Delano' does not only grieve the death of his brother, but also that his brother did not receive a proper Christian burial. Had his brother's body been preserved, this, theoretically, would have been possible, although quite belated. The secrecy and, to Western sensibilities, gruesome manner in which Aranda's remains were preserved by the Africans on board further exacerbates the suggestion that they are inhumane and amoral. See this article in Vol. 8 of Sharpe's London Magazine (1849) for perspectives on the burial practices of "barbarous nations" contemporary to the composition of Benito Cereno.

Western embalming techniques were first developed in 16th century England for scientific purposes; at the time this story is set, embalming the dead was a more common practice.

"The English physician William Harvey created the modern method of embalming in the 17th century. This method involves injecting chemicals into a dead body's arteries to keep the body from decaying. Up until the middle of the 18th century, embalming was used mostly in science and medicine. However, in the mid-18th century, the Scottish surgeon William Hunter used Harvey's methods to preserve bodies in morgues. His brother, John Hunter, was the first to advertise embalming to regular people who wanted to see their loved ones' bodies preserved after death." https://simple.wikipedia.org/wiki/Embalming#The_17th_and_18th_centuries