At 4:17 a.m., on a cold and cloudy day in early January, 20,000 bushels of yellow soybeans were loaded into a shipping bin, sampled for purity and weighed at the huge Bunge grain elevators in New Orleans. Under the approving gaze of men in orange coveralls and gray hardhats, the bin then made a 200-yard. conveyor-belt journey to the Mississipi waterfront for loading on the Holland-bound Malmland.

It was the unpretentious beginning of a near epoch in American agriculture: The U.S. government - those men in the coveralls and hardhats - had taken over the inspection and weighing of grain exports to assure foreign buyers of the quantity and quality of their purchases.

Those assurances are designed to bring honesty to a grain export system racked by three years of disclosures of multimillion-dollar cheating schemes by grain workers, former inspectors and corporate officials . The scandals have brought far-reaching change to the grain business, including.

A new government agency, the Federal Grain Inspection Service, to directly weigh and sample 75 per cent of the bilions of dollars of grain exports each year and to supervise state officials weighing and testing the remainder.

A stepped-up national licensing system in which the inspection service will designate inspectors of dosmetic grain under strict new conflict-of-interest regulations and authority to temporarily perform inspections, if necessary, to assure accuracy.

Indictments of 75 individuals, and 14 companies including five major grain firms and 24 empolyees of local or state inspection agencies; there have been 84 convictions so far, the most recent of four companies in New Orleans on Feb.8.

Agreemnets between the government and nine export companies in which stringent new anti-corruption measures are in effect at 35 export elevators; five in those agreements were the fruit of criminal proceedings.

"We are effectively rebuilding integrity in the American grain marketing system," says Donald E. Wilkinson, interim administrator of the Federal Grain Inspection Service. That has become more important now as world food production expands, increasing the supply of grain while demand declines.

"With a smaller market and more competition, price and quality become more of a factor," Ken Murray of the Foreign Agriculture Service said of the grain exporting nations' scramble for sales. U.S. grain exports accounted for more than half $12.5 billion, of the nation's $22 billion export income from farm products in each of the past two years.

"Corruption presents a serious threat to continued demand for American grain exports in overseas markets." Wilkinson told Congress last month. "Although much of the blame dfor the abuses uncovered to date falls on the shoulders of those members of the industry who took unscrupulous advantage of a system that has since been proven to be inherently weak, the system itself was also to blame."

Under that system, the federal government had virtually no responsibility for the accurate weighing of grain; it merely designated private companies, trade groups and state agencies to weigh and sample grain. Inferior grades could be blended into a shipment and recorded weights could be greater than what was actually delivered.

No one knows how many millions of dollars were lost as exports exploded over the past seven years - particularly at busy Gulf ports where crews once worked 24 hours a day, seven days a week loading grain to keep pace with orders.

As the scandals were unraveled by federal prosecutors, principally in New Orleans, and by newspapers, Congress passed the Grain Standards Act of 1976.

That law created the grain inspection service, an Agriculture Department Agency that is expected to grow to 2,700 people (it has 780 now)and to cost $61.6 million in the budget year that begins Oct.1.

The agency was born last Nov.20 and on Jan.1, it took over official export weighing and sampling first at two New Orleans grain elevators - Bunge and Cook Industries - from the Destrehan Board of Trade. Both export firms are among the nine companies that have signed the anti-corruption agreements with the government.

Since then, export inspections in Toledo, Saginaw and Chicago have been assumed by the grain inspection service. Wilkinson said all four switchovers have gone smoothly.

By May 20, 1978, the nation's export inspections and weighings - complete with an official certificate of the weight - will be done almost entirely by the inspection service. The exceptions will be in 10 states that had state inspection agencies in operation last year. Export facilities in those 10 states (Virginia, Washington, Oregon, California, Minnesota, Wisconsin, Mississpi, Alabama, Florida and South Carolina) account for about 25 per cent of the nation's grain exports.

The grain inspection service is also drawing up regulations to tighten domestic weighing and inspections. It will name and supervise certain private firms, trade groups and state agencies as official inspectors - with the requirement that they have no connections with the grain trade.

Wilkinson told Congress, "We recently were told by Soviet grain officials that they are experiencing few quality problems now with grain they import from the United States. In their own words, there has been a 'marked improvement' in the quality of U.S. grain arriving at Soviet ports, with less infestation and less weed-seed contamination than before. That's a very good sign . . ."