jarquin et al (10); Elias et al. (11).

There have been few nutritional studies on the protein value of biomass grown on starchy foods. Therefore, to predict its possible use, the analogy of supplementing cassava with beans will be used. SCP and legume foods are also deficient in sulphur amino acids and rich in lysine. The results in Figure 4 show that body weight in rats is maintained when cassava is supplemented with 30 per cent of beans, providing 7.5 9 of protein. However, when bean protein is supplemented with methionine, the body-weight gain of rats fed the bean-cassava diet is maintained with only 15 per cent of beans, providing about 4.5 9 of protein. These results imply that, in order to increase protein content in starchy foods by biomass production, the protein content should be higher than 8 per cent to maintain body weight in experimental animals.

Algae

Algae have been used as food for centuries. They form a part of the diet of the people living around Lake Chad in Africa, and were eaten by the Aztecs in Mexico. Among the several thousands of green and blue algae known, the following have been found adequate for large- or small-scale cultivation: the green algae, Chlorella vulgaris, Scenedesanus acutus, Coelastrum proboscideum, and the blue-green algae, Spirulina maxima. The following discussion of algae is based on information from other laboratories, as we have not gone beyond chemical and animal studies with Microcystis sp. (12).

Figure. 4. Nutritional Significance of Bean Protein Quantity and Quality to Cassava-Based Diets

TABLE 3. Some Observations Made on Human Subjects Fed Algae Protein (10 to 500 g/day)

Unacceptable smell
Disagreeable flavour
Poor appearance of food
Gastro-intestinal discomfort
Poor digestibility of nutrients
Nausea at high levels of intake
Urine and blood analyses normal
After additional processing:
More acceptable organoleptically
Gastro-intestinal problems persisted

Not many results have been reported recently on nutritional evaluation trials using algae grown on different types of biomass for human subjects. This is probably not due to a lack of interest in manufacturing such products, but rather to the initial results obtained in 1963 - 68 that showed a variety of adverse effects in subjects fed algae or other SCPs. As shown in Table 3, clinical trials with algae were particularly discouraging (13 - 17). Most materials containing algal protein showed low digestibility for most nutrients, and caused gastrointestinal discomfort. Unacceptable smell, taste, and disagreeable flavour produced nausea. However, it became evident that further processing by alcohol extraction improved the product significantly.

In more recent reports, materials produced and processed by improved technologies have yielded products that offer more promise. Some of these results are shown in Tables 4 and 5, indicating better protein digestibility and biological value, while urine and blood analyses are no different from those observed after feeding casein, a universally acceptable protein. However, it is costly to create acceptable foods from algae. These results suggest that the production of such materials for rural communities would be better directed towards animal feed, where they will be more beneficial to man in the long run.